JPH09287677A - Method and structure for fastening coupling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a fastening part between a coupling and a block in a compact manner, to provide excellent a fastening strength and excellent sealing ability for the fastening part, to reduce the number of fastening processes, and to simplify machining of a member for fastening. SOLUTION: A pipe coupling 1 is provided with a mounting part having a protrusion part, and a recessed part having a radial size larger than that of the protrusion part is formed in the opening end part of the flow passage of a block. A ring member 9 having approximately the same outside diameter as that of the recessed part and having approximately the same inside diameter as that of the protrusion part 3 of the mounting part of the pipe coupling 1 is arranged in the recessed part 5 of a block 2. The protrusion part 3 of the pipe coupling is inserted in the ring member and pressed thereagainst, and the pipe coupling 1 is fastened against the block 2 through plastic fluid deformation of the ring member 9. A vertical groove in a direction against torque and thrust and a peripherally continued peripheral groove for sealing are formed in the recessed part and the protrusion part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fastening method and a fastening structure for fastening a joint such as a pipe screw joint to an opening end of a flow path of a block, and in particular, the structure must be manufactured compactly, The present invention also relates to a joint fastening method and a fastening structure suitable for use in a fluid device that requires strong bonding and sealing properties.

[0002]

2. Description of the Related Art A conventional pipe threaded joint is shown in FIG. 13, for example. This joint is a pipe parallel thread joint 101 and has a PF screw (parallel thread) 1 as a mounting portion.
10 and the PF screw 110 is connected to the flow path 4 of the block 2.
It is fastened by screwing it into the screw portion 111 formed at the opening end of the. The PF screw 110 is screwed in by rotating the hexagonal nut portion 112 with a spanner.

A PF screw 7 similar to the PF screw 110 fixed to the block 2 side is provided on the upper portion of the hexagonal nut portion 112. The PF screw 7 is connected to a connecting member having a pipe thread of the same screw diameter, and has a tapered contact surface 8. The sealing property is maintained.

The O-ring 130 seals the block 2 and the pipe parallel thread joint 101. Therefore, the block 2 has a predetermined contact surface 131 as shown by A in the figure.
Has been processed.

The above is the case where the parallel threaded joint for pipes is taken as an example. However, there is also a taper screw joint for pipes having a taper screw as an attachment portion, and the taper screw joint for pipes is usually kept airtight by using a sealing tape.

Further, as a method of fastening and fixing the joint, there is a method of welding the block 2 and the joint. In this case, the joint is the hexagon nut 112 and PF screw 1 shown in FIG.
There may be only 10 and there may be a spigot connected to the flow path 4.

[0007]

Among the above-mentioned prior arts, the parallel threaded joint for pipes and the taper threaded joint are fixed to the block with screws, so that the threaded portion of the threaded portion is provided on the block 2 side in addition to the device mechanism portion as the fluid device. There is a problem in that the length of the wall thickness d2 is required and the size of the device becomes large. Also, when an O-ring is used for sealing, the number of man-hours for processing the fitting surface is large, and when a sealing tape is used,
There is a problem that chips of the sealing tape flow into the flow path as dust.

That is, since the parallel threaded joint for pipe 101 is fixed to the flow path opening end of the block 2 by the PF screw 110, the threaded portion 111 must be processed at the flow path opening end of the block 2, but the prepared hole Due to the existence of the screw portion 111 which is also combined, the device mechanism portion as the fluid device cannot be formed in the range indicated by d2 in the drawing.
The size of the block 2 must be increased only to secure the screw portion 111. Furthermore, since a spanner is used to fasten the PF screw 110, a sufficient space for rotating the spanner is required between the adjacent pipe screws, and the flow path interval must be set wider than necessary. .
Pipe taper screw joints have similar problems.

Further, in the pipe parallel thread joint 101, since the sealing is performed by the O-ring 130 as described above, it is necessary to process the shape of the contact surface 131 on the block 2. The contact surface roughness of the surface is usually about 6 μm in order to secure the sealing property without damaging the O-ring 130, and several steps such as taper processing are required, resulting in high processing cost.

In the taper threaded joint for pipes, the sealing tape used for maintaining airtightness may be cut into pieces by the thread when the screw is tightened and may be mixed in the flow path as dust. Therefore, it is rarely used in precision fluid equipment.

On the other hand, the method of welding the block and the joint does not have the problem of the above-mentioned pipe threaded joint. But,
There is a possibility that the block 2 is made of a material such as cast iron that is often used in fluid equipment and cannot be welded, or that cracks or fractures occur in a portion where high pressure is repeatedly applied. Furthermore, if there are many joints, it is very inefficient to weld one for each joint.

A first object of the present invention is to provide a joint fastening method and a fastening structure which can make the fastening portion between the joint and the block compact and which is excellent in fastening strength.

A second object of the present invention is to make the joint portion between the joint and the block compact, and to have excellent sealing property at the joint portion, and to simplify the man-hours for fastening and the processing of members for fastening. It is to provide a fastening method and a fastening structure of a possible joint.

[0014]

[Means for Solving the Problems]

(1) In order to achieve the above first object, the present invention employs the following configurations. That is, in the method of fastening a joint to fasten the joint to the flow path opening end of the block in which the flow channel is formed, a mounting portion having a convex portion is provided on the joint, and the flow path opening end portion of the block is formed from the convex portion. A concave portion having a large radial dimension is provided, and a ring member having substantially the same radial dimension on the outer side as that of the concave portion and having substantially the same radial dimension on the inner side as the convex portion is arranged in the concave portion, and the joint is attached to the ring member. The protrusion is inserted and pressed, and the ring member is plastically flow-deformed to fasten the joint to the flow path opening end of the block.

By fastening the joint and the block by the plastic flow deformation of the ring member in this way, the depth of the joint between the joint and the block may be the depth of the recess into which the ring member is inserted, and therefore the threaded portion. Also, the length of the joint is shorter than that of the prior art in which the prepared hole is provided, and the joint between the joint and the block is compact. In addition, because it is fastened by plastic flow deformation (metal flow) of the ring member,
It can be applied to members that cannot be welded, and a bond with excellent fastening strength can be obtained.

(2) Preferably, a groove is formed in a concave portion of the flow path opening end of the block and a convex portion of the fitting portion of the joint in a direction that resists torque and thrust acting on the joint, and the ring member. Pour into these grooves.

The ring member thus flowing into the groove resists the torque when tightening the pipe screw on the upper part of the joint and the thrust due to the pressure in the flow path and the like.

(3) In order to achieve the above-mentioned second object, the present invention provides a method for fastening a joint as described above, wherein a circumferential direction is provided in a concave portion of a flow path opening end of the block and an attaching portion of the joint. A continuous groove for sealing is formed in and the ring member is poured into these grooves.

The ring member flowing into the groove in this way acts as a seal, and fastening with excellent sealing property can be obtained without using an O-ring or a sealing tape that causes dust.

(4) Preferably, a groove is formed in the concave portion of the flow path opening end of the block and the convex portion of the joint mounting portion in a direction against the torque and thrust acting on the joint, and the block is formed. A groove for sealing which is continuous in the circumferential direction is formed in the concave portion of the flow path opening end and the fitting portion of the joint, and the ring member is poured into these grooves. As a result, both the actions (2) and (3) can be obtained.

(5) Further, preferably, the groove in the direction against the torque acting on the joint is provided on the side surface of the concave portion of the flow path opening end of the block and the convex portion of the fitting portion of the joint on the axial center of the joint. Is a vertical groove formed in parallel to the joint, and a groove in a direction against thrust acting on the joint is formed on the side surface of the concave portion of the flow path opening end of the block and the convex portion of the joint mounting portion. It is a lateral groove formed perpendicular to the axis.

The ring member that flows into the vertical groove resists the torque when tightening the pipe screw at the upper part of the joint, and the ring member that flows into the lateral groove resists the thrust due to the pressure in the flow path.

(6) The groove in the direction against the torque and thrust acting on the joint is provided on the side surface of the concave portion of the flow path opening end of the block and the convex portion of the joint mounting portion with respect to the axis of the joint. It may be a common diagonal groove formed with an angle. The function of the diagonal groove is the same as that of the vertical groove and the horizontal groove, and thus one type of groove can withstand both torque and thrust.

(7) Further, the groove in the direction against the torque and thrust acting on the joint is provided on the side surface of the concave portion of the flow path opening end of the block and the convex portion of the joint mounting portion with the axial center of the joint. It may be a common W groove formed in a zigzag shape at an angle with respect to. Also in this W groove, similarly to the above-mentioned diagonal groove, one type of groove can withstand both torque and thrust. Also, a stronger coupling to torque is obtained.

(8) Further, preferably, the circumferentially continuous sealing groove is formed on the bottom surface of the concave portion of the flow path opening end of the block and the base surface of the convex portion of the joint mounting portion. It is a circumferential groove.

The ring member flowing into the circumferential groove acts as a seal.

(9) The groove in the direction against the torque acting on the joint is parallel to the axis of the joint on the side surface of the concave portion of the flow path opening end of the block and the convex portion of the fitting portion of the joint. The formed vertical groove is a groove in a direction that resists thrust acting on the joint, and is formed on a side surface of the concave portion of the flow path opening end of the block and the convex portion of the fitting portion of the joint with respect to the axis of the joint. The groove may be a lateral groove formed vertically, and the lateral groove may be formed as a groove that is continuous in the circumferential direction with the depth of the groove being deeper than the depth of the vertical groove, and may also serve as the groove for sealing. .

As described in (5) above, the ring member that has flowed into the vertical groove resists the torque when tightening the pipe screw at the upper part of the joint, and the ring member that has flowed into the horizontal groove has thrust due to the pressure in the flow path. Against. Further, by making the depth of the lateral groove deeper than the depth of the vertical groove to form a continuous groove in the circumferential direction, the ring member that has flowed into a portion deeper than the vertical groove of the lateral groove acts as a seal.

(10) Further, in order to achieve the first object, the present invention adopts the following configuration. That is, in the fastening structure of the joint of the flow path opening end of the block forming the flow passage and the joint, the joint is provided with a mounting portion having a convex portion, and the flow passage opening end of the block has a radial dimension larger than that of the convex portion. A large concave portion is provided, and a ring member having substantially the same radial dimension on the outer side as that of the concave portion and having substantially the same radial dimension on the inner side as the convex portion is arranged in the concave portion. Is inserted, and the joint is fastened to the flow path opening end of the block by the plastic flow deformation of the ring member.

(11) Preferably, a groove is formed in the concave portion at the flow path opening end of the block and the convex portion of the joint mounting portion so as to resist the torque and thrust acting on the joint. (12) In order to achieve the second object, in the fastening structure of the joint, a groove for sealing that is continuous in the recessed portion of the flow path opening end of the block and the mounting portion of the joint in the circumferential direction. To form.

(13) Preferably, a groove is formed in the concave portion of the flow path opening end of the block and the convex portion of the joint mounting portion in a direction against the torque and thrust acting on the joint, and the block is formed. A groove for sealing which is continuous in the circumferential direction is formed in the concave portion of the flow path opening end and the mounting portion of the joint.

(14) The joint may be a pipe joint or a sealing plug.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 is a pipe joint for connecting a hydraulic pipe (not shown) to the flow path 4 of the block 2.
The block 2 is, for example, the housing of the control valve device. The pipe joint 1 has a convex portion 3 that constitutes an attachment portion on the fastening side of the block 2, and a concave portion 5 is provided at the opening end of the flow path 4 of the block 2. The diameter of the convex portion 3 of the pipe joint 1 is the same as the diameter of the flow channel 4, and the diameter of the concave portion 5 is slightly larger than the diameter of the flow channel 4 and the convex portion 3. On the convex portion 3 of the pipe joint 1, a ring retainer 6 forming another part of the mounting portion is provided, and on top of that, a PF screw portion 7 similar to the conventional one and a contact surface 8 for sealing the joint are provided. ing. A ring member 9 is arranged in the concave portion 5 of the block 2, and the convex portion 3 of the pipe joint 1 and the block 2 are firmly fastened by the plastic flow deformation (metal flow) of the ring member 9.

FIG. 2 shows a fastening step by plastic flow deformation of the ring member 9. As shown in FIG. 2A, block 2
The ring member 9 is inserted into the concave portion 5 of the pipe joint 1, the convex portion 3 of the pipe joint 1 is further inserted into the ring member 9, and the punch 10 is applied to the ring retainer 6 of the pipe joint 1 and pressed by the press. The ring member 9 has a diameter of the recess 5 of the block 2 as an outer diameter and a diameter of the protrusion 3 of the pipe joint 1 as an inner diameter, and has a ring shape having a height slightly larger than the depth of the recess 5. Use a softer material than 1. As an example, when the pipe joint 1 is an iron-based metal such as S45C and the block 2 is cast iron, the material of the ring member 9 is soft iron such as S20C, copper or its alloy, aluminum or the like.

Ring member 9 pressed by a press
Causes a flowable deformation as the pressing force increases, flows into grooves (described later) provided in the concave portion 5 and the convex portion 3, and a tightening force is generated between the block 2 and the pipe joint 1 to cause a pipe joint. 1 and the block 2 are firmly fastened.

FIG. 3 shows one of the grooves formed in the recess 5 of the block 2.
This is an example, and a vertical groove 21 parallel to the axis of the pipe joint 1 and a lateral groove 22 perpendicular to the axis of the pipe joint 1 are cut on the side surface 5a of the recess 5. The vertical groove 21 is a groove in a direction against the torque acting on the pipe joint 1, and the ring member 9 flowing into the vertical groove 21 prevents the ring member 9 (the pipe joint 1) from rotating when torque is generated. . The lateral groove 22 is a groove in a direction against the thrust acting on the pipe joint 1, and the ring member 9 flowing into the lateral groove 22 prevents the displacement due to the thrust when the ring member 9 (the pipe joint 1) is thrust. . The two grooves 21 and 22 are connected as shown in FIG. 4, and the upper end of the vertical groove 21 is open to the surface of the block 2. Further, it is difficult for the ring member 9 to completely flow into the bottom ends of the grooves 21 and 22, and a slight gap remains at the bottom ends of the vertical grooves 21. Therefore, the block 2 and the ring member 9 may not be completely sealed at the interface as they are. Therefore, a circumferential groove 23 continuous in the circumferential direction is cut on the bottom surface 5b of the recess 5 of the block 2 perpendicular to the axis of the pipe joint 1, and the circumferential groove 2
The ring member 9 that has flowed into 3 secures the sealing property.

FIG. 5 shows a groove 1 formed in the convex portion 3 of the pipe joint 1.
This is an example, and similar to the concave portion 5, the side surface 3a of the convex portion 3 has a vertical groove 31 parallel to the axial center of the pipe joint 1 and a lateral groove 32 perpendicular to the axial center of the pipe joint 1. The vertical groove 31 is a groove in a direction against the torque acting on the pipe joint 1, and the ring member 9 flowing into the vertical groove 31 prevents rotation of the pipe joint 1 when torque is generated. The lateral groove 32 is a groove in the direction against the thrust acting on the pipe joint 1, and the ring member 9 flowing into the lateral groove 32 prevents the displacement due to the thrust when the ring member 9 (the pipe joint 1) is thrust. . These two grooves 31 and 22 are also connected, and the vertical groove 3
1 has the upper end located near the surface of block 2,
As it is, the pipe joint 1 and the ring member 9 may not be completely sealed at the interface. Therefore, a circumferential groove 33 continuous in the circumferential direction is cut on the base surface (bottom surface of the ring retainer 11) 3b of the convex portion 3 of the pipe joint 1 which is perpendicular to the axis of the pipe joint 1, and this peripheral groove is formed. The ring member 9 flowing into 33 ensures the sealing property.

FIG. 6 shows a state in which the pipe joint 1 of the present embodiment is fastened to the block 2 in comparison with the conventional pipe joint (parallel pipe thread joint) 101. Since the conventional pipe joint 101 is fixed to the block 2 with a screw, the block 2 needs to have a wall thickness d2 corresponding to the length of the threaded portion and the prepared hole, which increases the size of the device. Further, as shown in FIG. 7, since the spanner 102 is used to perform the screw fastening, a space sufficient to rotate the spanner 102 is required between the adjacent pipe joints 101, and the flow path interval L2 Should be taken wider than necessary. On the other hand, in the pipe joint 1 of the present invention, since the ring member 9 is fastened by plastic flow deformation, the depth of the joint portion fitted into the block 2 is d.
It becomes 1 (<d2), which is much smaller than the conventional one. Further, since there is no need to use a spanner, no special space is required between the adjacent pipe joints 1, and the flow path interval L1
(<L2) can also be made small.

Since no O-ring is used for the seal,
Processing of the fitting surface of the O-ring is not required, member processing can be simplified, and since no sealing tape is used, there is no problem that chips from the sealing tape flow into the flow path as dust.

Furthermore, the pipe joint according to the present embodiment has the vertical groove 2
1, 31, the lateral grooves 22, 32, and the peripheral grooves 23, 33 are easy to process, and can be easily applied to cast iron such as FCD (spheroidal graphite cast iron) that cannot be welded, aluminum, and the like.

The above embodiment is an example given from the viewpoint of ease of processing, and the present invention is not limited to this and various modifications are possible. Several other embodiments of the present invention will be described below.

First, in the above-mentioned embodiment, the circumferential groove for sealing is cut on the bottom surface of the recess 5 of the block 2. However, in FIG. 8, the circumferential surface 5a of the recess 5 of the block 2 has a circular circumference so as not to be connected to the vertical groove 21. The circumferential groove 23A that is continuous in the direction may be cut, and the sealing performance can be ensured by the ring member 9 that also flows into the circumferential groove 23A. The same applies to the convex portion 3 side of the pipe joint 1.

Further, in the above embodiment, the vertical groove and the horizontal groove are separately cut as the grooves in the direction against the torque and thrust acting on the pipe joint 1, but as shown in FIG.
The common oblique groove 24 may be formed on the side surface 5a of the recess 5 at an angle with respect to the axis of the pipe joint. This diagonal groove 2
The action of No. 4 is the same as that of the vertical groove and the horizontal groove, and thus, one type of groove can withstand both torque and thrust. The same applies to the convex portion 3 side of the pipe joint 1.

Instead of the oblique groove 24, as shown in FIG. 10, common W grooves 25 and 36 may be cut in a zigzag shape at an angle with respect to the axis of the pipe joint 1. Also in this case, one type of groove can withstand both torque and thrust. Further, by forming the W groove, the component forces in the axial direction when torque acts on each other cancel each other out, and a stronger coupling with respect to torque is obtained. The same applies to the convex portion 3 side of the pipe joint 1.

Further, as the circumferential groove for sealing, an independent groove is formed in the above embodiment, but as shown in FIG. 11, a lateral groove (circumferential groove) 22A continuous in the circumferential direction is cut deeper than the vertical groove 21. The vertical groove 21 of the lateral groove 22A
The ring member that has flowed into a deeper portion acts as a seal and can secure the sealing property. The same applies to the convex portion 3 side of the pipe joint 1.

In the above embodiment, the pipe joint with the upper PF screw having the through hole is taken as the joint, but the present invention may be applied to a sealing plug having no PF screw and the through hole. FIG. 12 shows such an embodiment. In FIG. 12, the right side shows a conventional O-ring fit type sealing plug 101A, and the parallel threaded joint for pipe 10 shown in FIG. 13 is shown except that there is no upper PF screw and a through hole.
Same as 1. The left side of FIG. 12 shows the sealing plug 1A of the present embodiment. Like the pipe joint 1 with the upper PF screw shown in FIG. 1, a ring member 9A is arranged in the recess 5A of the block 2, and the ring member 9A is The plug 1A and the block 2 are fastened by plastic flow deformation (metal flow). No through hole is provided in the convex portion 3A of the plug 1A and the ring retainer 6A above it. Further, since it is a plug, no torque acts on it, so that lateral grooves 26, 27 for thrust supporting and sealing are cut on the side surface of the concave portion 5A and the lateral surface of the convex portion 3A.
The ring member 9A that has flowed into the shaft prevents the plug 1A from being displaced due to thrust and ensures the sealing performance.

Also in this embodiment, the same effect as when the present invention is applied to the pipe joint with the upper PF screw in the sealing plug is obtained.

[0049]

According to the present invention, since the joint between the joint and the block can be made compact, there is an effect of eliminating a wasteful space for fluid equipment and pipe parts using the joint.

Further, according to the present invention, the number of fastening steps and the processing of the members for fastening can be simplified, so that the working cost can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a joint portion between a pipe joint and a block showing a method for fastening a pipe joint according to an embodiment of the present invention.

FIG. 2 is a diagram showing a fastening process of a pipe joint.

FIG. 3 is an enlarged view of a flow path opening end portion of a block.

FIG. 4 is a development view of a side surface of a concave portion at a flow path opening end portion of a block.

FIG. 5 is an enlarged view of a mounting portion of a pipe joint.

FIG. 6 is a view showing a fastening state of a pipe joint according to an embodiment of the present invention in comparison with a conventional technique.

FIG. 7 is a view showing a state when a conventional pipe joint is fastened.

FIG. 8 is a development view of a side surface of a concave portion at a flow path opening end portion of a block according to another embodiment of the present invention.

FIG. 9 is a development view of a side surface of a concave portion at a flow path opening end portion of a block according to still another embodiment of the present invention.

FIG. 10 is a development view of a side surface of a concave portion at a flow path opening end portion of a block according to still another embodiment of the present invention.

FIG. 11 is an enlarged cross-sectional view of a recess at a flow path opening end of a block according to still another embodiment of the present invention.

FIG. 12 is a view showing a fastening state of a plug according to still another embodiment of the present invention in comparison with a conventional technique.

FIG. 13 is a view showing a shape of a recess at a flow path opening end of a conventional pipe joint and block.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pipe joint 2 Block 3 Convex part 3a Side surface 3b Base surface 4 Flow path 5 Recess 5a Side surface 5b Bottom surface 6 Ring retainer 7 PF screw 8 Contact surface 9 Ring member 21, 31 Vertical groove 22, 32; 22A Horizontal groove 23, 33 Circular groove 23A peripheral groove 24 diagonal groove 25 W groove 1A sealing plug 3A convex portion 5A concave portion 9A ring member 26, 27 lateral groove

Claims (14)

[Claims] 1. A method for fastening a joint to a flow path opening end of a block in which a flow path is formed, wherein a fitting portion having a projection is provided on the joint, and the flow path opening end of the block is provided with the mounting portion. A concave portion having a larger radial dimension than the convex portion is provided, and a ring member having substantially the same radial dimension on the outer side as the concave portion and substantially the same radial dimension on the inner side as the convex portion is arranged in the concave portion. A method for fastening a joint, characterized in that the convex portion of the attachment portion of the joint is inserted and pressed, and the ring member is subjected to plastic flow deformation to fasten the joint to the flow path opening end portion of the block. 2. A joint fastening method according to claim 1, wherein a groove at a flow path opening end portion of the block and a projection portion of the joint mounting portion are provided with a groove in a direction against torque and thrust acting on the joint. And a method of fastening the joint, wherein the ring member is poured into these grooves. 3. The joint fastening method according to claim 1, wherein a groove for sealing that is continuous in the circumferential direction is formed in the recess of the flow path opening end of the block and the mounting portion of the joint.
A method for fastening a joint, characterized in that the ring member is poured into these grooves. 4. The joint fastening method according to claim 1, wherein a groove at a flow path opening end of the block and a protrusion of an attachment portion of the joint are provided in a groove in a direction against torque and thrust acting on the joint. And forming a groove for continuous sealing in the concave portion of the flow path opening end of the block and the attachment portion of the joint in the circumferential direction, and allowing the ring member to flow into these grooves. How to fasten the joint. 5. The joint fastening method according to claim 2 or 4, wherein the groove in the direction in which the torque acting on the joint is resisted is a concave portion of the flow path opening end of the block and a convex portion of the joint mounting portion. Is a vertical groove formed parallel to the axis of the joint on the side surface of the joint, and the groove in the direction against the thrust acting on the joint is a concave portion of the flow path opening end of the block and the fitting portion of the joint. A method for fastening a joint, characterized in that it is a lateral groove formed on a side surface of the convex portion so as to be perpendicular to the axis of the joint. 6. The method of fastening a joint according to claim 2, wherein the groove in the direction against the torque and thrust acting on the joint has a concave portion at a flow path opening end of the block and an attachment portion of the joint. A joint fastening method, characterized in that a common diagonal groove is formed on the side surface of the convex portion at an angle to the axis of the joint. 7. The joint fastening method according to claim 2 or 4, wherein the groove in the direction against the torque and thrust acting on the joint is formed in the recess of the flow path opening end of the block and the fitting portion of the joint. A joint fastening method, characterized in that a common W groove is formed on the side surface of the convex portion in a zigzag shape at an angle with respect to the axis of the joint. 8. The method for fastening a joint according to claim 3, wherein the circumferential sealing groove is formed on the bottom surface of the recess at the flow path opening end of the block and at the joint mounting portion. A method for fastening a joint, characterized in that it is a circumferential groove formed on the base surface of the convex portion. 9. The joint fastening method according to claim 4, wherein the groove in the direction against the torque acting on the joint is a side surface of a concave portion of the flow path opening end of the block and a convex portion of the joint mounting portion. Is a vertical groove formed parallel to the axis of the joint, and the groove in the direction against the thrust acting on the joint is a concave portion of the flow path opening end of the block and a convex portion of the joint mounting portion. Is a lateral groove formed perpendicularly to the axis of the joint, the lateral groove having a groove depth deeper than the longitudinal groove depth and formed as a circumferentially continuous groove for sealing. A method for fastening a joint, which is also characterized in that it doubles as a groove. 10. A structure for fastening a joint of a flow path opening end of a block in which a flow passage is formed and a joint, wherein an attachment portion having a convex portion is provided on the joint, and a diameter of the block at the flow passage opening end is larger than that of the convex portion. A recess having a large directional dimension is provided, and a ring member having substantially the same radial dimension on the outside as the recess and having the same radial dimension on the inner side as that of the protrusion is arranged in the recess. The joint fastening structure characterized in that the joint is fastened to the flow path opening end of the block by the plastic flow deformation of the ring member. 11. The joint fastening structure according to claim 10, wherein a groove at a flow path opening end portion of the block and a projection portion of the joint mounting portion have a groove in a direction against torque and thrust acting on the joint. A joint fastening structure characterized by forming a joint. 12. The joint fastening structure according to claim 10, wherein a groove for sealing which is continuous in the circumferential direction is formed in the recess of the flow path opening end of the block and the fitting of the joint. Fastening structure for joints. 13. The joint fastening structure according to claim 10, wherein a groove at a flow path opening end of the block and a projection of an attachment portion of the joint are provided in a groove in a direction against torque and thrust acting on the joint. And a groove for sealing which is continuous in the circumferential direction in the concave portion of the flow path opening end of the block and the fitting portion of the joint. 14. The joint fastening structure according to claim 10, wherein the joint is either a pipe joint or a sealing plug.