Pipe fittings and pipes with pipe fittings

Abstract

The pipe joint has: a zinc-based coating; and a resin coating located on the outermost surface outside the zinc-based coating, including a polyethylene-based substance, a lubricant, and solid particles. When defining the average plating thickness t of the joint related to the thickness of the zinc-based coating, 2.1 < t < 19.7 holds.

Description

Technical Field

[0001] The present disclosure relates to a pipe joint and a pipe with the pipe joint. Background Art

[0002] In order to prevent threaded parts such as standard bolts or nuts from loosening or to increase axial force, it is well known that lubricants or adhesives are applied to the surface of threaded parts, or surface treatments such as plating are performed. In addition, a technology for applying resin coating to threaded pipe joints used in automobile brake pipes and the like is known (for example, refer to Japanese Patent Publication No. 2015-230099, Japanese Patent Publication No. 2009-299895, and European Patent Application Publication No. 2706277).

[0003] If the tightening torque of the threaded component to the object component is constant, the smaller the friction between the threaded component and the object component, the greater the axial force. Here, the threaded component is subjected to surface treatment to reduce the friction. As a result, a larger axial force can be obtained with the same tightening torque. This is not limited to standardized threaded components, but also applies to threaded pipe joints. Summary of the invention

[0004] When a pipe joint is used to connect metal pipes, an annular portion called an ISO flare nut or a double flare nut is formed at the end when the pipe joint is installed on the outer periphery of the pipe. The annular portion protrudes outward in the pipe diameter and is larger than the inner diameter of the pipe joint, so the pipe joint is prevented from falling off at the end by the annular portion. In addition, the pipes used for automobile piping are bent according to the layout of the bottom of the vehicle, so the pipe joint is also prevented from falling off in a direction away from the end by the pipe bending portion. Therefore, when the connection of the pipe joint is loosened in order to repair or maintain various devices connected to the pipe, and the pipe is removed to restore the status quo, unless the pipe joint is replaced together with the pipe, the same pipe joint has to be used again for each maintenance or repair.

[0005] When the pipe joint is repeatedly connected and released at the same tightening torque in order to reuse it, there is a tendency that the axial force decreases as the number of times increases. Therefore, when the pipe joint is connected at the same tightening torque when it is reused, the greater the axial force reduction rate is, the lower the axial force is, and therefore the reused pipe joint may not be able to obtain the desired connection force.

[0006] On the other hand, when the pipe joint is coupled, a heel rotation may occur in which the pipe rotates together with the pipe joint. Heel rotation occurs when the friction force generated between the annular portion provided on the pipe and the pipe joint is greater than the friction force generated between the annular portion and the object part. In order to prevent this heel rotation, the pipe joint is coupled while the pipe is fixed. At this time, a heel rotation torque that twists the pipe is generated as a reaction force to prevent heel rotation. If the heel rotation torque is large, the pipe will be damaged. In addition, the reaction force of the heel rotation torque acts in the direction of loosening the coupled pipe joint. Therefore, if the heel rotation torque remains when the pipe is installed in the vehicle, the vibration of the vehicle will induce the pipe joint to loosen. Therefore, the upper limit of the heel rotation torque generated when the pipe joint is coupled should be determined in consideration of the pipe strength and the vibration of the vehicle.

[0007] Regarding the follow-up torque, its tendency is that it is the largest when the pipe joint is first connected, decreases when it is used next time, and does not change much depending on the number of times it is used thereafter. Therefore, if the follow-up torque is less than the upper limit value when the pipe joint is first connected, the follow-up torque will not exceed the upper limit value when the pipe joint is used again.

[0008] It is known that the purpose of applying zinc plating to pipe joints is to improve corrosion resistance or to make the surface where the resin coating is provided smooth by plating to stabilize the axial force. The inventors of the present invention have found that the thickness of the zinc plating layer inside the resin coating affects the axial force reduction rate caused by the reuse of the pipe joint and the heel torque at the time of the initial connection during the study of the reuse of the pipe joint.

[0009] Here, an object of the present disclosure is to provide a pipe joint and a pipe with the pipe joint, which can obtain an initial axial force with a follow-up torque less than an upper limit value and can suppress the axial force reduction rate to a low level when repeatedly connected and released.

[0010] The pipe joint of the present invention is assembled on the outer circumference of a metal pipe, wherein the metal pipe is provided with an annular portion protruding radially outward at the end thereof, and the pipe joint is connected to an object component while being in contact with the annular portion, so that the pipe can be connected to the object component. The pipe joint comprises: a threaded portion having a male thread formed thereon, the male thread meshing with a female thread provided on the object component; a head portion provided at one end side of the threaded portion, into which a tightening torque is inputted when connected; and a contact portion provided at the other end side of the threaded portion, for contacting the annular portion while connecting the pipe to the object component when connected. The annular portion is pressed against the object part; a zinc-based plating layer, which is provided on the threaded portion, the head portion and the contact portion; and a resin coating, which is located on the outermost surface outside the zinc-based plating layer, including a polyethylene-based substance, a lubricant and solid particles, the threaded portion, the head portion and the contact portion respectively pass through a through hole, and the through hole extends in a direction parallel to the direction of travel of the male thread during engagement, the male thread of the threaded portion has an outer diameter of 9.53 to 14.0 [mm], and the head portion includes a first plane facing in the opposite direction of the travel direction and a plane orthogonal to the first plane. The contact portion includes a contact surface capable of contacting the annular portion and has an inner diameter of 4.98 to 8.44 [mm], and in a cross section including a center line extending in the same direction as the through hole and orthogonal to the second plane of the head, when the number of thread teeth constituting the male thread is counted from the head side, the first thread tooth is defined as the first thread tooth, the second thread tooth is defined as the second thread tooth, the third thread tooth is defined as the third thread tooth, and the fourth thread tooth is defined as the fourth thread tooth, and in the cross section, the number of thread teeth constituting the male thread is defined as the first thread tooth, the second thread tooth is defined as the second thread tooth, the third thread tooth is defined as the third thread tooth, and the fourth thread tooth is defined as the fourth thread tooth. The first area set on the plane, the second area set on the second plane of the head, the third area set on the rear side of the third thread, the fourth area set on the rear side of the fourth thread, and the fifth area set on the contact surface of the contact portion, and when the five calculated values ​​are defined as X1, X2, X3, X4, and X5, and the four measured values ​​are defined as T1, T2, T3, and T4, when the value obtained by (X1+X2+X3+X4+X5+T1+T2+T3+T4) / 9 is defined as the average plating thickness t [μm] of the joint, 2.1 <t<19.7 is established, wherein the five calculated values ​​are obtained by calculating the arithmetic average of the thickness of the zinc-based plating layer measured at seven points arranged unidirectionally at intervals of 10 [μm] in each of the first region to the fifth region, and the four measured values ​​are obtained by measuring the thickness of the zinc-based plating layer at the root between the second thread and the third thread, the top of the third thread, the root between the third thread and the fourth thread, and the top of the fourth thread in the cross section. .

[0011] The pipe with a pipe joint disclosed in the present invention comprises: a metal pipe, an annular portion protruding outward in the pipe radial direction is provided at the end thereof, and a bent portion is provided at a position away from the annular portion; and a pipe joint, which is assembled on the outer periphery of the pipe in a state where it is prevented from falling off by the annular portion and the bent portion, and is coupled to an object component in a state where it is in contact with the annular portion, thereby enabling the pipe to be coupled to the object component, the pipe joint comprising: a threaded portion, which is formed with a male thread, and the male thread meshes with a female thread provided on the object component; a head, which is provided at one end side of the threaded portion, and to which a tightening torque is input when coupled; and a contact portion, which is provided at The other end side of the threaded portion is used to contact the annular portion and push the annular portion to the object part while being connected to the object part; a zinc-based plating layer is provided on the threaded portion, the head portion and the contact portion; a resin coating is located on the outermost surface outside the zinc-based plating layer, and includes a polyethylene-based substance, a lubricant and solid particles. The threaded portion, the head portion and the contact portion respectively pass through through holes, and the through holes extend in a direction parallel to the direction of travel of the male thread during connection. The male thread of the threaded portion has an outer diameter of 9.53 to 14.0 [mm], and the head portion includes a A first plane in the direction opposite to the traveling direction and a second plane orthogonal to the first plane, the contact portion includes a contact surface capable of contacting the annular portion and has an inner diameter of 4.98 to 8.44 [mm], and in a cross section including a center line extending in the same direction as the through hole and orthogonal to the second plane of the head, when the number of thread teeth constituting the male thread is counted from the head side, the first thread tooth is defined as the first thread tooth, the second thread tooth is defined as the second thread tooth, the third thread tooth is defined as the third thread tooth, and the fourth thread tooth is defined as the fourth thread tooth, and in the cross section, the number of thread teeth constituting the male thread is defined as the first thread tooth, the second thread tooth is defined as the second thread tooth, the third thread tooth is defined as the third thread tooth, and the fourth thread tooth is defined as the fourth thread tooth. The first area set at the first plane of the head, the second area set at the second plane of the head, the third area set at the rear side of the third thread, the fourth area set at the rear side of the fourth thread, and the fifth area set at the contact surface of the contact portion, and when five calculated values ​​are defined as X1, X2, X3, X4, and X5, and four measured values ​​are defined as T1, T2, T3, and T4, when the value obtained by (X1+X2+X3+X4+X5+T1+T2+T3+T4) / 9 is defined as the average plating thickness t [μm] of the joint, 2.1 <t<19.7 is established, wherein the five calculated values ​​are obtained by calculating the arithmetic average of the thickness of the zinc-based plating layer measured at seven points arranged unidirectionally at intervals of 10 [μm] in each of the first region to the fifth region, and the four measured values ​​are obtained by measuring the thickness of the zinc-based plating layer at the root between the second thread and the third thread, the top of the third thread, the root between the third thread and the fourth thread, and the top of the fourth thread in the cross section. .

[0012] Another pipe joint disclosed in the present invention is assembled on the outer circumference of a metal pipe, wherein the metal pipe is provided with an annular portion protruding radially outward of the pipe at the end thereof, and the pipe joint can be connected to the object component by connecting to the object component in a state of contact with the annular portion, and the pipe joint comprises: a threaded portion, which is formed with a male thread, and the male thread meshes with a female thread provided on the object component; a head, which is provided on one end side of the threaded portion and inputs a tightening torque when connecting; a contact portion, which is provided on the other end side of the threaded portion and is used to contact with the annular portion and push the annular portion to the object component when connecting to the object component; a zinc-based plating layer, It is provided on the threaded portion, the head portion and the contact portion; and a resin coating, which is located on the outermost surface outside the zinc-based plating layer, including polyethylene-based substances, lubricants and solid particles. The threaded portion, the head portion and the contact portion respectively pass through through holes, and the through holes extend in a direction parallel to the direction of travel of the male thread during engagement. The male thread of the threaded portion has an outer diameter of 9.53 to 14.0 [mm]. The head portion includes a first plane facing in the opposite direction to the direction of travel and a second plane orthogonal to the first plane. The contact portion includes a contact surface capable of contacting the annular portion and has a diameter of 4.98 to 8.The inner diameter is 44 [mm]. The range of the average plating thickness t of the joint is set as follows: in a cross-section including a center line extending in the same direction as the through hole and orthogonal to the second plane of the head, when counting the number of thread teeth forming the male thread from the head side, the first thread tooth is defined as the 1st thread tooth, the second thread tooth is defined as the 2nd thread tooth, the third thread tooth is defined as the 3rd thread tooth, and the fourth thread tooth is defined as the 4th thread tooth. In this cross-section, a 1st region set on the 1st plane of the head, a 2nd region set on the 2nd plane of the head, a 3rd region set on the rear side of the 3rd thread tooth, a 4th region set on the rear side of the 4th thread tooth, and a 5th region set on the contact surface of the contact portion are defined. And, when defining five calculated values as X1, X2, X3, X4, X5 and four measured values as T1, T2, T3, T4, the value obtained by (X1 + X2 + X3 + X4 + X5 + T1 + T2 + T3 + T4) / 9 is defined as the average plating thickness t [μm] of the joint. Among them, the five calculated values are obtained by calculating the arithmetic mean of the thicknesses of the zinc-based coating measured at seven points arranged unidirectionally at 10 [μm] intervals in each of the 1st region to the 5th region for the 1st region to the 5th region respectively. The four measured values are obtained by measuring the thicknesses of the zinc-based coating at the bottom of the tooth between the 2nd thread tooth and the 3rd thread tooth, the top of the 3rd thread tooth, the bottom of the tooth between the 3rd thread tooth and the 4th thread tooth, and the top of the 4th thread tooth in the cross-section. And, when repeating the coupling test including the coupling operation and the decoupling operation n times (where 1 < n < 6), the maximum axial force generated in the 1st coupling test is defined as the initial axial force F1 [kN], and the maximum axial force generated in the nth coupling test is defined as the nth axial force F. n [kN], and when the value obtained by -(F n - F1) / (n - 1) is defined as the axial force reduction rate α [kN / time], 10.0 < F1 < 14.0 and 0 < α < 1.75 are satisfied. Among them, in the coupling operation, a test component equivalent to the target component and a test pipe having the same outer diameter as the pipe and a test ring equivalent to the annular portion are prepared, and they are coupled with the test component with a tightening torque in the range of 12.0 to 22.0 [Nm] in a state of being in contact with the test ring. In the decoupling operation, the coupling is loosened after the coupling operation to release the coupling of the test pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 FIG. is a view showing a state of a plurality of brake pipes after the pipe joint is assembled, assembled, and bent.

[0014] Figure 2 It is a figure which shows the open nut as an example of a pipe joint.

[0015] Figure 3 This is a diagram showing a brake pipe in which an ISO open nut is formed at the end as an example of an annular portion.

[0016] Figure 4 This is a diagram showing a state where a brake pipe is connected to a master cylinder as an example of a target component.

[0017] Figure 5 yes Figure 2 Enlarged cross-sectional view of the V portion.

[0018] Figure 6 This is a diagram showing an open nut as another example of a pipe joint.

[0019] Figure 7 This is a diagram showing a brake pipe in which a double open nut is formed at the end as another example of the annular portion.

[0020] Figure 8 is with Figure 7 A cross-sectional view of a portion of a master cylinder as an example of a target component to which a brake pipe is combined.

[0021] Fig. 9 yes Figure 6 An enlarged cross-sectional view of section IX.

[0022] Fig.10 It is a diagram showing a list of test samples.

[0023] Fig.11A This is a diagram showing a cross section that serves as a reference for measuring the plating thickness of the open nut according to the first embodiment.

[0024] Fig. 11B This is a diagram showing a part of a cross section serving as a reference for measuring the plating thickness of the open nut according to the second embodiment.

[0025] Fig. 11C This is a diagram showing a method for measuring the plating thickness in each region.

[0026] Fig.12 It is a diagram showing the structure of an axial force measuring device.

[0027] Fig.13 It is a graph showing the test results of the bonding test.

[0028] Fig.14 This is a graph that summarizes the evaluation results to sort out qualified samples and unqualified samples. DETAILED DESCRIPTION

[0029] The components indicated by the same reference numerals in the drawings are the same or similar components. In addition, the descriptions and reference numerals repeated in the embodiments described below may be omitted.

[0030] For example, automobile brake pipes are used as pipes for transmitting the pressure generated in the master cylinder to the brake units installed at each wheel. In many cases, an ABS unit or an ESC unit is installed from the master cylinder to the brake unit, and the brake pipe is also used to connect these units. Multiple brake pipes of different diameters are selected based on many conditions such as the pressure resistance conditions required between these units.

[0031] like Figure 1 As shown in FIG. 1 , a plurality of brake pipes BT are gathered by a jig C made of resin, for example, and are supplied to the automobile assembly line as assembled products after being bent according to the layout of the automobile bottom. In order to withstand the working pressure of the brake, each brake pipe BT is made of a double-wound pipe made of a metal plate such as a steel plate and having excellent pressure resistance. In the case of the brake pipe, as an example, the outer diameter is selected The diameter of the pipe is within the range of 4.76 to 8.00 [mm]. In each brake pipe BT, an open nut FN suitable for its outer diameter is installed. In the automobile assembly line, the operator combines the above-mentioned units with the open nuts FN installed in each brake pipe BT at a predetermined common tightening torque, thereby centrally implementing the connection of the brake pipe BT.

[0032] In a state where the open nut FN is mounted, the end of each brake pipe BT is subjected to high-pressure end processing. As the high-pressure end processing, there is the end processing that forms an annular portion Rp such as ISO open end specified by the International Organization for Standardization (ISO) or double open end specified by the Japan Automobile Technical Association Standard (JASO). In a state where the open nut FN is mounted on the outer periphery of each brake pipe BT, the end processing that forms the annular portion Rp and the bending processing that forms the bent portion Bp are performed. Therefore, the open nut FN is prevented from falling off the brake pipe BT by the annular portion Rp and the bent portion Bp provided at a position away from the annular portion Rp.

[0033] (First method)

[0034] Figure 2An open nut 1A suitable for ISO open end is shown in FIG. The open nut 1A is equivalent to an example of the pipe fitting disclosed in the present invention. The open nut 1A is a hollow pipe fitting, and is formed with a through hole 10 that can be inserted into a pipe. The open nut 1A includes: a threaded portion 12 formed with a male thread 12a; a head 13 provided on one end side of the threaded portion 12; and a contact portion 14 provided on the other end side of the threaded portion 12. These head 13, threaded portion 12 and contact portion 14 pass through the through hole 10 extending in the direction of the center line CL1. The through hole 10 of the open nut 1A shown in the figure is a shape having a certain inner diameter in the axial direction, but, for example, the through hole 10 can be replaced by a through hole with a stepped hole shape in which the inner diameter changes at a predetermined position in the axial direction.

[0035] The male thread 12a formed in the threaded portion 12 is, for example, similar to the female thread 12b (see Figure 4 ) are engaged, and the female thread 12b is a metric coarse screw thread standardized by ISO and is formed on the target part. However, as an example, the male thread 12a can also be changed to a metric fine crew thread of the same specification. The fine thread has a smaller thread lead angle than the coarse thread, so by changing to a fine thread, an open nut that is more difficult to loosen can be provided with the same axial force. In addition, as the size of the threaded portion 12 of the open nut 1A suitable for the above-mentioned brake pipe BT, there is a tendency that the larger the outer diameter of the pipe to be assembled, the larger the thread size is. Unless there are special circumstances, the size of the threaded portion 12 generally refers to a nominal diameter of M10 to M14, that is, an outer diameter of 10.0 to 14.0 [mm]. In addition, when the British quality thread is set on the open nut 1A, a thread with a nominal diameter in the range of 3 / 8 inch to 1 / 2 inch (about 9.53 to 12.7 [mm]) is used. Therefore, the outer diameter of the male thread 12a that can be used in the open nut 1A is within the range of 9.53 to 14.0 [mm].

[0036] The head 13 is a part to which the tightening torque is input when engaging, and has a standardized hexagonal shape so that it can be engaged with a common tool such as an open nut wrench. The head 13 includes: a hollow circular flat surface 13a facing the axial direction and six side surfaces 13b that are engaged with the tool. The flat surface 13a is equivalent to an example of the first plane, and any one of the six side surfaces 13b is equivalent to an example of the second plane. The size of the head 13 is selected based on the size of the threaded portion 12, but unlike the case of a standardized bolt head, it can be standardized to a certain extent in order to reduce the number of tool changes.

[0037] The contact portion 14 is provided along the center line CL1. Figure 2The right end of the male thread 12a is provided at the end of the male thread 12a on the side of the advancing direction when the male thread 12a is connected. The contact portion 14 has the following functions: when connected to the object part, one side is connected to the annular portion 16 formed as an ISO opening (see Figure 3 ) while pushing the annular portion 16 to the object part. The contact portion 14 includes a contact surface 14a in contact with the annular portion 16 and a cylindrical portion 14b extending from the threaded portion 12 to the end side. At the boundary between the contact portion 14 and the through hole 10, a chamfered portion 10a inclined at about 45° relative to the direction of the center line CL1 is provided. The chamfered portion 10a is used to alleviate the interference between the pipe exterior and the open nut 1A during the combination and the concentration of stress on the boundary between the through hole 10 and the contact portion 14. In addition, the chamfered portion 10a is presented in a cross section related to the center line CL1, and has a conical surface with a straight line as the ridgeline. Instead of the chamfered portion 10a, a processing portion may be provided, which has a curved surface with a curve as the ridgeline, and the curve is drawn by one or more arcs protruding on the center side.

[0038] The inner diameter of the contact portion 14 is determined by the inner diameter of the through hole 10. The inner diameter d of the contact portion 14 is, for example, When the outer diameter is 4.76[mm], it is set to 4.98[mm]. When the outer diameter is 6.0 [mm], it is set to 6.24 [mm]. When the outer diameter is 6.35[mm], it is set to 6.59[mm]. When the inner diameter d of the contact portion 14 is 8.0 [mm], it is set to 8.29 [mm]. As an example, the inner diameter d of the contact portion 14 allows an error of +0.15 [mm]. Therefore, the inner diameter d of the contact portion 14 that can be used in the open nut 1A is within the range of 4.98 to 8.44 [mm].

[0039] like Figure 3 As shown, the annular portion 16 is formed at the end of the brake pipe BT. An example of the formation steps is as follows. First, starting from the end, the resin coating layer BTa of the brake pipe BT is peeled off all over the circumference in a predetermined range in the direction of the tube axis Tx. Next, an annular portion 16 of an ISO open shape is formed at the end of the peeled portion BTb where the resin coating layer is peeled off, and the annular portion 16 protrudes outward in the tube radial direction orthogonal to the tube axis Tx. In addition, depending on the resin material of the resin coating layer BTa, the annular portion 16 may be formed at the end of the brake pipe BT without peeling off the resin coating layer BTa.

[0040] As an example of using the open nut 1A, Figure 4While explaining the case where the brake pipe BT is combined with the master cylinder MC1. The master cylinder MC1, as an example of an object component, has a housing 40. The housing 40 is provided with an insertion hole 41 for inserting the brake pipe BT. The insertion hole 41 is open to the outside of the housing 40, and the opposite side of the opening is connected to a liquid passage 42 formed in the housing 40. The liquid passage 42 is open at the bottom 43 of the insertion hole 41. The bottom 43 is formed in a shape that is retreated toward the inside of the device so as to be suitable for the shape of the annular portion 16 of the brake pipe BT. On the inner peripheral surface of the housing 40 formed with the insertion hole 41, a female thread 12b that meshes with the male thread 12a of the open nut 1A is formed.

[0041] First, the brake tube BT is inserted by making the annular portion 16 of the brake tube BT touch the bottom 43 of the insertion hole 41 while the open nut 1A is moved in a direction away from the end of the brake tube BT. In this state, the open nut 1A is brought close to the insertion hole 41 so that the male thread 12a of the threaded portion 12 is meshed with the female thread 12b of the housing 40. When the open nut 1A is rotated in the coupling direction, the contact portion 14 comes into contact with the annular portion 16. Therefore, when the open nut 1A is tightened while making the contact portion 14 come into contact with the annular portion 16, the annular portion 16 is pressed against the bottom 43 by the contact portion 14. While the open nut 1A is tightened, the annular portion 16 is sandwiched between the contact portion 14 and the bottom 43 and gradually deforms while starting from elastic deformation and changing to plastic deformation. As a result, the brake tube BT is fluid-tightly coupled to the master cylinder MC1. The coupling force of the brake tube BT is determined by the maximum axial force acting during such coupling operation.

[0042] In order to securely connect the brake pipe BT, Figure 5 As shown, a resin coating 18 is provided on the open nut 1A in order to increase the axial force during connection or to stabilize it. The open nut 1A has a zinc-based plating layer P1 formed on the metal texture M1. Furthermore, a resin coating 18 is provided on the plating layer P1. The resin coating 18 is located on the outermost surface outside the plating layer P1. In addition, as long as the resin coating 18 is located on the outermost surface, for example, different types of resin layers may be provided between the plating layer P1 and the resin coating 18. In order to form the plating layer P1, any one of zinc plating, zinc-iron alloy plating or zinc-nickel alloy plating may be implemented. In this method, a zinc-nickel alloy plating is provided as the plating layer P1. The plating layer P1 is provided on the entire metal texture M1. The plating layer P1 covers the surfaces of the threaded portion 12, the head 13 and the contact portion 14 and the inner circumferential surface of the through hole 10 passing through them.

[0043] In addition, the coating P1 may also be subjected to chemical conversion treatment. In this case, the coating P1 includes a chemical conversion treatment layer on its outside. According to the difference in the components of the chemical conversion treatment layer, there is a situation that is difficult to confirm even with a microscope. Through the chemical conversion treatment layer, the adhesion between the coating P1 and the resin coating 18 can be improved. The chemical conversion treatment layer may include metal atoms selected from titanium, zirconium, molybdenum, tungsten, vanadium, manganese, nickel, cobalt, chromium and lead. In addition, a part of these metal atoms may also be included in the chemical conversion treatment layer as compounds such as oxides. The chemical conversion treatment layer may also be a chromium-free chemical conversion treatment layer. The chemical conversion treatment step for forming the chemical conversion treatment layer may be a reaction type or a coating type, and may be a trivalent chromium chemical conversion treatment or a chromium-free chemical conversion treatment.

[0044] The plating layer P1 is formed by electrolytic plating. The untreated nut with the metal base M1 exposed is immersed in a plating bath containing metal ions of zinc and nickel. The thickness of the film deposited on the metal base M1 of the untreated nut is controlled by adjusting at least one of the current density defined as the current per unit area during the plating treatment and the treatment time.

[0045] In the case of electrolytic plating, the current density changes according to the shape of the plated product, so the thickness of the film formed on the plated product is not uniform. For example, the plated product includes not only parts with little shape change such as a flat surface or a cylindrical surface, but also parts with large shape change such as a convex corner or a pointed point on the surface side. In this case, the thickness of the film in each part is different. In the case of the open nut 1A, the thickness of the plating layer P1 is also different when comparing the top and bottom of the thread teeth of the threaded portion 12, or when comparing the top and the contact surface 14a of the contact portion 14. For example, there is a tendency that when comparing the thickness of the plating layer P1 between the top of the thread teeth of the threaded portion 12 and the contact surface 14a of the contact portion 14, the top thickness is smaller than the thickness of the contact surface 14a.

[0046] As will be described later, when the thickness of the plating layer P1 is different, the mechanical properties of the open nut 1A will change. However, since the thickness of the plating layer P1 varies depending on the location of the open nut 1A, it is not possible to accurately evaluate the correlation between the thickness of the plating layer P1 and the axial force and the mechanical properties. Here, the thickness of the plating layer P1 is quantitatively controlled and managed using the joint average plating thickness calculated by a predetermined method.

[0047] The resin coating 18 is formed at least on the coating region R (see Figure 2). As an example, the coating area R is set on the entire surface of the open nut 1A. That is, the coating area R is set on each surface of the threaded portion 12, the head 13 and the contact portion 14 of the open nut 1A and the inner circumferential surface of the open nut 1A through which the through hole 10 passes. The resin coating 18 includes a polyethylene-based substance, a lubricant and solid particles. The resin coating 18 is formed by attaching a coating agent C including them as a component to the coating area R. As the polyethylene-based substance, for example, polyethylene or a polyethylene copolymer can be selected. As the lubricant, for example, any one of polyethylene wax, molybdenum disulfide, graphite or boron nitride or any combination thereof can be selected. The lubricant can be solid or liquid. In addition, as fixed particles, for example, any one of silicon dioxide, silicon nitride or titanium nitride or any combination thereof can be selected.

[0048] The resin coating 18 is formed by a dip coating method, for example. Alternatively, the resin coating 18 may be formed by a spray coating method in which the coating agent is finely sprayed. The spray coating method is suitable for partially forming the resin coating 18 with respect to the open nut 1A. In addition, the friction coefficient of the resin coating 18 is smaller than the friction coefficient of the plating layer P1.

[0049] (Second method)

[0050] Figure 6 The open nut 1B suitable for double opening is shown. The open nut 1B is equivalent to an example of the pipe joint disclosed in the present invention. The open nut 1B is a hollow pipe joint, and is formed with a through hole 20 that can be inserted into a pipe. The open nut 1B includes: a threaded portion 22, which is formed with a male thread 22a; a head 23, which is provided on one end side of the threaded portion 22; and a contact portion 24, which is provided on the other end side of the threaded portion 22. These head 23, threaded portion 22 and contact portion 24 pass through the through hole 20 extending in the direction of the center line CL2. In the case of the open nut 1B, the through hole 20 is a shape having a certain inner diameter along the axial direction, but, for example, instead of the through hole 20, it is also possible to change it to a through hole with a stepped hole shape in which the inner diameter changes at a predetermined position in the axial direction.

[0051] The male thread 22a formed in the threaded portion 22 has the same specification requirements as the male thread 12a of the threaded portion 12 provided in the open nut 1A of the first embodiment, and the outer diameter of the male thread 22a that can be adopted as the open nut 1B is within the range of 9.53 to 14.0 [mm]. In addition, the specification requirements of the head 23 are also the same as the specification requirements of the head 13 of the open nut 1A. The head 23 includes a hollow circular flat surface 23a facing the axial direction and six side surfaces 23b that are engaged by the tool. The flat surface 23a is equivalent to an example of the first plane, and one of the six side surfaces 23b is equivalent to an example of the second plane. The specification requirements of the contact portion 24 are also the same as the specification requirements of the contact portion 14 of the open nut 1A, and the inner diameter d of the contact portion 24 that can be adopted as the open nut 1B is within the range of 4.98 to 8.44 [mm].

[0052] The contact portion 24 is provided along the center line CL2. Figure 6 The right end of the male thread 22a is provided at the end of the male thread 22a on the side of the advancing direction when the male thread 22a is connected. The contact portion 24 has the following functions: when the counterpart is connected, it is connected to the annular portion 26 (see Figure 7 ) while contacting the annular portion 26 to the counterpart. In the case of the open nut 1B, the contact portion 24 is provided near the terminal end of the threaded portion 22. There is no cylindrical portion 14b (see Figure 2 ) as a clear cylindrical portion. However, as an open nut suitable for double opening, some also include a cylindrical portion equivalent to the cylindrical portion 14b. The contact portion 24 has a conical contact surface 24a with an inclination angle of about 42° relative to the axial direction.

[0053] like Figure 7 As shown, the annular portion 26 is formed at the end of the brake pipe BT. An example of the formation steps is as follows. First, starting from the end, the resin coating layer BTa of the brake pipe BT is peeled off all over the circumference in a predetermined range in the direction of the tube axis Tx. Next, a double-open annular portion 26 is formed at the end of the peeled portion BTb where the resin coating layer BTa is peeled off, and the annular portion 26 protrudes outward in the tube radial direction orthogonal to the tube axis Tx. In addition, depending on the resin material of the resin coating layer BTa, the annular portion 26 may be formed at the end of the brake pipe BT without peeling off the resin coating layer BTa.

[0054] On the counterpart member to be joined to the brake pipe BT having the annular portion 26, a Figure 8The insertion hole 51 of the structure shown. For example, the insertion hole 51 is formed in the master cylinder MC2 as an example of the target component. The insertion hole 51 opens to the outside of the housing 50, and the opposite side of the opening is connected to the liquid passage 52 formed in the housing 50. The liquid passage 52 opens to the bottom 53 of the insertion hole 51. The bottom 53 is formed in a shape protruding to the outside of the device in a manner suitable for the shape of the annular portion 26 of the brake pipe BT. The female thread 22b that meshes with the male thread 22a of the open nut 1B is formed on the inner peripheral surface of the housing 50 where the insertion hole 51 is formed. Since the connection of the brake pipe BT using the open nut 1B is the same as the case of the open nut 1A, the description is omitted.

[0055] like Fig. 9 As shown, a resin coating 28 is provided on the open nut 1B. The open nut 1B forms a zinc-based plating layer P2 on the metal texture M2. Furthermore, a resin coating 28 is provided on the plating layer P2. The resin coating 28 is located on the outermost surface outside the plating layer P2. In addition, as long as the resin coating 28 is located on the outermost surface, for example, a different type of resin layer may be provided between the plating layer P2 and the resin coating 28. In order to form the plating layer P2, any one of zinc plating, zinc-iron alloy plating or zinc-nickel alloy plating may be implemented. In this method, a zinc-nickel alloy plating layer is provided as the plating layer P2. The plating layer P2 is provided on the entire surface of the metal texture M1. The plating layer P2 covers the surfaces of the threaded portion 22, the head 23 and the contact portion 24 and the inner circumferential surface of the through hole 20 passing through them. The plating layer P2 may also include a chemical treatment layer on the outside. As in the first method, for example, the plating layer P2 may be formed by electrolytic plating and the resin coating 28 may be formed by dip coating. Furthermore, the friction coefficient of the resin coating layer 28 is smaller than the friction coefficient of the plating layer P2.

[0056] [Example]

[0057] For each of the open nuts 1A and 1B, there is a tendency that the axial force during the connection decreases as the number of repetitions increases by repeating connection and release based on the same tightening torque. Therefore, it can be seen that the thickness of the zinc-based plating layer is a factor that affects the axial force reduction rate according to the connection test described below. In addition, since no significant difference was found between the open nut 1A and the open nut 1B in the test results of the connection test, the test results implemented on the open nut 1A are disclosed below.

[0058] 1. Test samples

[0059] (1) Preparation of test samples

[0060] like Fig.10As shown, for three types of open nuts with different shapes or sizes, a plurality of samples with different average plating thicknesses t [μm] of the joints described below were prepared. As an example of the plating layer of each sample, a zinc-nickel alloy plating layer was used. In addition, by adjusting at least one of the current density and the treatment time during the plating treatment of each sample, the average plating thickness t of the joints was made different from each other. That is, the parameters for controlling the average plating thickness t of the joints are the current density and the treatment time.

[0061] The resin coating of each sample includes the above-mentioned polyethylene-based substance, lubricant, and solid particles, and is formed by attaching either of two coating agents C1 and C2 with different viscosities at 25 [°C] to the coating area. As a method for forming the resin coating, a dip coating method was used. Regarding the thickness of the resin coating, the thickness is managed using the unit area mass w [g / m2] related to this thickness described below. The unit area mass w of each sample was adjusted to be within the range of 0.79 < w < 10.07.

[0062] (2) Average plating thickness of the joint

[0063] In terms of electroplating characteristics, the thickness of the plating layer is different depending on the part of the open nut. It is known that the thickness of the plating layer affects the mechanical characteristics of the open nut such as the axial force. Here, the average plating thickness t [μm] of the joint is used to quantitatively control and manage the thickness of the plating layer. The average plating thickness t of the joint is calculated according to the following procedure.

[0064] Fig.11A A cross-section of the open nut 1A passing through the center line CL1 and orthogonal to any two of the six side surfaces 13b of the head 13 is shown. The plating thickness of each part presented in this cross-section is measured to calculate the average plating thickness t of the joint.

[0065] (a) The number of thread teeth R i (where i = 1, 2, 3, 4...) that form the male thread 12a counted from the head 13 side. The first one is defined as the first thread tooth R1, the second one is defined as the second thread tooth R2, the third one is defined as the third thread tooth R3, and the fourth one is defined as the fourth thread tooth R4.

[0066] (b) Set the following five regions Ar i (where i = 1, 2, 3, 4, 5).

[0067] (b1) The first region Ar1

[0068] The first region Ar1 is a region set on the flat surface 13a of the head 13. As Fig.11A shown, the first region Ar1 has the distance from the center line CL1 to the inner peripheral surface of the through hole 10 as r 11The distance from the center line CL1 to the side 13b is r 12 In the case of 11 +r 12 ) / 2 is within a circle with a radius of 100 [μm] as the center.

[0069] (b2) Second region Ar2

[0070] The second area Ar2 is an area set on the side surface 13b of the head 13. Fig.11A As shown, when the distance from the flat surface 13a to the end of the side surface 13b is L2, the second area Ar2 is set within a circle with a radius of 100 [μm] centered at a position L2 / 2 away from the flat surface 13a.

[0071] (b3) The third area Ar3

[0072] The third region Ar3 is set within a circle having a radius of 100 [μm] centered at the midpoint of the rear side surface of the third thread crest R3.

[0073] (b4) 4th region Ar4

[0074] The fourth area Ar4 is set within a circle having a radius of 100 [μm] centered at the midpoint of the rear side surface of the fourth thread crest R4.

[0075] (b5) Fifth region Ar5

[0076] The fifth area Ar5 is an area set on the contact surface 14a of the contact portion 14. Fig.11A As shown in FIG. 1 , the fifth region Ar5 has a distance from the center line CL1 to the inner peripheral surface of the through hole 10 (the inner diameter of the contact portion 14) as r 51 The distance from the center line CL1 to the outer peripheral surface of the contact portion 14 is r 52 In the case of 51 +r 52 ) / 2 is within a circle with a radius of 50 [μm] centered at the position. In the case of the open nut 1B, the first region Ar1 to the fourth region Ar4 are the same as those of the open nut 1A, but the fifth region Ar5 is as follows: Fig. 11B Set as shown. Fig. 11B A portion of the cross section of the open nut 1B passing through the center line CL2 and orthogonal to any two of the six side surfaces 23b of the head 23. The fifth area Ar5 in this case is set within a circle with a radius of 100 [μm] centered at the midpoint of the contact surface 24a of the contact portion 24 shown in the cross section.

[0077] (c) In each area Ar set in (b) abovei Inside, such as Fig. 11C As shown in the figure, the coating thickness is measured at 7 points p1 to p7 arranged in one direction at intervals of 10 [μm], and the area Ar i The arithmetic mean of these seven measured values ​​is calculated. i The corresponding five calculated values ​​are X1, X2, X3, X4, and X5.

[0078] (d) The plating thickness is measured at the root M1 between the second thread R2 and the third thread R3, the crest M2 of the third thread R3, the root M3 between the third thread R3 and the fourth thread R4, and the crest M4 of the fourth thread R4. Four measured values ​​T1, T2, T3, and T4 corresponding to these portions M1 to M4 are obtained.

[0079] (e) The joint average plating thickness t is calculated based on the following formula 1.

[0080] t=(X1+X2+X3+X4+X5+T1+T2+T3+T4) / 9……1

[0081] (f) When measuring the coating thickness, first, use a cutter to cut the actual open nut 1A or the actual open nut 1B in the longitudinal direction. During the cutting, the biting position of the cutting knife is offset slightly from the center line to the radius in a manner that exceeds the center line of the actual object without being over-ground in the grinding step described later. In this way, a measuring piece that is slightly larger than half while ensuring the grinding allowance can be obtained. Next, a resin is used to cast a mold in a manner that covers the measuring piece. After molding, the cross-sectional direction of the measuring piece is known in advance. Next, a grinding disc is used to grind the plane of the measuring piece molded by the resin until a surface containing Fig.11A or Fig. 11B Therefore, as an example, each part of the polished cross section is photographed at a magnification of 1000 to 2500 times using the following digital microscope, and the plating thickness is measured based on the photographed image.

[0082] Model: OLYMPUS DSX 510

[0083] Manufacturer: Olympus Corporation

[0084] (3) Calculation of mass per unit area

[0085] The thickness of the resin coating is related to the mass of the substance attached to the coating area. Here, as a physical quantity related to the thickness of the resin coating, the value obtained by dividing the mass difference between the presence and absence of the resin coating by the surface area of ​​the coating area is defined as the unit area mass w [g / m 2 ]. The thickness of the resin coating is quantified using the mass per unit area w.

[0086] The mass per unit area w is calculated by dividing the mass difference between the mass of the open nut before the resin coating treatment and the mass of the open nut after the resin coating is formed by dividing the mass difference between the mass of the open nut after the resin coating is formed by dividing the mass difference between the mass of the open nut after the resin coating is removed by the entire surface area of ​​the open nut. As a method for removing the resin coating, for example, there is a method in which the open nut after the resin coating is immersed in a high-temperature organic solvent, and then the immersed open nut is used for washing and drying with an organic solvent prepared separately for washing. As an organic solvent for immersing the open nut, for example, an organic solvent obtained by dissolving polyethylene such as benzene or decalin can be used. The immersion time or drying time is set to a degree that the open nut before the resin coating treatment can be treated the same as the open nut before the resin coating treatment. For example, the immersion time in the organic solvent can be set to 5 hours, and after washing with the organic solvent for washing, the drying time is set to 1 hour. The open nut after the resin coating is removed by such a treatment can be treated the same as the open nut before the resin coating treatment.

[0087] The total surface area of ​​the open nut is calculated based on the design drawing data of the open nut using the surface area calculation function of the CAD software. By using this function, the surface area can be calculated for any range of the open nut. In addition, depending on the CAD software, the calculated value of the surface area may sometimes have some differences, but this difference can be ignored when the unit area mass w is calculated to 2 decimal places. In addition, the error of the calculated value based on the calculated value of the CAD software and the three-dimensional measurement of the actual external dimensions, and the calculated value based on the measurement data is also just negligible.

[0088] (4) Sample number

[0089] like Fig.10 As shown in FIG. 1 , sample numbers #101 to #209 are assigned to the samples to distinguish them from each other. In addition, the first digit of the sample number is assigned in accordance with the type of the coating agent C1 or C2.

[0090] 2. Combined test methods

[0091] (1) Axial force measurement device

[0092] To measure the axial force of each sample, the Fig.12 The axial force measuring device shown. Fig.12The structure of the axial force measuring device 100 is schematically shown. A test pipe T corresponding to the brake pipe BT is placed on the axial force measuring device 100. The test pipe T is placed on the axial force measuring device 100 in such a manner that its pipe axis Tx and the reference axis SAx are consistent. A sample S with an open nut is assembled on the test pipe T, and a test annular portion TR is formed at the end of the test pipe T. The axial force measuring device 100 performs a tightening operation on the sample S until a specified tightening torque is reached, and connects the test pipe T to a test component TM corresponding to the target component. During the tightening operation, the axial force measuring device 100 measures the axial force or other physical quantities of the sample S.

[0093] The axial force measuring device 100 includes a frame 101, which is installed, for example, on the floor of a test room. The frame 101 of the axial force measuring device 100 includes a tightening operation unit 102 for tightening the sample S, an object component holding unit 103 for holding the test component TM, and a tube holding unit 104 for holding the test tube T. The tightening operation unit 102, the object component holding unit 103, and the tube holding unit 104 are arranged on the frame 101 in a manner arranged along the reference axis SAx direction.

[0094] The tightening operation unit 102 includes a tool 110 that is engaged with the head of the sample S, a motor 111 that drives the tool 110 to rotate about the reference axis SAx, and a tightening torque sensor 112 that outputs a signal corresponding to the driving resistance of the tool 110 .

[0095] The object component holding portion 103 holds the test component TM using the first fixture 103a and the second fixture 103b divided along the reference axis SAx direction. The test component TM is divided along the reference axis SAx direction, and a first part TMa is held by the first fixture 103a, and another second part TMb is held by the second fixture 103b. The first part TMa has a threaded hole 115, and the threaded hole 115 is formed with a female thread 115b that engages with the male thread of the sample S. The second part TMb has a bottom 116 of the test annular part TR of the push test pipe T. After the threaded hole 115 and the bottom 116 are concentrically connected, they become a hole shape equivalent to the above-mentioned insertion holes 41 and 51. The first fixture 103a and the second fixture 103b can be held in a state where the threaded hole 115 of the first part TMa and the bottom 116 of the second part TMb are concentrically connected. The first jig 103a is fixed to the frame 101. On the other hand, the second jig 103b abuts against the first portion TMa and the second portion TMb, and is restricted in the direction of the reference axis SAx while sandwiching the load sensor 117.

[0096] The tube holding unit 104 includes: a fixing mechanism 118 that clamps a fixed position set at a predetermined distance (e.g., 0.3 [m]) from the end of the test tube T; and a rotation torque sensor 119 that outputs a signal corresponding to the torque generated by the fixing mechanism 118 rotating around the reference axis SAx.

[0097] When the sample S is tightened by the tightening operation part 102, the sample S moves while being engaged with the female thread 115b formed on the first part TMa of the test component TM, and the test annular part TR is pressed by the bottom 116 formed on the second part TMb. As a result, a force that pulls the first part TMa and the second part TMb apart from each other in the reference axis SAx direction acts on them. The first part TMa is held by the first clamp 103a fixed to the frame 101 and is in a state where it cannot move in the reference axis SAx direction. On the other hand, the second part TMb is held by the second clamp 103b and is restricted in the reference axis SAx direction in a state where the load cell 117 is clamped. Therefore, the load acting on the second part TMb is equivalent to the reaction force of the axial force of the sample S, so the detection value of the load cell 117 can be treated as the measured value of the axial force. That is, the axial force of the sample S can be directly measured based on the output signal of the load sensor 117 without relying on calculation based on the tightening torque. The respective signals of the tightening torque sensor 112, the load sensor 117, and the heel-torque sensor 119 are input to the control device 120. The control device 120 can be a personal computer as an example. The control device 120 performs a predetermined process on the input signals from each sensor, and stores the data that establishes a corresponding relationship between the tightening torque of the input sample S, the axial force, and the heel-torque as the measurement result, and can output the measurement result to an output unit such as a display as needed.

[0098] (2) Test methods

[0099] use Fig.12The axial force measuring device 100 shown above assembles an unused sample S to an unused test pipe T, performs the above-mentioned joining operation, and then performs a disassembly operation. The fastening operation part 102 loosens the sample joining to disassemble the test part TM of the test pipe T. In addition, it is restored to the initial value (for example, 0.0 [kN]) according to the detection value of the load sensor 117 to judge that the joining of the test pipe T is disassembled. The fastening torque during the joining of the fastening operation part 102 is set, as an example, to a value within the range of 12.0 [Nm] to 22.0 [Nm], for example, set to 17.0 [Nm]. The above operations are regarded as the first joining test, and without replacing the test pipe T and the sample S, the joining test including the fastening operation, the measurement of the axial force, etc., and the disassembly operation is repeated a total of 5 times. In each joining test, the axial force and the rotation torque are obtained and recorded by the axial force measuring device 100 as the measured values. The interval between each joining test is set to 60 [sec] as an example.

[0100] In addition, the number of repetitions of the joining test is determined based on the limit of the number of times the automotive brake pipe is removed during the period from when the vehicle is new to when it is scrapped. The automotive brake pipe does not have frequent opportunities to be removed, but its limit is estimated based on the discrete probability distribution with the number of times it is removed as a probability variable. Here, as the target components for joining the brake pipe, three elements, namely the ABS unit, the master cylinder, and the brake unit, are envisioned. When these three elements fail, the open-end nut will surely be reused. On this premise, considering the failure probability of these three elements, the number of joining parts of the brake pipe, the average value of the period from when the vehicle is new to when it is scrapped, and other parameters. Thus, it is presumed that the number of times the brake pipe is removed is 6 times or more than 6 times, which is a low probability that can be ignored. Therefore, the number of repetitions of the joining test is 5 times, which is less than 6 times.

[0101] (3) Axial force reduction rate

[0102] As a parameter for evaluating the axial force change by repeating the joining test on the same open-end nut, the following formula 2 defines the axial force reduction rate α [kN / time].

[0103] α = -(F n - F1) / (n - 1)……2

[0104] Here, F1 [kN] is the maximum axial force generated in the first joining test, that is, the initial axial force. F n [kN] is the maximum axial force generated in the nth (where 1 < n < 6) joining test, that is, the nth axial force. Among them, formula 2 is in the case where the (n - 1)th axial force generated in the (n - 1)th time is F n-1 , and when 0 < F n < F n-1The condition holds. Therefore, α>0.

[0105] As described above, in this test, the number of repetitions is set to n=5, which is less than 6 times. Therefore, the above formula 2 defining the axial force reduction rate α can be rewritten as the following formula 2′ when the fifth axial force is set to F5.

[0106] α=-(F5-F1) / 4………2′

[0107] 3. Test results and evaluation

[0108] The test results of the combined test carried out in the above manner are as follows Fig.13 shown.

[0109] (1) Evaluation criteria

[0110] Each sample was evaluated based on the following criteria a and b based on the mechanical properties of the open nut.

[0111] ·Base a: Initial axial force F1 exceeds 10.0 [kN] and is less than 14.0 [kN]

[0112] ·The standard b-axis force reduction rate α is less than 1.75 [kN / time]

[0113] Reference a specifies the range of the initial axial force F1. The upper limit of reference a is determined based on the upper limit of the follow-up torque. The upper limit of the follow-up torque is determined in consideration of the pipe strength and vehicle vibration, and is 1.0 [Nm] as an example. The follow-up torque is related to the axial force, and the axial force corresponding to the upper limit of the follow-up torque is uniquely determined. The axial force is 14.0 [kN] as an example. The trend of the follow-up torque is that it is the largest at the initial connection accompanied by the plastic deformation of the annular portion formed on the pipe, decreases from the time when the open nut is reused, and does not change much depending on the number of reuses. Therefore, the axial force is less than the upper limit of reference a, thereby ensuring that the follow-up torque is less than the upper limit when it is reused. On the other hand, the lower limit of reference a is set so that when the open nut is reused, even if the axial force is reduced, the required coupling force of the pipe can be ensured. The axial force is 10.0 [kN] as an example. Therefore, the axial force exceeds the lower limit of reference a, and the required coupling force of the pipe can be ensured even when it is reused.

[0114] The reference b specifies the upper limit of the axial force reduction rate α. As an example, the axial force reduction rate α is above 1.75 [kN / time]. In this case, when the open nut is used again with the same tightening torque as when it was first combined, it will often be lower than the lower limit of the axial force even if it is combined with an open nut. The lower limit of the axial force is set based on the lower limit of the binding force required by the brake pipe. By adapting to the reference b, even if the open nut is used again and is combined with the same tightening torque as when it was first combined, it can be avoided that it is lower than the lower limit of the axial force. As a result, when the open nut is used again, the binding force required by the brake pipe can be ensured. In addition, the axial force reduction rate α is as small as possible, provided that α>0 is the condition.

[0115] (2) Evaluation results

[0116] Evaluation results such as Fig.14 In this figure, the samples are arranged in order of the average joint plating thickness t from small to large, and qualified samples that meet both benchmarks a and b and unqualified samples that do not meet at least one of these benchmarks a and b are summarized. Fig.14 In the table, the case where the reference a or the reference b is suitable is represented by "y", and the case where the reference b is not suitable is represented by "n". In addition, the case where the reference a and the reference b are suitable is represented by "YES", and the case where the reference a and the reference b are not suitable is represented by "NO".

[0117] (3) Investigation

[0118] from Fig.14 It can be understood that the suitability of benchmark a and benchmark b has nothing to do with the difference in coating agents, but depends on the average joint plating thickness t. The trend is that as the average joint plating thickness t increases, the initial axial force F1 and the axial force reduction rate α will probably decrease. On the contrary, as the average joint plating thickness t decreases, the initial axial force F1 and the axial force reduction rate α will probably increase. It is determined that the average joint plating thickness t is too large, benchmark a is not suitable, and the average joint plating thickness t is too small, benchmark b is not suitable.

[0119] Upon a rough observation of qualified samples, the average plating thickness t of the joints of the qualified samples is in the range of 2.1 < t < 19.7. The smaller the initial axial force F1 is, the more capable it is of ensuring the required bonding force of the pipe while reducing the damage to the pipe. In addition, considering the mass production of open nuts, the plating thickness can be as small as possible, which is beneficial to the production cost. Here, not only mechanical properties, but also considering the damage to the pipe and the production cost of the open nut, as the upper limit value of the average plating thickness t of the joint, for example, it is preferably less than 16.0 [μm], more preferably less than 14.0 [μm], and even more preferably less than 12.0 [μm]. That is, for the average plating thickness t of the joint, 2.1 < t < 16.0 is preferred, 2.1 < t < 14.0 is more preferred, and 2.1 < t < 12.0 is even more preferred.

[0120] The present disclosure is not limited to the above-described various modes and can be implemented in various ways. In the above-described various modes, open nuts are used for metal brake pipes, but the objects of use of open nuts are not limited to brake pipes. For example, various metal pipes such as steam pipes can also be used as the objects of use. The open nuts 1A and 1B are merely examples of pipe joints used for joining metal pipes. The present disclosure only requires that the external diameter of the male thread is 9.53 to 14.0 [mm] and the internal diameter of the contact portion is 4.98 to 8.44 [mm], and it can also be applied to open nuts having a shape different from the illustrated shape.

[0121] As the zinc-based plating, in addition to zinc-nickel alloy plating, there are also zinc plating, zinc-iron alloy plating, etc. In order to satisfy the mechanical properties required for open nuts, the average plating thickness t of the joint within the above range is sufficient. Therefore, the type of zinc-based plating can be selected corresponding to the corrosion resistance performance required according to the use of the open nut.

[0122] The coating area R involved in each of the above-mentioned methods is set on the entire surface of the open nut, that is, it is set on all the surfaces of the threaded portion, the head and the contact portion and the inner circumferential surface of the open nut passed by the through hole. However, it is only an example that the coating area is set to the entire surface. For example, the coating area can also be set limited to the surface of the threaded portion and the surface of the contact portion. In this case, the inner circumferential surface of the open nut passed by the through hole and the surface of the head are excluded from the coating area. In addition, it is not limited to setting the coating area on all the surfaces of the threaded portion and the contact portion. For example, the coating area can also be set on a part of the surfaces of the threaded portion and the contact portion. In this case, as an example, the coating area can also be set on a part of the threaded portion surface preferably more than 40%, more preferably more than 60%, and more preferably more than 80%. In addition, the coating area can also be set on a part of the contact portion surface preferably more than 40%, more preferably more than 60%, and more preferably more than 80%. The surface of the threaded portion refers to the surface of the thread formation range that is actually engaged with the female thread or is scheduled to be engaged with the female thread. In addition, the surface of the contact portion refers to a contact surface that actually contacts the annular portion or is expected to contact the annular portion.

[0123] Inventions that can be determined according to the above-mentioned embodiments and their modifications are disclosed below. In addition, in order to facilitate understanding of the present disclosure, reference symbols or figure numbers used in the description of the above-mentioned embodiments are recorded in parentheses, but are not limited to the shapes or structures of the illustrated configurations.

[0124] The pipe joint disclosed in the present invention is a pipe joint (1A, 1B) which is mounted on the outer periphery of a metal pipe (BT). The metal pipe (BT) is provided with an annular portion (Rp, 16, 26) protruding outward in the pipe radial direction at the end. The pipe joint (1A, 1B) is connected to a target component (MC1, MC2) in a state of contact with the annular portion, so that the pipe can be connected to the target component. The pipe joint (1A, 1B) comprises: a threaded portion (12, 22) having a male screw The male thread (12a, 22a) is meshed with the female thread (12b, 22b) provided on the object part; the head (13, 23) is provided on one end side of the threaded part and inputs a tightening torque when combined; the contact part (14, 24) is provided on the other end side of the threaded part and is used to contact the annular part and push the annular part to the object part when combined with the object part; the zinc-based plating layer (P1, P2) is provided on the The threaded portion, the head portion and the contact portion; and a resin coating (18, 28) located on the outermost surface outside the zinc-based plating layer, including a polyethylene-based substance, a lubricant and solid particles, the threaded portion, the head portion and the contact portion respectively pass through through holes (10, 20), the through holes (10, 20) extending in a direction parallel to the direction of travel of the male thread during engagement, the male thread of the threaded portion having an outer diameter of 9.53 to 14.0 [mm], the head portion including a first plane (13a, 23a) facing in the opposite direction to the direction of travel and a second plane (13b, 23b) orthogonal to the first plane, the contact portion including a contact surface (14a, 24a) capable of contacting the annular portion and having an inner diameter of 4.98 to 8.44 [mm], in a cross section (CL1, CL2) including a center line (CL1, CL2) extending in the same direction as the through hole and orthogonal to the second plane of the head portion Fig.11A or Fig. 11B The number of threads (R i) When the number of [threads] is as described, the first thread tooth is defined as the 1st thread tooth (R1), the second thread tooth is defined as the 2nd thread tooth (R2), the third thread tooth is defined as the 3rd thread tooth (R3), and the 4th thread tooth is defined as the 4th thread tooth (R4). In the said cross-section, the 1st region (Ar1) set on the 1st plane of the said head, the 2nd region (Ar2) set on the 2nd plane of the said head, the 3rd region (Ar3) set on the rear side surface of the said 3rd thread tooth, the 4th region (Ar4) set on the rear side surface of the said 4th thread tooth, and the 5th region (Ar5) set on the contact surface of the said contact part are defined. And, when 5 calculated values are defined as X1, X2, X3, X4, X5 and 4 measured values are defined as T1, T2, T3, T4, when the value obtained by (X1 + X2 + X3 + X4 + X5 + T1 + T2 + T3 + T4) / 9 is defined as the joint average plating thickness t [μm], 2.1 < t < 19.7 holds. The 5 calculated values are obtained by calculating the arithmetic mean of the thicknesses of the zinc-based coating measured at 7 points arranged unidirectionally at 10 [μm] intervals in each of the 1st region to the 5th region for the 1st region to the 5th region respectively. The 4 measured values are obtained by measuring the thicknesses of the zinc-based coating at the bottom of the tooth (M1) between the 2nd thread tooth and the 3rd thread tooth, the top of the 3rd thread tooth (M2), the bottom of the tooth (M3) between the 3rd thread tooth and the 4th thread tooth, and the top of the 4th thread tooth (M4) in the said cross-section respectively.

[0125] According to this pipe joint, for the joint average plating thickness t related to the thickness of the zinc-based coating provided on the pipe joint, 2.1 < t < 19.7 holds. Therefore, in the case of repeated connection and disconnection, an initial axial force with a rotation torque less than the upper limit value can be obtained, and the reduction rate of the axial force can be suppressed to a low level.

[0126] In one aspect of the pipe joint of the present disclosure, in the case of repeating the connection test including the connection operation and the disconnection operation n times (where 1 < n < 6), the maximum axial force generated in the 1st connection test is defined as the initial axial force F1 [kN], and the maximum axial force generated in the nth connection test is defined as the nth axial force F n [kN], and taking - (F nWhen the value obtained by (-F1) / (n - 1) is defined as the axial force reduction rate α [kN / time], 0 < α < 1.75 holds. In the combination operation, a test component (TM) equivalent to the target component and a test pipe (T) having the same outer diameter as the pipe and a test ring portion (TR) equivalent to the ring portion are prepared, and they are combined with the test component with a specified tightening torque in a state of being in contact with the test ring portion. In the release operation, the combination of the test pipe is released by loosening the combination after the combination operation. According to this method, for the axial force reduction rate α, 0 < α < 1.75 holds, and it is possible to suppress the reduction of the axial force during re-use. Even when combined with the same tightening torque as during the first use, the desired binding force can be obtained during re-use.

[0127] In this method, it may also be that the pipe is a brake pipe used for automotive brake piping, and when the tightening torque is in the range of 12.0 to 22.0 [Nm], 10.0 < F1 < 14.0 holds. In this case, the upper limit value of the follow-up torque is not exceeded, and it is possible to prevent damage to the brake pipe while avoiding the occurrence of loosening of the pipe joint.

[0128] The pipe with a pipe joint disclosed in the present invention comprises: a metal pipe (BT) having an annular portion (Rp, 16, 26) protruding outward in the pipe radial direction at an end thereof, and a bent portion (Bp) at a position away from the annular portion; and a pipe joint (1A, 1B) which is assembled on the outer periphery of the pipe in a state where it is prevented from falling off by the annular portion and the bent portion, and is coupled to an object component in a state where it is in contact with the annular portion, thereby enabling the pipe to be coupled to the object component. The pipe joint comprises : a threaded portion (12, 22) having a male thread (12a, 22a) that meshes with a female thread (12b, 22b) provided on the object component; a head portion (13, 23) provided on one end side of the threaded portion and inputting a tightening torque when engaged; a contact portion (14, 24) provided on the other end side of the threaded portion and used to contact the annular portion and push the annular portion toward the object component when engaged with the object component; a zinc-based plating layer (P1, P2), which are provided on the threaded portion, the head portion and the contact portion; and a resin coating (18, 28), which is located on the outermost surface outside the zinc-based coating, and includes a polyethylene-based substance, a lubricant and solid particles. The threaded portion, the head portion and the contact portion respectively pass through through holes (10, 20), and the through holes (10, 20) extend in a direction parallel to the direction of travel of the male thread during engagement. The male thread of the threaded portion has a thickness of 9.53 to 1. The outer diameter of the head portion is 4.0 [mm], the head portion includes a first plane (13a, 23a) facing in the opposite direction to the traveling direction and a second plane (13b, 23b) perpendicular to the first plane, the contact portion includes a contact surface (14a, 24a) capable of contacting the annular portion, and has an inner diameter of 4.98 to 8.44 [mm], and a cross section (CL1, CL2) including a center line (CL1, CL2) extending in the same direction as the through hole and perpendicular to the second plane of the head portion Fig.11A or Fig. 11B In the cross section of the male thread, the number of threads (R i) In the case of the number of [specific content not provided], the first thread tooth is defined as the 1st thread tooth (R1), the second thread tooth is defined as the 2nd thread tooth (R2), the third thread tooth is defined as the 3rd thread tooth (R3), and the 4th thread tooth is defined as the 4th thread tooth (R4). In the cross-section, the 1st region (Ar1) set on the 1st plane of the head, the 2nd region (Ar2) set on the 2nd plane of the head, the 3rd region (Ar3) set on the rear side of the 3rd thread tooth, the 4th region (Ar4) set on the rear side of the 4th thread tooth, and the 5th region (Ar5) set on the contact surface of the contact part are defined. And, when 5 calculated values are defined as X1, X2, X3, X4, X5 and 4 measured values are defined as T1, T2, T3, T4, when the value obtained by (X1 + X2 + X3 + X4 + X5 + T1 + T2 + T3 + T4) / 9 is defined as the joint average plating thickness t [μm], 2.1 < t < 19.7 holds. Among them, the 5 calculated values are obtained by calculating the arithmetic mean of the thicknesses of the zinc-based coating measured at 7 points arranged unidirectionally at 10 [μm] intervals in each of the 1st region to the 5th region for the 1st region to the 5th region, and the 4 measured values are the thicknesses of the zinc-based coating measured at the bottom of the tooth (M1) between the 2nd thread tooth and the 3rd thread tooth, the top of the 3rd thread tooth (M2), the bottom of the tooth (M3) between the 3rd thread tooth and the 4th thread tooth, and the top of the 4th thread tooth (M4) in the cross-section respectively.

[0129] For the pipeline with this pipe joint, a pipeline with a pipe joint capable of ensuring the mechanical properties required for reuse can be provided.

[0130] In one mode of the pipeline with this pipe joint, it can also be that when the combination test including the combination operation and the disassembly operation is repeated n times (where 1 < n < 6), the maximum axial force generated in the 1st combination test is defined as the initial axial force F1 [kN], and the maximum axial force generated in the nth combination test is defined as the nth axial force F n [kN], and taking - (F nWhen the value obtained by ( -F1) / (n - 1) is defined as the axial force reduction rate α [kN / time], 0 < α < 1.75 holds. In the combination operation, a test component (TM) equivalent to the target component and a test pipe (T) having the same outer diameter as the pipe and a test annular portion (TR) equivalent to the annular portion are prepared, and they are combined with the test component with a prescribed tightening torque in a state of being in contact with the test annular portion. In the release operation, the combination of the test pipe is released by loosening the combination after the combination operation. According to this method, for the axial force reduction rate α, 0 < α < 1.75 holds, so it is possible to suppress the reduction of the axial force during reuse, and even when combined with the same tightening torque as in the first use, the desired bonding force can be obtained during reuse.

[0131] In this method, it may also be the case that the pipe is a brake pipe used for automotive brake piping. When the tightening torque is in the range of 12.0 to 22.0 [Nm], 10.0 < F1 < 14.0 holds. In this case, regarding the initial axial force F1, 10.0 < F1 < 14.0 holds, it is possible to ensure that the upper limit value of the follow-up torque is not exceeded, and it is possible to prevent the loosening of the pipe joint while avoiding damage to the pipe used for the brake piping.

[0132] Another pipe joint disclosed in the present invention is a pipe joint (1A, 1B) mounted on the outer periphery of a metal pipe (BT), wherein the metal pipe (BT) is provided with an annular portion (Rp, 16, 26) protruding radially outward at an end thereof, and the pipe joint (1A, 1B) is capable of coupling the pipe to an object component (MC1, MC2) by coupling the pipe joint (1A, 1B) to the object component in a state of contact with the annular portion, and the pipe joint (1A, 1B) comprises: a threaded portion (12, 22) having a male thread (1 2a, 22a), the male thread (12a, 22a) meshes with the female thread (12b, 22b) provided on the object part; a head (13, 23), which is provided on one end side of the threaded part and inputs a tightening torque when engaged; a contact part (14, 24), which is provided on the other end side of the threaded part and is used to contact the annular part while pushing the annular part to the object part when engaged with the object part; a zinc-based plating layer (P1, P2), which is provided on the threaded part, the head The male thread of the threaded portion has an outer diameter of 9.53 to 14.0 [mm], and the head has a direction parallel to the direction of travel of the male thread when the male thread is engaged. The first plane (13a, 23a) in the direction opposite to the traveling direction and the second plane (13b, 23b) perpendicular to the first plane, the contact portion includes a contact surface (14a, 24a) capable of contacting the annular portion and has an inner diameter of 4.98 to 8.44 [mm], and the range of the average plating thickness t of the joint is set to: on a cross section (CL1, CL2) including a center line (CL1, CL2) extending in the same direction as the through hole and perpendicular to the second plane of the head Fig.11A or Fig. 11B In the cross section of the male thread, the number of threads (R i) In the case of the number of [description missing], the first thread tooth is defined as the 1st thread tooth (R1), the second thread tooth is defined as the 2nd thread tooth (R2), the third thread tooth is defined as the 3rd thread tooth (R3), and the 4th thread tooth is defined as the 4th thread tooth (R4). In the cross-section, a 1st region (Ar1) set on the 1st plane of the head, a 2nd region (Ar2) set on the 2nd plane of the head, a 3rd region (Ar3) set on the rear side of the 3rd thread tooth, a 4th region (Ar4) set on the rear side of the 4th thread tooth, and a 5th region (Ar5) set on the contact surface of the contact portion are defined. And, when five calculated values are defined as X1, X2, X3, X4, X5 and four measured values are defined as T1, T2, T3, T4, when the value obtained by (X1 + X2 + X3 + X4 + X5 + T1 + T2 + T3 + T4) / 9 is defined as the joint average plating thickness t [μm], where the five calculated values are the arithmetic averages of the thicknesses of the zinc-based plating measured at seven points arranged unidirectionally at 10 [μm] intervals in each of the 1st region to the 5th region, and the four measured values are the thicknesses of the zinc-based plating measured at the root (M1) between the 2nd thread tooth and the 3rd thread tooth, the crest (M2) of the 3rd thread tooth, the root (M3) between the 3rd thread tooth and the 4th thread tooth, and the crest (M4) of the 4th thread tooth in the cross-section. And, in the case of repeating the joining test including the joining operation and the releasing operation n times (where 1 < n < 6), the maximum axial force generated in the 1st joining test is defined as the initial axial force F1 [kN], and the maximum axial force generated in the nth joining test is defined as the nth axial force F n [kN]. When the value obtained by -(F n - F1) / (n - 1) is defined as the axial force reduction rate α [kN / time], 10.0 < F1 < 14.0 and 0 < α < 1.75 hold. Wherein, in the joining operation, a test component (TM) equivalent to the target component and a test pipe (T) having the same outer diameter as the pipe and a test ring portion (TR) equivalent to the ring portion are prepared, and they are joined with the test component with a tightening torque in the range of 12.0 to 22.0 [Nm] in a state of being in contact with the test ring portion. In the releasing operation, the joining of the test pipe is released by loosening the joining after the joining operation.

[0133] According to this pipe joint, for the axial force reduction rate α, 0 < α < 1.75 holds. Therefore, it is possible to suppress the reduction of the axial force during re - use. Even when combined with the same tightening torque as during the first use, the desired binding force can be obtained during re - use. Also, regarding the initial axial force F1, 10.0 < F1 < 14.0 holds. Therefore, it is possible to ensure that the upper limit value of the follow - up torque is not exceeded, prevent damage to the pipes used in the brake piping, and prevent the loosening of the pipe joint from being induced while avoiding damage to the pipes.

[0134] In one mode of this pipe joint, the range of the average plating thickness t of the joint may also be 2.1 < t < 19.7. According to this mode, in the case of repeated combination and disassembly, it is possible to obtain an initial axial force with a follow - up torque less than the upper limit value, and the axial force reduction rate can be suppressed to a low level.

[0135] The plating thickness measurement method of the pipe joint of the present disclosure is a plating thickness measurement method suitable for a pipe joint that is assembled on the outer periphery of a metal pipe (BT), the metal pipe (BT) having a ring - shaped portion (Rp, 16, 26) protruding radially outward at the end. The pipe joint can bind the pipe to the target component by binding to the target component (MC1, MC2) in a state of contacting the ring - shaped portion and has been plated. The pipe joint includes: a threaded portion (12, 22) formed with male threads (12a, 22a) that mesh with female threads (12b, 22b) provided on the target component; a head (13, 23) provided on one end side of the threaded portion and to which a tightening torque is input during binding; a contact portion (14, 24) provided on the other end side of the threaded portion and used for pushing the ring - shaped portion against the target component while contacting the ring - shaped portion when binding to the target component; and a plating layer (P1, P2) provided on the threaded portion, the head, and the contact portion. The threaded portion, the head, and the contact portion respectively pass through through - holes (10, 20) that extend in a direction parallel to the advancing direction of the male threads during binding. The male threads of the threaded portion have an outer diameter of 9.53 to 14.0 [mm]. The head includes a first plane (13a, 23a) facing the direction opposite to the advancing direction and a second plane (13b, 23b) orthogonal to the first plane. The contact portion includes a contact surface (14a, 24a) that can contact the ring - shaped portion and has an inner diameter of 4.98 to 8.44 [mm], including: in a cross - section ([ Fig.11A Or Fig. 11B of the cross - section) that includes a center line (CL1, CL2) extending in the same direction as the through - hole and is orthogonal to the second plane of the head, counting from the head side, the thread teeth (R i), when the first thread tooth is defined as the first thread tooth (R1), the second thread tooth is defined as the second thread tooth (R2), the third thread tooth is defined as the third thread tooth (R3), and the fourth thread tooth is defined as the fourth thread tooth (R4), in the cross section, a first area (Ar1) is set on the first plane of the head, a second area (Ar2) is set on the second plane of the head, a third area (Ar3) is set on the rear side surface of the third thread tooth, a fourth area (Ar4) is set on the rear side surface of the fourth thread tooth, and a fifth area (Ar5) is set on the contact surface of the contact portion; and a step of obtaining, for each of the first area to the fifth area, calculating the area in the first area to the fifth area. The step of obtaining five calculated values ​​X1, X2, X3, X4, and X5 by taking the arithmetic average of the thickness of the plating measured at seven points arranged unidirectionally at intervals of 10 [μm] in each area of ​​the fifth area; the step of obtaining four measured values ​​T1, T2, T3, and T4 by measuring the thickness of the plating at the root (M1) between the second thread and the third thread, the top (M2) of the third thread, the root (M3) between the third thread and the fourth thread, and the top (M4) of the fourth thread, respectively; and the step of obtaining the calculated value based on the formula (X1+X2+X3+X4+X5+T1+T2+T3+T4) / 9 as the average plating thickness t [μm] of the joint.

[0136] According to this measurement method, the average plating thickness t of the joint can be obtained based on the measured values ​​of the plating thickness in multiple parts of the pipe joint. The plating thickness is not the same in each part of the pipe joint. However, its thickness affects the mechanical properties of the pipe joint such as axial force. As a parameter representing the plating thickness of the pipe joint, the average plating thickness t of the joint is used, thereby accurately evaluating the correlation between the plating thickness and the mechanical properties without being affected by the differences in the plating thickness in different places. For example, in the case of mass-producing plated pipe joints, by using the average plating thickness t of the joint to manage the plating thickness, the mechanical properties such as axial force of each pipe joint can be accurately estimated.

[0137] The zinc-based plating layer P1 or P2 in each of the above-mentioned embodiments is equivalent to an example of the plating layer disclosed above. The above-mentioned disclosure is irrelevant to the resin coating layer on the outer side of the plating layer. Therefore, the above-mentioned disclosure can also be applied to the pipe joint having the plating layer on the outermost surface.

[0138] The disclosure of Japanese Patent Application No. 2019-156189 filed on August 9, 2019 is incorporated herein by reference in its entirety.

[0139] All documents, patent applications, and technical specifications described in this specification are incorporated herein by reference to the same extent as if each document, patent application, or technical specification was specifically and individually indicated to be incorporated by reference.

Claims

1. A pipe joint, wherein: The pipe joint is mounted on the outer periphery of a metal pipe, the metal pipe is provided with an annular portion protruding outward in the pipe radial direction at the end, and the pipe joint is connected to the counterpart component in a state of contact with the annular portion, so that the pipe can be connected to the counterpart component, and the pipe joint comprises: a threaded portion formed with a male thread that meshes with a female thread provided on the counterpart component; a head portion, which is provided at one end side of the threaded portion and to which a tightening torque is input when engaged; a contact portion provided at the other end side of the threaded portion and used to contact the annular portion and press the annular portion against the object component when the threaded portion is coupled to the object component; A zinc coating provided on the threaded portion, the head portion and the contact portion; as well as The resin coating is located on the outermost surface of the zinc-based coating and includes a polyethylene-based substance, a lubricant, and solid particles. The threaded portion, the head portion, and the contact portion are respectively passed through through holes, and the through holes extend in a direction parallel to the advancing direction of the male thread during engagement. The male thread of the threaded portion has an outer diameter of 9.53 to 14.0 mm, The head includes a first plane facing in a direction opposite to the traveling direction and a second plane orthogonal to the first plane. The contact portion includes a contact surface capable of contacting the annular portion and has an inner diameter of 4.98 to 8.44 mm. In a cross section including a center line extending in the same direction as the through hole and orthogonal to the second plane of the head, when the number of thread teeth constituting the male thread is counted from the head side, the first thread tooth is defined as a first thread tooth, the second thread tooth is defined as a second thread tooth, the third thread tooth is defined as a third thread tooth, and the fourth thread tooth is defined as a fourth thread tooth, respectively. In the cross section, a first region set on the first plane of the head, a second region set on the second plane of the head, a third region set on the rear side surface of the third thread, a fourth region set on the rear side surface of the fourth thread, and a fifth region set on the contact surface of the contact portion are defined, and, When five calculated values are defined as X1, X2, X3, X4, X5 and four measured values are defined as T1, T2, T3, T4, when the value obtained by (X1 + X2 + X3 + X4 + X5 + T1 + T2 + T3 + T4) / 9 is defined as the joint average plating thickness t, 2.1μm < t < 19.7μm holds. Among them, the five calculated values are obtained by calculating the arithmetic mean of the thicknesses of the zinc-based coating measured at seven points arranged unidirectionally at 10μm intervals in each of the first region to the fifth region for the first region to the fifth region respectively, and the four measured values are the thicknesses of the zinc-based coating measured at the bottom of the tooth between the second thread tooth and the third thread tooth, the top of the third thread tooth, the bottom of the tooth between the third thread tooth and the fourth thread tooth, and the top of the fourth thread tooth in the cross section respectively.

2. The pipe joint according to claim 1, wherein: In the case of repeating the coupling test including the coupling operation and the decoupling operation n times, where 1 < n < 6, the maximum axial force generated by the first coupling test is defined as the initial axial force F1, the unit of F1 is kN, and the maximum axial force generated by the nth coupling test is defined as the nth axial force F n , F n whose unit is kN. The value obtained by -(F n - F1) / (n - 1) is defined as the axial force reduction rate α. When the unit of α is kN / time, 0 < α < 1.75 holds. In the coupling operation, a test component equivalent to the target component and a test pipe having the same outer diameter as the pipe and a test annular part equivalent to the annular part are prepared, and they are coupled with the test component at a prescribed tightening torque in a state of being in contact with the test annular part. In the decoupling operation, the coupling of the test pipe is released by loosening the coupling after the coupling operation.

3. The pipe joint according to claim 2, wherein: The pipe is a brake pipe used for automotive brake piping. When the tightening torque is in the range of 12.0 to 22.0 Nm, 10.0 < F1 < 14.0 holds.

4. A pipe with a pipe joint, wherein: Comprising: A metal pipe having an annular portion protruding outward in the pipe radial direction at an end portion and a bent portion provided at a position away from the annular portion; and A pipe joint that is assembled to the outer periphery of the pipe in a state of being prevented from falling off by the annular portion and the bent portion, and is combined with an object component in a state of being in contact with the annular portion, thereby enabling the pipe to be combined with the object component. The pipe joint comprises: A threaded portion formed with a male thread that meshes with a female thread provided on the object component; A head provided at one end side of the threaded portion and input with a tightening torque during combination; A contact portion provided at the other end side of the threaded portion for pushing the annular portion against the object component while being in contact with the annular portion when combining with the object component; A zinc-based coating provided on the threaded portion, the head, and the contact portion; And A resin coating located on the outermost surface outside the zinc-based coating, comprising a polyethylene-based substance, a lubricant, and solid particles. The threaded portion, the head, and the contact portion respectively pass through through holes that extend in a direction parallel to the advancing direction of the male thread during combination. The male thread of the threaded portion has an outer diameter of 9.53 to 14.0 mm. The head includes a first plane facing the direction opposite to the advancing direction and a second plane orthogonal to the first plane. The contact portion includes a contact surface capable of contacting the annular portion and has an inner diameter of 4.98 to 8.44 mm. In a cross section including a center line extending in the same direction as the through hole and orthogonal to the second plane of the head, when counting the number of thread teeth constituting the male thread from the head side, the first thread tooth is defined as the first thread tooth, the second thread tooth is defined as the second thread tooth, the third thread tooth is defined as the third thread tooth, and the fourth thread tooth is defined as the fourth thread tooth respectively. In the cross section, a first region defined on the first plane of the head, a second region defined on the second plane of the head, a third region defined on the rear side of the third thread tooth, a fourth region defined on the rear side of the fourth thread tooth, and a fifth region defined on the contact surface of the contact portion are defined. And, When five calculated values are defined as X1, X2, X3, X4, X5 and four measured values are defined as T1, T2, T3, T4, when the value obtained by (X1 + X2 + X3 + X4 + X5 + T1 + T2 + T3 + T4) / 9 is defined as the joint average plating thickness t, 2.1μm < t < 19.7μm holds. Among them, the five calculated values are obtained by calculating the arithmetic mean of the thicknesses of the zinc-based plating measured at seven points arranged unidirectionally at 10μm intervals in each of the first region to the fifth region for the first region to the fifth region respectively, and the four measured values are the thicknesses of the zinc-based plating measured at the root between the second thread tooth and the third thread tooth, the crest of the third thread tooth, the root between the third thread tooth and the fourth thread tooth, and the crest of the fourth thread tooth in the cross section respectively.

5. The pipeline with a pipe joint according to claim 4, wherein: In the case of repeating the coupling test including the coupling operation and the decoupling operation n times, where 1 < n < 6, the maximum axial force generated in the first coupling test is defined as the initial axial force F1, the unit of F1 is kN, and the maximum axial force generated in the nth coupling test is defined as the nth axial force F n , F n whose unit is kN. The value obtained by -(F n - F1) / (n - 1) is defined as the axial force reduction rate α. When the unit of α is kN / time, 0 < α < 1.75 holds. In the coupling operation, a test component equivalent to the target component and a test pipe having the same outer diameter as the pipe and a test annular part equivalent to the annular part are prepared, and they are coupled with the test component at a prescribed tightening torque in a state of being in contact with the test annular part. In the decoupling operation, the coupling of the test pipe is released by loosening the coupling after the coupling operation.

6. The pipeline with a pipe joint according to claim 5, wherein: The pipe is a brake pipe used for automotive brake piping. When the tightening torque is in the range of 12.0 to 22.0 Nm, 10.0 < F1 < 14.0 holds.

7. A pipe joint, mounted on the outer periphery of a metal pipe, wherein the metal pipe is provided with an annular portion protruding radially outward at an end thereof, wherein the pipe joint is capable of coupling the pipe to a counterpart component by coupling the pipe to the counterpart component while being in contact with the annular portion, the pipe joint comprising: a threaded portion formed with a male thread that meshes with a female thread provided on the counterpart component; a head portion, which is provided at one end side of the threaded portion and to which a tightening torque is input when engaged; A contact portion, which is provided on the other end side of the threaded portion and is used to press the annular portion against the target component while contacting the annular portion when combining with the target component; A zinc-based plating, which is provided on the threaded portion, the head, and the contact portion; And A resin coating, which is located on the outermost surface outside the zinc-based plating and includes a polyethylene-based substance, a lubricant, and solid particles, The threaded portion, the head, and the contact portion respectively pass through through-holes, and the through-holes extend along a direction parallel to the traveling direction of the male thread during combination, The male thread of the threaded portion has an outer diameter of 9.53 to 14.0 mm, The head includes a first plane facing the direction opposite to the traveling direction and a second plane orthogonal to the first plane, The contact portion includes a contact surface capable of contacting the annular portion and has an inner diameter of 4.98 to 8.44 mm, The range of the joint average plating thickness t is set to: In a cross section including a center line extending in the same direction as the through-hole and orthogonal to the second plane of the head, when counting the number of thread teeth forming the male thread from the head side, the first thread tooth is defined as the first thread tooth, the second thread tooth is defined as the second thread tooth, the third thread tooth is defined as the third thread tooth, and the fourth thread tooth is defined as the fourth thread tooth respectively. In the cross section, a first region defined on the first plane of the head, a second region defined on the second plane of the head, a third region defined on the rear side of the third thread tooth, a fourth region defined on the rear side of the fourth thread tooth, and a fifth region defined on the contact surface of the contact portion are defined. And, When five calculated values are defined as X1, X2, X3, X4, X5 and four measured values are defined as T1, T2, T3, T4, when the value obtained by (X1 + X2 + X3 + X4 + X5 + T1 + T2 + T3 + T4) / 9 is defined as the joint average plating thickness t, and the unit of t is μm. Among them, the five calculated values are obtained by calculating the arithmetic average of the thicknesses of the zinc-based coatings measured at seven points arranged unidirectionally at 10-μm intervals in each of the first region to the fifth region for the first region to the fifth region respectively. The four measured values are obtained by measuring the thicknesses of the zinc-based coatings at the root between the second thread tooth and the third thread tooth, the crest of the third thread tooth, the root between the third thread tooth and the fourth thread tooth, and the crest of the fourth thread tooth in the cross section respectively. And, In the case of repeating the coupling test including the coupling operation and the decoupling operation n times, where 1 < n < 6, the maximum axial force generated in the first coupling test is defined as the initial axial force F1, the unit of F1 is kN, and the maximum axial force generated in the nth coupling test is defined as the nth axial force F n , F n whose unit is kN. The value obtained by -(F n - F1) / (n - 1) is defined as the axial force reduction rate α. When the unit of α is kN / time, 10.0 < F1 < 14.0 and 0 < α < 1.75 hold, Among them, in the coupling operation, a test component equivalent to the target component and a test pipe having the same outer diameter as the pipe and a test annular portion equivalent to the annular portion are prepared, and they are coupled with the test component with a tightening torque in the range of 12.0 to 22.0 Nm in a state of being in contact with the test annular portion. In the release operation, after the coupling operation, the coupling is loosened to release the coupling of the test pipe.

Images