JP2000120391A - Coupling structure of segment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly join a male coupling and a female coupling capable of facilitating the joining work of segments to each other and to enhance the assembling workability of the male coupling. SOLUTION: On the joining end surface on one side of a segment, a male coupling is provided, and on the joining end surface on the other side, a female coupling is provided. A bolt provided with a locking part consisting of a plain washer, a disk spring, and a head is erected on a base plate to be the male coupling. A clocking plate in which a cutout part for fitting a bolt is formed and which is insertedly engaged between the base plate and the locking part so as to be held by the elastic force of the disk spring is made the female coupling. A spacer making the gap between the base plate and the locking part a prescribed dimension is fitted to the bolt. The work piece W in which a flat metallic plate is forged in a cylindrical shape is made the spacer. A plurality of projected vertical stripes are formed on the inner circumferential surface of the spacer at intervals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joint structure of segments that form a cylindrical wall in the axial direction of a digging hole by mutually connecting a plurality of holes.

[0002]

2. Description of the Related Art As a method of constructing a tunnel, a so-called shield method is generally employed, in which a segment (mainly made of concrete or steel) is assembled on the inner surface side of an excavation hole to construct a cylindrical wall. As the segments used in the shield method, those having a rectangular shape in a plan view and an arc plate shape are mainly used, and these segments are joined together by bolts. When joining the segments by the bolts, a joint plate having holes communicating with each other when the joint surfaces of the segments are brought into contact with each other is buried in the vicinity of the joint surface of the segments. In general, a bolt is inserted into a hole of the above, and a nut is fastened and joined to the bolt. Further, there is also a structure in which an insert fitting as a nut member is embedded in each segment, and bolts penetrating adjacent segments are fastened to each other for joining.

However, in the above structure, a bolt is inserted into a hole of a joint plate at a construction site, and a nut is fastened to the bolt, or a bolt is fastened to an insert fitting embedded in each segment. Since work is required, there is a limit to shortening the assembly time.
It was difficult to adapt to automatic assembly by robots.
Furthermore, even if the secondary lining is omitted, it is necessary to close the bolt box formed in the segment in order to install the bolt and nut, and a new joint is aimed at speeding up the construction and saving labor. At present, the development of the structure was urgently needed.

[0004] Here, the present inventors have developed a segment that can be joined very easily and has a smooth inner surface. As shown in FIGS. 20 and 21, the segment 1 has a male joint 2 provided on one joint end surface 1a and a female joint 3 provided on the other joint end surface 1b. By joining the male joints 2, the joining end surfaces 1a and 1b of the segment 1 are joined to each other.

More specifically, the joining end surfaces 1a and 1b are brought into contact with each other in a state where a bolt 5 constituting the male joint 2 is inserted into a concave portion 4 formed on a side portion of the female joint 3. The segments 1 are slid with each other at the male joint 2
Is inserted into the notch 7 of the locking plate 6 constituting the female joint 3, and the head 8 of the bolt 5 is inserted into the back side of the locking plate 6, so that the male joint 2 and the female joint 3 are separated. The segments 1 are joined together, so that the segments 1 are joined together.

The bolt 5 of the male joint 2 is connected to the joint end face 1
a is fastened and fixed to a cap nut 12 welded and fixed to the back surface side of the base plate 11 embedded in a. Male joint 2
The base plate 11 and the locking plate 6 of the female joint 3 have side plates 13
Anchor bars 14 are welded and fixed via the joints, and the anchor bars 14 are integrated with the concrete forming the segment 1.

[0007] In the joint structure having the above structure, the bolt 5
A cylindrical spacer 15 formed to a predetermined length is attached to the head, and the spacer 15 secures a space between the head 8 and the base plate 11 to a predetermined size. In some cases, a flat washer is provided on the bolt 5 in order to smoothly enter the head 8 of the bolt 5 into the back side of the locking plate 6.

[0008]

By the way, as a spacer 15 for securing a space between the head 8 and the base plate 11 and for holding a washer, a cylindrical pipe cut into a predetermined length has been used. However, there are few bolts having a thickness just enough to the diameter of the bolt 5 and a sufficient thickness. In particular, in the case of a type in which a washer is held, if the diameter is too large with respect to the diameter of the bolt 5, the washer is inclined and the locking plate There was a problem that it was not locked well with No. 6. Moreover, there is a problem that a great deal of labor is required for the pipe cutting operation, and furthermore, even if the bolts 5 are inserted into the spacers 15 during assembly, the spacers 15 fall off from the bolts 5.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a problem in that it is formed to have a diameter exactly matching the diameter of a bolt to be inserted, has a sufficient thickness, and causes inclination of a washer and the like. It is another object of the present invention to provide a joint structure of a segment in which a spacer that is hard to fall off from the bolt when the bolt is inserted is attached to the bolt.

[0010]

In order to achieve the above object, a joint structure for a segment according to the first aspect of the present invention is provided by sliding the joint end surfaces of the segments.
It is a joint structure of a segment that joins these joining end surfaces, and one of the joining end surfaces has a base plate, a rod body erected on the base plate, and the rod provided at the tip of the rod body. A male joint consisting of a locking portion formed with a larger diameter than the body, and a cutout portion in which the rod body can be fitted from the side is formed on the other joint end surface, and the cutout portion has the cutout portion. A female joint consisting of a locking plate that locks the locking portion on the back side by being fitted between the locking portion of the rod and the base plate while slidingly fitting the rod body. A spacer formed in a cylindrical shape is fitted into the rod body, and a distance between the base plate and the locking portion is set to a predetermined size by the spacer. It is characterized by being forged. As described above, since the spacer that is attached to the rod and maintains the distance between the base plate and the locking portion is made into a cylindrical shape by forging a flat plate, the spacer that matches the diameter of the rod is used. Is done. This eliminates the inconvenience of being too large for the diameter of the rod. By properly selecting the thickness of the flat plate, a spacer having a sufficient thickness can be obtained.

[0011] The segment joint structure according to claim 2 is
2. The joint structure for a segment according to claim 1, wherein the height of the spacer is set to a predetermined size by press working after the spacer is forged into a cylindrical shape. That is, since the height of the spacer is formed to a predetermined size by press working, the height is set to the predetermined size with extremely high precision.

According to a third aspect of the present invention, there is provided a joint structure for a segment.
3. The joint structure for a segment according to claim 1, wherein a ridge projecting inward is formed on an inner peripheral surface of the spacer by the forging process so as to extend in a vertical direction. . As described above, the ridge is formed on the inner peripheral surface of the spacer by forging so as to extend in the vertical direction. When the spacer is mounted on the rod, the ridge of the spacer is securely locked by the rod. Is held.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing an embodiment of a segment joint structure according to the present invention. In FIG. 1, reference numeral 21 is a segment. This segment 21
Is an arc-shaped concrete segment formed in a rectangular shape in a plan view, and has a joining end face 2 in the circumferential direction of the excavation hole.
By joining the two together and joining the joint end faces 23 in the axial direction of the excavation hole, a cylindrical wall body composed of these segments 1 is constructed in the excavation hole.

As shown in FIG. 2, a plurality of male joints 2 are provided on one circumferential end face 22a of the segment 21.
4 are provided, and the other end face 22b in the circumferential direction is
As shown in FIG. 3, the same number of female joints 25 as the male joints 24 are provided.

As shown in FIGS. 4 and 5, the male joint 24 is located at a position where a base plate 27 having a hole 26 formed substantially at the center thereof communicates with the hole 26 on the back side of the base plate 27. A fixed cap nut 28, a pair of side plates 29 fixed on the back side of the base plate 27, and a screw portion 30 a which is inserted through the hole 26 from the front surface side of the base plate 27 and is inserted into the female screw portion of the cap nut 28 Bolt (rod) 3 fixed in a state protruding from base plate 27 by being fastened to 28a
The side plate 29 is provided with an anchor 31 for fixing the male joint 24 to the segment 21.

The bolt 30 is provided with a cylindrical spacer 32, a flat washer 33, and a plurality of disc springs (elastic members) 34 in order from the base plate 27 side. From the spring (34) and the head (large-diameter portion) 35 of the bolt 30, the locking plate 4
A locking portion 36 for locking to the lock 3 is formed. The distance between the flat washer 33 of the locking portion 36 having the above structure and the surface of the base plate 27 is set to a predetermined dimension h by the spacer 32.

The flat washer 33 forming the locking portion 36 is
The outer edge on the base plate 27 side is a circular arc-shaped curved surface. In other words, this flat washer 33
It is attached with the punching side at the time of the punching process facing the base plate 27. Flat washer 33 and head 35
Are disposed so that the taper directions thereof are opposite to each other.

Here, the outer edge portions of the respective disc springs 34 are arranged so as to be axially separated from each other. The female joint 25 has a locking plate 43 in which a notch 42 is formed, and a pair of side plates 44 is provided on the back side of the locking plate 43.
Are fixed, and a bottom plate 45 having an L-shaped cross section is provided between the side plates 44.

The side plate 44 is provided with an anchor 46 for fixing the female joint 25 to the segment 21. The notch 42 of the locking plate 43 of the female joint 25 is formed as a tapered surface 42b in which the vicinity of the end on the inner surface 42a gradually widens toward the end. A guide surface 47 is formed on the back surface 43b side of the locking plate 43 near the end of the notch 42.

As shown in FIGS. 6 and 7, the guide surface 47 has an end surface 43a of the locking plate 43 and a back surface 43 of the locking plate 43.
b, inner surface 42 of notch 42 in which tapered surface 42b is formed
a is formed in a curved concave shape, the dimension between the outermost edges of the guide surfaces 47 on the end face 43a side of the locking plate 43 is L1, and the male joint 24 is connected to the female joint 25. At the time of joining, the flat washer 33 disposed within the dimension L1 between the outermost edges is guided to the center X of the notch 42.

The thickness L2 of the locking plate 43 at the end of the guide surface 47 is determined by the locking portion 3 of the male joint 24.
6 is smaller than the dimension h between the flat washer 33 and the surface of the base plate 27. A recess 48 is formed in the joint end face 22 b provided with the female joint 25 on the side of the notch 42 of the locking plate 43 of the female joint 25.

Next, in the above joint structure, the spacer 3
2 is formed by performing the following processing steps. (1) First, as shown in FIG. 8, a predetermined thickness (about 2 to 3 m
m) The metal plate (flat plate) T is disposed between the lower die frame 51 for punching and the upper die frame 52, and the lower die frame 51 and the upper die frame 52 perform the punching process. A disk-shaped work W as shown in FIG. 9 is formed.

(2) Next, as shown in FIG. 10, the disc-shaped work W is disposed between the lower mold frame 53 for forging and the upper mold frame 54, and the lower mold frame 53 and the upper mold are arranged. Forging is performed by the frame 54 to form the work W into a bottomed cylindrical shape whose inner diameter is slightly larger than the outer diameter of the bolt 30 as shown in FIG. Note that, as shown in FIG.
A protrusion 53a is formed on the inner peripheral surface of the third mold 3, and a groove 54a is formed on the outer peripheral surface of the upper mold frame 54. As a result, when the work W is forged by the lower mold frame 53 and the upper mold frame 54, as shown in FIG. 13, the inner periphery of the cylindrical portion of the work W is formed by the groove 54a and the ridge 53a. A plurality of ridges 32a are formed on the surface in the vertical direction at intervals in the circumferential direction.

(3) Then, the cylindrical work W having the bottom is formed.
Is placed in a lower forging frame 55 as shown in FIG. 14, and the upper frame 56 is lowered from above. By doing so, the work W is further forged, and the bottom is punched out to form a cylindrical shape as shown in FIG. Here, in this forging process, the height of the cylindrical workpiece W is set to a dimension h + α slightly larger than the predetermined height h.

(4) Then, the work W is placed between the lower mold frame 57 and the upper mold frame 58 for pressing as shown in FIG. The dimension is reduced by the dimension α to obtain a predetermined dimension h.

By performing the above processes (1) to (4), a plurality of ridges 32a are formed on the inner peripheral surface of the flat metal plate T.
Are formed in the vertical direction and at intervals in the circumferential direction, and a spacer 32 having a predetermined height h is obtained.

According to the spacer 32 obtained by the above process, when the bolt 30 is inserted into the spacer 32 during assembly, the ridge 32a formed on the inner peripheral surface of the spacer 32 is locked to the bolt 30. By doing so, the spacer 32 is securely held by the bolt 30. This prevents the spacer 32 from dropping off from the bolt 30 during assembly, thereby making it possible to perform an assembling operation satisfactorily.

Next, the male joint 24 and the female joint 25 having the above structure are described.
Will be described. When joining the male joint 24 and the female joint 25 having the above structure, the female joint 25
The bolt 30 of the male joint 25 is inserted into the concave portion 48 formed on the side of the male joint 25.
So that the joint end face 22a of the segment 21 is disposed.
And the joining end face 22b are brought into contact with each other and are slid so that the notch 4 of the locking plate 43 forming the female joint 25 is formed.
2 is fitted with a bolt 30 constituting the male joint 24.

In this manner, the locking portion 3 of the bolt 30
The flat washer 33 constituting the guide plate 6 is a guide surface 47 of the locking plate 43.
, And is guided by the guide surface 47 so that the locking plate 4
3 enters the back side.

Here, the guide surface 47 of the locking plate 43 is
Since the flat washer 33 is disposed within the dimension L1 between the outermost edges of the guide surfaces 47, the flat washer 33 is formed by the guide surface 47 so that the notch 42 is formed. The bolt 30 of the male joint 24 is securely guided to the center X of the notch 42.
And the male joint 24 and the female joint 25 are accurately positioned.

Thereafter, when the flat washer 33 constituting the locking portion 36 enters the back side of the locking plate 43, the flat washer 33 is pushed up toward the head 35 of the bolt 30, and
The disc spring 34 disposed between the flat washer 33 and the head 35 is pressed. Then, the male joint 24 is drawn toward the female joint 25 together with the bolt 30, and the joint end faces 22a, 22b are brought into a state in which the joint end faces 22a, 22b are firmly pressed against each other as shown in FIGS. Joined.

Here, in the locking portion 36 of the male joint 24, the disc spring 34 has characteristics as shown in FIG. That is, as shown in the figure, the disc spring 34 has an area A where the change in the elastic force P is smaller than the change in the amount of deformation δ,
In the above-described joint structure, when the engaging plate 43 of the female joint 25 is engaged between the engaging portion 36 of the male joint 24 and the base plate 27, the disc spring 34 is set in the region A. , Bolt 3
The projection length of 0 and the thickness of the locking plate 43 are set.

As described above, according to the segment joint structure of the present embodiment, the locking plate 43 of the female joint 25 is provided.
By inserting the bolt 30 provided on the male joint 24 into the notch 42 formed at the bottom, the locking portion 36 of the bolt 30 can be very easily locked on the back side of the locking plate 43,
Bonding can be performed by the locking force.

Thus, the labor required for joining the segments 21 can be greatly reduced, as compared with the conventional fastening structure using bolts and nuts or the joining structure in which bolts are fastened to insert fittings.
The automatic assembly by the robot can be facilitated, and further, since there is no bolt box or the like, the work of closing the bolt box can be omitted.

The notch 4 of the locking plate 43 of the female joint 25
A curved concave guide surface 47 is formed on the back surface near 2 and the guide surface 47 guides the flat washer 33 of the bolt 30 of the male joint 24 to the back surface of the locking plate 43 while being guided. , The bolt 30 is positioned at the center X of the notch 42, so that the bolt 30 of the male joint 24 is
Is engaged with the notch 42 of the locking plate 43 of the female joint 25 so that the female joint 25 and the male joint 24 are drawn to each other in a state where they are accurately positioned, and the segments 21 are joined. The end faces 22a and 22b can be joined very firmly.

That is, when the male joint 24 and the female joint 25 are joined, even if the center position of the notch 42 of the locking plate 43 and the bolt 30 is shifted or the axis is slightly inclined, the locking plate 43 is The bolt 30 can be securely guided to the center X of the cutout portion 42 of the locking plate 43 without inconvenience of scraping, and the male joint 24 and the female joint 25 can be smoothly joined.

In addition, the locking portion 36 constituting the male joint 24
Has an elastic member in which a plurality of disc springs 34 are overlapped with each other, so that even if there is some dimensional error, the error can be tolerated. It is possible to construct a cylindrical wall having excellent earthquake resistance. Male joint 2
The locking plate 4 of the flat washer 33 constituting the locking portion 36 of FIG.
3 is formed as a curved surface 47 having an arc shape, so that the contact resistance between the locking portion 36 and the locking plate 43 at the time of joining can be greatly reduced. 36 can be guided very smoothly to the locking position on the back side of the locking plate 43.

Further, according to the joint structure of the segments described above, the metal plate T is formed into a disk shape and forged to form the spacer 32 formed in a cylindrical shape. A spacer 32 having a sufficient thickness corresponding to the diameter can be provided.
It is possible to prevent such a problem that the washer 33 is inclined and the locking plate 43 is scraped or the locking state with the locking plate 43 causes a trouble, without being too large with respect to the diameter of 0. .

Further, since a cutting operation requiring a great deal of labor can be omitted, the operation can be simplified. Further, since the height of the spacer 32 is formed to a predetermined dimension h by press working, the height dimension is extremely accurately adjusted to the predetermined dimension h as compared with the case where the spacer 32 is cut to the predetermined dimension h. Can be

Further, since a plurality of ridges 32a are formed on the inner peripheral surface of the spacer 32 so as to extend in the vertical direction at intervals in the circumferential direction, when the bolt 30 is inserted into the spacer 32 during assembly, The ridges 32a formed on the inner peripheral surface of the spacer 32 can be securely held by locking the ridges 32a of the spacer 32 to the bolts 30. Thereby, the spacer 3 at the time of assembly is
2 is prevented from falling off from the bolt 30, and the assembling work can be performed favorably.

In the above example, the bolt 30 is provided with the flat washer 33 and the disc spring 34. However, it is needless to say that the present invention can be applied to a structure in which the disc spring 34 is omitted. Also,
Both the flat washer 33 and the disc spring 34 may be omitted, and the head 35 of the bolt 30 may be brought into direct contact with the guide surface 47 of the locking plate 43 to be guided and joined. In addition, the segment 21 is not limited to being made of concrete, and may of course be made of steel. Further, in the above example, the female joint 25 is provided with the L-shaped bottom plate 45 to form a space for the head 35 of the bolt 30 of the male joint 24 to enter, but the bottom plate 45 is eliminated and the segment 21 is formed. A core or the like that forms a space for the head 35 may be attached to the mold.

[0042]

As described above, according to the segment joint structure of the present invention, the following effects can be obtained. According to the segment joint structure of the first aspect, since the spacer that is attached to the rod body and maintains the interval between the base plate and the locking portion is formed into a cylindrical shape by forging a flat plate, It is possible to provide a spacer suitable for the diameter of the rod. Thereby, the inconvenience that is too large for the diameter of the rod can be eliminated. By properly selecting the thickness of the flat plate, a spacer having a sufficient thickness can be obtained. Further, the pipe cutting operation requiring a great deal of labor can be omitted, so that the operation can be simplified.

According to the joint structure of the second aspect, since the height of the spacer is formed to a predetermined size by press working, the height of the spacer is higher than that in the case where the spacer is cut to the predetermined size. It is possible to provide a spacer having a predetermined dimension with extremely high precision.

According to the joint structure for a segment according to the third aspect, the ridge is formed on the inner peripheral surface of the spacer so as to extend in the up-down direction by forging. Can be reliably retained by being locked to the rod. Thereby, the spacer is prevented from falling off from the rod during the assembling, and the assembling work can be performed satisfactorily.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a joint portion of segments joined to each other for explaining a joint structure of a segment according to an embodiment of the present invention.

FIG. 2 is a perspective view of a joint end face provided with a male joint of a segment for explaining a joint structure of the segment according to the embodiment of the present invention.

FIG. 3 is a perspective view of a joint end face provided with a female joint of the segment for explaining a joint structure of the segment according to the embodiment of the present invention.

FIG. 4 is a perspective view of a female joint and a male joint for explaining a segment joint structure according to the embodiment of the present invention.

FIG. 5 is a cross-sectional view of a joint portion of a female joint and a male joint for explaining a joint structure of a segment according to the embodiment of the present invention.

FIG. 6 is a rear view of a part of a locking plate constituting the female joint for explaining the joint structure of the segment according to the embodiment of the present invention.

FIG. 7 is a front view of a part of a locking plate constituting the female joint for explaining the joint structure of the segment according to the embodiment of the present invention.

FIG. 8 is a cross-sectional view of a punching die for explaining a method of forming a spacer of a male joint constituting the joint structure of the segment according to the embodiment of the present invention.

FIG. 9 is a perspective view of a punched workpiece for explaining a method of forming a spacer of a male joint that constitutes a joint structure of a segment according to an embodiment of the present invention.

FIG. 10 is a cross-sectional view of a forging die for explaining a method of forming a spacer of a male joint constituting the joint structure of the segment according to the embodiment of the present invention.

FIG. 11 is a cross-sectional view of a forged workpiece for explaining a method of forming a spacer of a male joint constituting the joint structure of the segment according to the embodiment of the present invention.

FIG. 12 is a cross-sectional view of a forging die for explaining a method of forming a spacer of a male joint that constitutes the segment joint structure according to the embodiment of the present invention.

FIG. 13 is a cross-sectional view of a forged workpiece for explaining a method of forming a spacer of a male joint that forms a joint structure of a segment according to an embodiment of the present invention.

FIG. 14 is a cross-sectional view of a forging die for explaining a method of forming a spacer of a male joint constituting a joint structure of a segment according to an embodiment of the present invention.

FIG. 15 is a cross-sectional view of a forged workpiece for explaining a method of forming a spacer of a male joint constituting the joint structure of the segment according to the embodiment of the present invention.

FIG. 16 is a cross-sectional view of a press die for explaining a method of forming a spacer of a male joint that constitutes the segment joint structure according to the embodiment of the present invention.

FIG. 17 is a cross-sectional view of a joint portion of segments to be joined, illustrating a joint structure of the segment according to the embodiment of the present invention.

FIG. 18 is a cross-sectional view of a joint explaining a joint structure of segments according to the embodiment of the present invention.

FIG. 19 is a diagram illustrating a relationship between elasticity and bending of a disc spring provided in a male joint for explaining a joint structure of a segment according to an embodiment of the present invention.

FIG. 20 is a cross-sectional view of a joint portion of the segment, illustrating the configuration and structure of a male joint and a female joint provided in the segment.

FIG. 21 is a perspective view of a male joint and a female joint illustrating a configuration and a structure of a male joint and a female joint provided in a segment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Segment 22, 22a, 22b Joining end surface 24 Male joint 25 Female joint 27 Base plate 30 Bolt (rod) 32 Spacer 32a Ridge 36 Locking part 42 Notch 43 Locking plate h Predetermined dimension T Metal plate (flat plate)

Continued on the front page (72) Inventor Akihiko Nakano 2-3-3 Kandaji-cho, Chiyoda-ku, Tokyo Co., Ltd. Obayashi-gumi Tokyo head office (72) Inventor Hiroki Someya 1-12-1 Yurakucho, Chiyoda-ku, Tokyo Ishikawajima Building Materials Kogyo Kogyo Co., Ltd. (72) Inventor Okayama Shou Ishikawashima Building Materials Co., Ltd. 1-12-1 Yurakucho, Chiyoda-ku, Tokyo (72) Inventor Toshio Mochizuki 1040 Hoshiyama, Fujinomiya-shi, Shizuoka F-term (reference) 2D055 GC04 GC06

Claims (3)

[Claims] 1. A joint structure for a segment in which segments are joined to each other by sliding the joined end surfaces of the segments, wherein one joint end surface is provided with a base plate and an upright stand on the base plate. And a male joint consisting of a locking part formed at the tip of the rod and having a larger diameter than the rod, and the other end face of the rod has the male joint. A notch portion that can be fitted from the side is formed, and the rod is slid into the notch and fitted into the gap between the locking portion of the rod and the base plate, whereby the rod is inserted. A female joint comprising a locking plate for locking the locking portion to the back surface side, a cylindrical spacer is fitted into the rod, and the base plate and the locking portion are fitted by the spacer. And the spacer has a predetermined size, and the spacer is a flat plate. Joint structure of segments characterized by being forged into a cylindrical shape. 2. The joint structure for a segment according to claim 1, wherein the spacer has a predetermined height by press working after the spacer is forged into a cylindrical shape. 3. The spacer according to claim 1, wherein a ridge projecting inward is formed on an inner peripheral surface of the spacer by the forging process so as to extend in a vertical direction. Segment joint structure.