Tunnel excavator

Abstract

The tunnel excavator is provided with: a cutterhead; and a plurality of tool bits including a center bit disposed on the innermost circumferential side in the radial direction of the rotation center position. The center tool bit includes: a base material; and a first hard blade attached to the base material, the first hard blade including a first cutting and excavating surface that is a side surface extending in a direction parallel to the radial direction and that cuts or excavates at least one of underground sandy soil and an obstacle, the first hard blade including a first cutting and excavating surface that is a side surface extending in a direction parallel to the radial direction. When viewed from the tunneling direction side, the first cutting excavation surface of the first hard blade is disposed at a position offset from the rotation center position to the outside in the radial direction so as not to include the rotation center position of the cutterhead, and is disposed closest to the tunneling direction side.

Description

Technical Field

[0001] The present invention relates to a tunnel excavator having a cutter head. Background Art

[0002] Conventionally, a tunnel excavator having a cutter head has been known. This tunnel excavator is disclosed, for example, in Japanese Patent No. 6104617.

[0003] In Japanese Patent No. 6104617, a tunnel excavator having a cutter head is disclosed. This tunnel excavator includes a cutting head for sand, an obstacle cutting head, and a center cutting head. The cutter head is configured to rotate by driving of a drive motor and at the same time advance in the tunneling direction. The cutting head for sand, the obstacle cutting head, and the center cutting head are each configured to cut or excavate the sand and obstacles in front as the cutter head rotates and advances.

[0004] The center cutting head in Japanese Patent No. 6104617 is a cutting head disposed on the rotation center axis of the cutter head. The center cutting head includes a main body portion (base material) and a cemented carbide tip. When viewed from the tunneling direction side, the cemented carbide tips are arranged linearly along the radial direction of the rotation center axis so as to pass through the rotation center of the cutter head. The portion passing through the rotation center of the cemented carbide tip is the front end side portion on the tunneling direction side of the linear cemented carbide tip.

[0005] However, in the tunnel excavator of Japanese Patent No. 6104617, the cemented carbide tips of the center cutting head have a portion disposed at the position of the rotation center of the cutter head. The portion passing through the rotation center of the cemented carbide tip is the front end side portion on the tunneling direction side of the cemented carbide tip. Therefore, at the front end side portion passing through the rotation center of the cemented carbide tip, since the rotational speed (circumferential speed) of the cemented carbide tip accompanying the rotation of the cutter head is small (about 0), it is difficult to cut or excavate the sand and obstacles in front, and thus the cutting performance or excavation performance of the cemented carbide tips of the center cutting head is low. Therefore, it is desired to improve the cutting performance or excavation performance of the cemented carbide tips (hard cutting blades) of the center cutting head. Summary of the Invention

[0006] (I) Technical Problems to be Solved

[0007] The present invention has been made to solve the above problems, and an object of the present invention is to provide a tunnel excavator capable of improving the cutting performance or excavation performance of the cemented carbide tips based on the center cutting head.

[0008] (II) Technical Solution

[0009] To achieve the above objectives, the tunnel boring machine of the present invention comprises: a cutterhead that excavates as it rotates; and a plurality of cutter heads, including a central cutter head disposed on the excavation direction side of the cutterhead, wherein the central cutter head is arranged radially on the innermost circumferential side of the rotation center axis of the cutterhead, the central cutter head comprising: a base material; and a first hardened blade comprising a first cutting surface and mounted on the base material, wherein the first cutting surface is a side surface extending in a direction parallel to the radial direction and cutting or excavating at least one of underground sand and obstacles, and viewed from the excavation direction side, the first cutting surface of the first hardened blade is disposed at a position offset radially outward from the rotation center position, excluding the rotation center position of the cutterhead, and is disposed on the side closest to the excavation direction.

[0010] In the tunnel boring machine of the present invention, as described above, viewed from the tunneling direction side, the first cutting surface of the first hardened blade of the central cutter head is positioned radially outward from the rotation center position, excluding the rotation center position of the cutterhead, and is positioned closest to the tunneling direction side. Therefore, the first cutting surface of the first hardened blade positioned closest to the tunneling direction side, being positioned radially outward from the rotation center position excluding the rotation center position of the cutterhead, ensures that the rotational speed accompanying the rotation of the cutterhead is not approximately 0. As a result, even at the first cutting surface of the first hardened blade positioned closest to the tunneling direction side, cutting and excavating of sand and obstacles (such as steel) ahead can be performed. Therefore, compared to the case where the hardened blade of the central cutter head is positioned at the rotation center position of the cutterhead, the cutting or excavation performance based on the hardened blade of the central cutter head can be improved.

[0011] In a tunnel boring machine based on the above-described aspect, preferably, when viewed from the excavation direction side, the entire first hardened blade is arranged at a position excluding the rotation center of the cutterhead. If configured in this way, by arranging the entire first hardened blade at a position excluding the rotation center of the cutterhead, the rotational speed accompanying the rotation of the cutterhead within the entire first hardened blade can be made not to be approximately 0, thereby improving the cutting or digging performance based on the first hardened blade.

[0012] In a tunnel boring machine based on the above-mentioned aspect, preferably, when viewed from the tunneling direction side, the center cutter head is configured such that its center position is offset radially outward from the rotation center of the cutterhead. If configured in this way, it is easy to construct a center cutter head whose rotational speed accompanying the rotation of the cutterhead is not approximately zero simply by offsetting the center position of the center cutter head.

[0013] In a tunnel boring machine based on the above-mentioned aspect, preferably, the first hardened blade further includes a first front end face disposed on the digging direction side of the first cutting face, and the central cutter head further includes a second hardened blade, the second hardened blade including a second front end face disposed on the opposite direction side of the digging direction, closer to the first front end face. Viewed from the digging direction side, the second front end face of the second hardened blade is arranged to include the rotation center position of the cutterhead. If configured in this way, the second front end face of the second hardened blade can crush the sand and obstacles remaining on the rotation center position side of the cutterhead that were not cut by the first cutting face offset from the rotation center position, thus enabling the uncut sand and obstacles remaining in a crushed state to be transported rearward (in the opposite direction of the digging direction).

[0014] In this case, preferably, the base material of the central cutter head has a stepped shape, the stepped shape comprising: a first portion disposed on the digging direction side, which is a portion of a first cutting face on which a first hardened blade is mounted; and a second portion disposed on the side of the first portion opposite to the digging direction, which is a portion of a second front end face on which a second hardened blade is mounted. If configured in this way, simply by making the base material of the central cutter head stepped, it is possible to configure the second front end face of the second hardened blade in a manner that includes the rotation center position of the cutterhead, and to configure it on the opposite direction side of the digging direction than the first front end face. Therefore, it is easy to implement the configuration of the base material of the central cutter head with the second hardened blade.

[0015] In a tunnel boring machine having a central cutter head with a base material having the aforementioned stepped shape, preferably, the depth of the stepped shape of the base material of the central cutter head is less than half the length from the bottom surface to the first front end face of the first hardened blade in the digging direction. With this configuration, even when the base material is stepped, a portion of the first hardened blade extending from the bottom surface to the first front end face can be retained by the base material, thus reliably retaining the first hardened blade.

[0016] In a tunnel boring machine equipped with a central cutter head that also includes the aforementioned second hardened blade, preferably, when viewed from the digging direction side, the first front end face of the first hardened blade and the second front end face of the second hardened blade are arranged radially. With this configuration, in the circumferential direction of the cutterhead about its rotational axis, the first hardened blade can be held using the base material provided on both sides of the first front end face of the first hardened blade, and the second hardened blade can be held using the base material provided on both sides of the second front end face of the second hardened blade. Therefore, the first hardened blade and the second hardened blade can be held more reliably using the base material respectively.

[0017] In a tunnel boring machine equipped with a central cutter head having a base material with the aforementioned stepped shape, preferably, the first portion of the stepped base material includes a stepped surface disposed at the boundary with the second portion, and the central cutter head further includes a third hardened blade mounted on the stepped surface. With this configuration, the third hardened blade can protect the stepped surface from damage caused by sand and obstacles that come into contact with the stepped surface during the rotation of the cutterhead, thus suppressing damage to the stepped surface portion of the base material.

[0018] In this configuration, preferably, the third hardened blade includes a second cutting face, which is a side extending in a direction parallel to the radial direction and positioned on the opposite side of the digging direction than the first leading edge face of the first hardened blade. With this configuration, at least one of sand and obstacles can be cut or excavated via the second cutting face of the third hardened blade, thus further improving the cutting or digging performance of the hardened blade based on the center-head design.

[0019] In a tunnel boring machine based on the above-mentioned aspect, preferably, the first hardened cutting edge further includes a first front end face, which is disposed on the digging direction side of the first cutting face. The first front end face of the first hardened cutting edge has a flat surface extending in a direction orthogonal to the digging direction. With this configuration, because the first front end face has a flat surface, when the cutterhead moves along the digging direction, the load from sand and obstacles is not concentrated in one place at the front end portion of the first hardened cutting edge, thus suppressing damage to the front end portion of the first hardened cutting edge.

[0020] In a tunnel boring machine based on the above-mentioned aspect, preferably, the first hardened blade further includes: a first front end face disposed on the digging direction side of the first cutting face; and an inclined surface disposed on the radial outer periphery of the first front end face and inclined in the direction opposite to the digging direction. If configured in this way, the cuttings of at least one of the cut sand and obstacles can flow along the inclined surface, thus enabling the cuttings to flow effectively into the chamber within the cutterhead.

[0021] In a tunnel boring machine having a central cutter head with a base material having the aforementioned stepped shape, preferably, the first portion of the stepped base material includes a stepped surface disposed at the boundary with the second portion, and the first hardened blade also includes an inner circumferential parallel surface disposed on the stepped surface and extending parallel to the inner circumferential side of the first front end face in a direction opposite to the digging direction. With this configuration, the force in the digging direction of the first hardened blade, which moves with the cutterhead in the digging direction, can be concentrated at the front end portion of the first hardened blade, thus allowing the portion of the inner circumferential parallel surface exposed due to the stepped shape to easily bite into sand and obstacles. Attached Figure Description

[0022] Figure 1 This is a cross-sectional view of the tunnel excavator according to the first embodiment, shown from the side.

[0023] Figure 2 This is a front view of the cutterhead of a tunnel boring machine according to the first embodiment, viewed from the tunneling direction side.

[0024] Figure 3 This is a front view of the central part of the cutterhead of the tunnel boring machine according to the first embodiment, as viewed from the tunneling direction side.

[0025] Figure 4 This is a perspective view of the central cutter head of the tunnel excavator according to the first embodiment.

[0026] Figure 5 This is a front view of the center cutterhead of the cutterhead of the tunnel excavator of the first embodiment, viewed from the tunneling direction side.

[0027] Figure 6 It is along Figure 5 A sectional view along line VI-VI.

[0028] Figure 7 It is along Figure 5 A sectional view along line VII-VII.

[0029] Figure 8 This is a front view of the cutterhead of the tunnel excavator according to the first embodiment, viewed from the tunneling direction side, showing the area around the rotation center position of the cutterhead and the area around the center position of the central cutterhead.

[0030] Figure 9 This is a front view of the cutterhead of the tunnel boring machine according to the second embodiment, viewed from the tunneling direction side.

[0031] Figure 10 This is a perspective view of the central cutter head of the tunnel excavator according to the second embodiment.

[0032] Figure 11 This is a front view of the cutterhead of a tunnel boring machine, a variation of the first and second embodiments, as viewed from the tunneling direction side. Detailed Implementation

[0033] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0034] [First Implementation Method]

[0035] Reference Figures 1-7 The tunnel excavator 100 of the first embodiment will be described.

[0036] (Tunnel excavator)

[0037] In the figures, the X direction represents the direction parallel to the rotation center position Pc (rotation center axis) of the tunnel excavator 100, which extends along the excavation direction (front-to-back direction). The X1 direction represents the excavation direction (front) in the X direction, and the X2 direction represents the other direction (rear). Furthermore, the straight line extending along the X direction passing through the rotation center position Pc is the rotation center axis.

[0038] In each diagram, the Y-direction represents the left-right direction. Y1 represents the right side within the Y-direction, and Y2 represents the left side. In each diagram, the Z-direction represents the up-down direction. Z1 represents the top, and Z2 represents the bottom. In each diagram, the R-direction represents the radial direction of the tunnel excavator 100. R1 represents the radially outward direction, and R2 represents the radially inward direction. In each diagram, the θ-direction represents the circumferential direction of the tunnel excavator 100. θ1 represents one side of the circumferential direction, and θ2 represents the other side.

[0039] like Figure 1 As shown, the tunnel excavator 100 includes a cutterhead 1, multiple cutter heads 2, the excavator body 3, and a shield jack 4.

[0040] (Cutter head and cutter tip)

[0041] The cutterhead 1 is configured to advance as it rotates. For example... Figure 2 As shown, the cutter head 1 includes a central part 11, multiple cutter spokes 12, multiple secondary spokes 13, an intermediate ring 14, and an outer peripheral ring 15.

[0042] Multiple cutter spokes 12 extend radially from the central portion 11. Multiple secondary spokes 13 are arranged in the θ direction between adjacent cutter spokes 12. The multiple secondary spokes 13 are respectively mounted on an intermediate ring 14 and an outer ring 15. That is, the inner circumferential side (R2 direction side) of each of the multiple secondary spokes 13 is mounted on the intermediate ring 14. The outer circumferential side (R1 direction side) of each of the multiple secondary spokes 13 is mounted on the outer ring 15. Viewed from the tunneling direction side (X1 direction side), the intermediate ring 14 and the outer ring 15 are both circular. The intermediate ring 14 is arranged radially inside the outer ring 15 (R2 direction side).

[0043] like Figure 1As shown, the cutterhead 1 is configured to rotate in the θ direction around the rotation center position Pc (rotation center axis) via a drive motor (not shown). The cutterhead 1 is configured to excavate forward (in the X1 direction) via shield jacks 4. Multiple cutter heads 2 are disposed on the front surface (X1 direction side) of the cutterhead 1. The multiple cutter heads 2 are configured to cut or excavate at least one of the underground sand and obstacles as the cutterhead 1 rotates and excavates. The sand and obstacles cut by the multiple cutter heads 2 flow into the chamber 1a within the cutterhead 1 and are mixed with mud-making material in the chamber 1a. In this way, the strata are excavated using the multiple cutter heads 2.

[0044] In addition, the following text details the multiple cutting tool heads 2.

[0045] (Excavator body)

[0046] The excavator body 3 includes a main body 31, a central jack 32, a partition wall 33, a screw conveyor 34, and an installer 35. The main body 31 is a cylindrical component. A working space 31a is provided within the main body 31. The central jack 32 is located within the main body 31. The partition wall 33 is configured to divide the chamber 1a within the cutterhead 1 on the front side and the working space 31a within the main body 31. The screw conveyor 34 is configured to discharge sand and soil from the chamber 1a to the side of the working space 31a. The installer 35 is configured to form a ring that constitutes a section Seg of the tunnel wall.

[0047] (Shield tunneling jack)

[0048] The shield jack 4 forms a pressing section Seg, generating thrust. The tunnel excavator 100 advances forward using the reaction force of this pressing force.

[0049] (Detailed structure of the cutting tool tip)

[0050] like Figure 2 As shown, the cutting tool head 2 includes multiple obstacle cutting heads 21, multiple sand digging heads 22, and a center cutting head 23. The multiple obstacle cutting heads 21, multiple sand digging heads 22, and the center cutting head 23 are fixed to the front surface (X1 direction side) of the cutter head 1 by welding. Alternatively, the multiple obstacle cutting heads 21, multiple sand digging heads 22, and the center cutting head 23 may also be fixed to the front surface (X1 direction side) of the cutter head 1 by bolts instead of welding.

[0051] Multiple obstacle-cutting cutter heads 21 are arranged in the R direction. Multiple sand-digging cutter heads 22 are arranged in the R direction.

[0052] The device performs at least one of the following: cutting obstacles using multiple obstacle-cutting cutter heads 21 and excavating sand using multiple sand-excavating cutter heads 22. Furthermore, a switching mechanism (not shown) can switch between the state of cutting obstacles using multiple obstacle-cutting cutter heads 21 (obstacle-cutting state) and the state of excavating sand using multiple sand-excavating cutter heads 22 (sand-excavating state).

[0053] (Center cutter head)

[0054] The center cutter head 23 is the cutter head disposed on the innermost circumference side of the cutterhead 1 in the R direction of the cutterhead 2. The center cutter head 23 is located in the central part 11 of the cutterhead 1. The center cutter head 23 is disposed on the tunneling direction (X1 direction) side of the cutterhead 2. The center cutter head 23 is configured to initially perform at least one of obstacle cutting and sand excavation in the cutterhead 2 in the tunneling direction (X1 direction).

[0055] like Figure 3 and Figure 4 As shown, the central cutting head 23 includes a base material 231, a first hardened cutting edge 232, a second hardened cutting edge 233, and a third hardened cutting edge 234.

[0056] (parent material)

[0057] like Figure 4 As shown, the base material 231 is formed of a material that is more resilient than the first hardened cutting tool 232, the second hardened cutting tool 233, and the third hardened cutting tool 234. The base material 231 is formed, for example, of steel such as S45C. Viewed from the tunneling direction side (X1 direction side), the outer peripheral surface of the base material 231 is formed by a circumferential portion Sr1 with a central angle greater than 180 degrees and a straight portion Sr2 connecting the two ends of the circumferential portion Sr1. The base material 231 has a first portion 231a, a second portion 231b, a first recess 231c, a second recess 231d, and a third recess 231e.

[0058] The base material 231 has a stepped shape including a first portion 231a and a second portion 231b. The first portion 231a is disposed on the X1 direction side of the base material 231. The second portion 231b is disposed on the X2 direction side of the first portion 231a of the base material 231. In the stepped-shaped base material 231, the first portion 231a is a convex portion protruding from the second portion 231b toward the X1 direction side, and the second portion 231b is a recessed portion from the first portion 231a toward the X2 direction side.

[0059] The first portion 231a of the stepped base material 231 includes a stepped surface St1 disposed at the boundary portion with the second portion 231b. The stepped surface St1 extends along the X direction. The stepped surface St1 is a flat surface. The second portion 231b of the stepped base material 231 includes a stepped surface St2 on the X1 direction side. The stepped surface St2 extends along the R direction. The stepped surface St2 is a flat surface. Furthermore, the stepped surface St1 is an example of the "stepped surface" as defined in the claims.

[0060] The first part 231a has the cutting face 232a of the first hardened cutting tool 232 installed. The first part 231a also has the cutting face 234a of the third hardened cutting tool 234 installed. The second part 231b has the front end face 233a of the second hardened cutting tool 233 installed. The second part 231b also has the cutting face 234a of the third hardened cutting tool 234 installed.

[0061] The first recess 231c is recessed from the X1 direction side of the first portion 231a towards the X2 direction side. A first hardened cutting tool 232 is embedded in the recessed first recess 231c and is mounted thereon. The first portion 231a has an inclined surface SL1 as its X1 direction side surface. The inclined surface SL1 is inclined towards the X2 direction at the same angle as the inclined surface 232c of the first hardened cutting tool 232. The angle of inclination of the inclined surface SL1 is, for example, 25 degrees or more and 35 degrees or less. The inclined surface SL1 is inclined towards the X2 direction side from the end of the stepped surface St1 on the X1 direction side. The inclined surface SL1 is a curved surface that is more located in the X1 direction towards the inner circumference side.

[0062] The second recess 231d is recessed from the X1 direction side of the second portion 231b towards the X2 direction side. A second hardened cutting tool 233 is embedded in the recessed second recess 231d and is mounted thereon. The second portion 231b has an inclined surface SL2, which is the surface on the X1 direction side. The inclined surface SL2 is inclined towards the X2 direction at the same angle as the inclined surface 233b of the second hardened cutting tool 233. The angle of inclination of the inclined surface SL2 is, for example, 25 degrees or more and 35 degrees or less. The inclined surface SL2 is inclined towards the X2 direction side from the end of the stepped surface St2 on the R1 direction side. The inclined surface SL2 is a curved surface that is more located in the X1 direction towards the inner circumference side.

[0063] The third recess 231e is recessed into the X2 direction from the X1 direction side of the first part 231a and the X1 direction side of the second part 231b. A third hardened cutting tool 234 is embedded in the recessed third recess 231e. The second part 231b has an inclined surface SL3, which is the X1 direction side surface. The inclined surface SL3 is inclined in the X2 direction at the same angle as the inclined surface 234c of the third hardened cutting tool 234. The angle of inclination of the inclined surface SL3 is, for example, 25 degrees or more and 35 degrees or less. The inclined surface SL3 is inclined in the X2 direction from the R1 direction side end of the stepped surface St2. The inclined surface SL3 is a curved surface that is more inclined in the X1 direction towards the inner circumference.

[0064] like Figure 5 and Figure 6 As shown, the depth De of the stepped shape of the base material 231 of the central cutter head 23 is less than half of the length Lb of the first hardened cutting tool 232 in the X direction (digging direction) from the bottom surface of the first hardened cutting tool 232 to the front end face 232b (De < Lb / 2). The depth De of the stepped shape of the base material 231 of the central cutter head 23 is, for example, more than 15 mm and less than 25 mm.

[0065] (First Hardened Blade)

[0066] like Figure 5 and Figure 6 As shown, the first hardened cutting blade 232 is formed of a material harder than the base material 231. The first hardened cutting blade 232 is, for example, formed of a superhard alloy. The first hardened cutting blade 232 is configured to cut or excavate at least one of underground sand and obstacles. The first hardened cutting blade 232 has a cutting / excavating surface 232a, a front end surface 232b, an inclined surface 232c, and an inner peripheral parallel surface 232d. Furthermore, the cutting / excavating surface 232a is an example of the "first cutting / excavating surface" in the claims. Additionally, the front end surface 232b is an example of the "first front end surface" in the claims.

[0067] In the first embodiment, the cutting portion of the central cutter head 23, located on the X1 direction side, is positioned offset from the rotation center position Pc in the R1 direction. That is, the cutting surface 232a of the first hardened blade 232 is positioned offset from the rotation center position Pc in the R1 direction. Specifically, viewed from the digging direction (X1 direction) side, the cutting surface 232a of the first hardened blade 232 is positioned offset radially outward (R1 direction) from the rotation center position Pc, excluding the cutter head 1, and is located on the side closest to the digging direction (X1 direction) (see reference). Figure 7In summary, the first hardened cutting edge 232 is not positioned at the rotation center position Pc. Furthermore, viewed from the tunneling direction side (X1 direction side), the first hardened cutting edge 232 is positioned such that the rotation center position Pc, excluding the cutterhead 1, is not present. Additionally, the first hardened cutting edge 232 protrudes from the base material 231 in the X1 direction.

[0068] Viewed from the tunneling direction (X1 direction), this structure that offsets the cutting face 232a is achieved by offsetting the center position Pb (rotation center axis) of the center cutter head 23 from the rotation center position Pc of the cutterhead 1 towards the R1 direction. The center position Pb of the center cutter head 23 is not the center of gravity as viewed from the tunneling direction (X1 direction), but rather the center position in the R direction of the largest diameter portion of the center cutter head 23 as viewed from the tunneling direction (X1 direction). The straight line (rotation center axis) extending through the rotation center position Pc and along the X direction is parallel to the straight line extending through the center position Pb and along the X direction.

[0069] Here, as Figure 5 As shown, in the R direction, the front end of the cutting face 232a of the first hardened insert 232 in the R2 direction is offset from the rotation center position Pc of the cutter head 1 by an offset amount Gap. The offset amount Gap is, for example, more than 10 mm and less than 30 mm.

[0070] The cutting and excavating surfaces 232a are respectively provided in the θ1 and θ2 directions of the inner peripheral side parallel surface 232d. Each pair of cutting and excavating surfaces 232a is a side surface extending in a direction parallel to the R direction. The pair of cutting and excavating surfaces 232a are arranged at approximately the same staggered position in the R direction. An R-shaped chamfer is formed on the R2 direction side of each pair of cutting and excavating surfaces 232a.

[0071] The front face 232b is located on the side of the cutting face 232a in the excavation direction (X1 direction). The front face 232b has a flat surface extending along the R direction (see reference). Figure 7 An inclined surface 232c is provided on the radial outer periphery (R1 direction side) of the front end face 232b. The inclined surface 232c is inclined in the opposite direction of the tunneling direction (X2 direction). The inclination angle of the inclined surface 232c is, for example, more than 25 degrees and less than 35 degrees. An inner periphery parallel surface 232d is provided on the stepped surface St1. The inner periphery parallel surface 232d extends from the front end face 232b in the opposite direction of the tunneling direction (X2 direction). The inner periphery parallel surface 232d is the radial inner periphery (R1 direction side) portion.

[0072] (Second hardened blade)

[0073] like Figure 5As shown, the second hardened cutting tool 233 is formed of a material harder than the base material 231. The second hardened cutting tool 233 is, for example, formed of a superhard alloy. The second hardened cutting tool 233 is configured to cut or excavate at least one of underground sand and obstacles. The second hardened cutting tool 233 has a front end face 233a and an inclined face 233b. Furthermore, the front end face 233a is an example of the "second front end face" in the claims.

[0074] Viewed from the tunneling direction side (X1 direction side), the front end face 233a of the second hardened cutting tool 233 is arranged such that it includes the rotation center position Pc of the cutterhead 1. That is, the second hardened cutting tool 233 extends toward the R2 direction from the end of the base material 231 on the R1 direction side beyond the rotation center position Pc of the cutterhead 1.

[0075] In addition, such as Figure 6 As shown, the front end face 233a of the second hardened cutting tool 233 is positioned on the opposite side (X2 direction side) of the digging direction, further from the front end face 232b. The front end face 233a of the second hardened cutting tool 233 is positioned on the digging direction side (X1 direction side) further from the stepped surface St2. The front end face 233a of the second hardened cutting tool 233 is the face on the digging direction side (X1 direction side) of the second hardened cutting tool 233. The front end face 233a has a flat surface extending along the R direction (see reference). Figure 7 ).

[0076] An inclined surface 233b is provided on the radial outer periphery (R1 direction side) of the front end face 233a. The inclined surface 233b is inclined in the opposite direction to the tunneling direction (X2 direction). The inclination angle of the inclined surface 233b is, for example, more than 25 degrees and less than 35 degrees.

[0077] (Third hardened blade)

[0078] like Figure 5 As shown, the third hardened cutting tool 234 is formed of a material harder than the base material 231. The third hardened cutting tool 234 is, for example, formed of a superhard alloy. The third hardened cutting tool 234 is configured to cut or excavate at least one of underground sand and obstacles. The third hardened cutting tool 234 has a cutting and excavating surface 234a, a front end surface 234b, an inclined surface 234c, and an inner peripheral parallel surface 234d. Furthermore, the cutting and excavating surface 234a is an example of the "second cutting and excavating surface" of the claims.

[0079] The third hardened insert 234 is mounted across step surfaces St1 and St2. The third hardened insert 234 is mounted on the base material 231 across the first portion 231a and the second portion 231b.

[0080] The cutting surface 234a of the third hardened insert 234 is positioned offset from the rotation center position Pc in the R1 direction. Specifically, viewed from the digging direction (X1 direction) side, the cutting surface 234a of the third hardened insert 234 is positioned offset from the rotation center position Pc in the radially outward (R1 direction) direction, excluding the rotation center position Pc of the cutterhead 1.

[0081] The cutting and excavating surfaces 234a are respectively disposed in the θ1 and θ2 directions of the inner peripheral parallel surface 234d. A pair of cutting and excavating surfaces 234a are surfaces extending along a direction parallel to the R direction. The pair of cutting and excavating surfaces 234a are arranged at approximately the same staggered position in the R direction. For example... Figure 6 As shown, a pair of cutting surfaces 234a are positioned on the opposite side (X2 direction side) of the digging direction, further than the front end face 232b of the first hardened blade 232. The pair of cutting surfaces 234a includes at least the portion disposed in the digging direction (X1 direction) between the front end face 232b of the first hardened blade 232 and the front end face 233a of the second hardened blade 233. An R-shaped chamfer is formed on the R2 direction side of each pair of cutting surfaces 234a.

[0082] like Figure 7 As shown, the front end face 234b is provided on the digging direction (X1 direction) side of the cutting face 234a. The front end face 234b has a flat surface extending along the R direction. The inclined surface 234c is provided on the radial outer periphery side (R1 direction side) of the front end face 234b. The inclined surface 234c is inclined in the opposite direction (X2 direction) of the digging direction. The inclination angle of the inclined surface 234c is, for example, more than 25 degrees and less than 35 degrees. The inner periphery parallel surface 234d is provided on the step surface St1 and the step surface St2. The inner periphery parallel surface 234d extends from the front end face 234b in the opposite direction (X2 direction) of the digging direction. The inner periphery parallel surface 234d is the radial inner periphery side (R1 direction side).

[0083] (The relationship between the first, second, and third hardened cutting blades)

[0084] like Figure 8 As shown, viewed from the tunneling direction (X1 direction), the direction along the straight centerline C1 passing through the rotation center positions Pc and Pb is designated as direction A. Additionally, centerline C2 is a straight line extending along direction B, passing through the center position Pb. In the following explanation, the direction orthogonal to direction A is designated as direction B, viewed from the tunneling direction (X1 direction).

[0085] like Figure 8As shown, viewed from the tunneling direction (X1 direction), the first hardened cutting tool 232 and the second hardened cutting tool 233 are arranged radially (R direction). Furthermore, viewed from the tunneling direction (X1 direction), the front end face 232b of the first hardened cutting tool 232 and the front end face 233a of the second hardened cutting tool 233 are arranged radially (R direction). Additionally, a gap Ma is provided between the first hardened cutting tool 232 and the second hardened cutting tool 233, viewed from the tunneling direction (X1 direction), in the radial (R direction). The gap Ma is, for example, approximately 5 mm. Viewed from the tunneling direction (X1 direction), the third hardened cutting tool 234 is arranged between the first hardened cutting tool 232 and the second hardened cutting tool 233 in the θ2 direction. Furthermore, viewed from the tunneling direction (X1 direction), the first hardened cutting tool 232, the second hardened cutting tool 233, and the third hardened cutting tool 234 are arranged at equal angular intervals (approximately 90 degrees) in the θ direction.

[0086] The length Lr1 of the first hardened cutting tool 232 is longer than both the length Lr2 of the second hardened cutting tool 233 and the length Lr3 of the third hardened cutting tool 234. The length Lr2 of the second hardened cutting tool 233 is less than the length Lr1 of the first hardened cutting tool 232 and greater than the length Lr3 of the third hardened cutting tool 234. The length Lr3 of the third hardened cutting tool 234 is shorter than both the length Lr1 of the first hardened cutting tool 232 and the length Lr2 of the second hardened cutting tool 233.

[0087] The thickness Th1 of the first hardened cutting tool 232 is approximately the same as the thickness Th2 of the second hardened cutting tool 233 and the thickness Th3 of the third hardened cutting tool 234. In the B direction, the first hardened cutting tool 232, the second hardened cutting tool 233, and the third hardened cutting tool 234 each have a certain Th1, a certain thickness Th2, and a certain thickness Th3, respectively. The thicknesses of the first hardened cutting tool 232, the second hardened cutting tool 233, and the third hardened cutting tool 234 refer to their respective lengths in directions orthogonal to the X and R directions. The thicknesses Th1 of the first hardened cutting tool 232, Th2 of the second hardened cutting tool 233, and Th3 of the third hardened cutting tool 234 are all between 10 mm and 30 mm.

[0088] Viewed from the tunneling direction side (X1 direction side), the area of ​​the front end face 232b of the first hardened cutting edge 232 is approximately the same as the area of ​​the front end face 233a of the second hardened cutting edge 233. Viewed from the tunneling direction side (X1 direction side), the area of ​​the front end face 234b of the third hardened cutting edge 234 is smaller than both the area of ​​the front end face 232b of the first hardened cutting edge 232 and the area of ​​the front end face 233a of the second hardened cutting edge 233.

[0089] Viewed from the tunneling direction (X1 direction), the first hardened cutting edge 232 extends with the A direction as its long side. Viewed from the tunneling direction (X1 direction), the inner circumferential portion of the first hardened cutting edge 232 is formed into a rectangular shape with rounded corners. Viewed from the tunneling direction (X1 direction), the first hardened cutting edge 232 has a shape symmetrical with respect to the centerline C1.

[0090] Viewed from the tunneling direction (X1 direction), the second hardened cutting edge 233 extends with the A direction as its long side. Viewed from the tunneling direction, the inner circumferential portion of the second hardened cutting edge 233 is formed into a rectangular shape with rounded corners. Viewed from the tunneling direction, the second hardened cutting edge 233 has a shape symmetrical with respect to the centerline C1.

[0091] Viewed from the tunneling direction (X1 direction), the third hardened cutting tool 234 extends along the direction of the centerline C2, which is a straight line orthogonal to the centerline C1, i.e., direction B, as its long side. Viewed from the tunneling direction (X1 direction), the inner circumferential portion of the third hardened cutting tool 234 is formed into a rectangular shape with rounded corners. Viewed from the tunneling direction (X1 direction), the third hardened cutting tool 234 has a shape that is symmetrical with respect to the centerline C2.

[0092] Viewed from the tunneling direction (X1 direction), the first hardened cutting tool 232 and the second hardened cutting tool 233 are respectively positioned on one side and the other side of the A direction relative to the center position Pb. In the A direction, the overlap length La1 between the step surface St2 and the first hardened cutting tool 232 is smaller than the overlap length La2 between the step surface St2 and the second hardened cutting tool 233. Viewed from the tunneling direction (X1 direction), the third hardened cutting tool 234 is positioned only on one side along the centerline C2, i.e., the B direction, relative to the center position Pb.

[0093] Viewed from the tunneling direction (X1 direction), a straight section Sr2 forming the outer peripheral surface of the parent material 231 is arranged on the other side of the B direction, relative to the center position Pb. Viewed from the tunneling direction (X1 direction), the centerline C2 passes through the center position of the straight section Sr2 and is orthogonal to the straight section Sr2.

[0094] The step surface St1 is a surface extending in a direction orthogonal to the centerline C1. Viewed from the tunneling direction (X1 direction), the length Lst1 of the step surface St1 in the B direction on one side (the side where the third hardened cutting tool 234 is located) is smaller than the length Lst2 of the step surface St1 in the B direction on the other side of the B direction.

[0095] Viewed from the tunneling direction (X1 direction), a first hardened cutting tool 232 and a stepped surface St2 are disposed in the peripheral region Arb adjacent to the center position Pb. "The peripheral region Arb of the center position Pb" refers to the area near the center position Pb as viewed from the tunneling direction (X1 direction), and is adjacent to the center position Pb in a manner that surrounds it. Viewed from the tunneling direction (X1 direction), only a second hardened cutting tool 233 is disposed in the peripheral region Arc of the rotation center position Pc (rotation center axis). "The peripheral region Arc of the rotation center position Pc" refers to the area near the rotation center position Pc as viewed from the tunneling direction (X1 direction), and is adjacent to the rotation center position Pc in a manner that surrounds it.

[0096] (Effects of the first implementation method)

[0097] In the first embodiment, the following effects can be obtained.

[0098] In the first embodiment, as described above, when viewed from the tunneling direction (X1 direction) side, the cutting surface 232a of the first hardened blade 232 of the center cutter head 23 is positioned offset radially outward (R1 direction side) from the rotation center position Pc of the cutter head 1, and is positioned closest to the tunneling direction (X1 direction) side. Therefore, by positioning the cutting surface 232a of the first hardened blade 232 closest to the tunneling direction (X1 direction) side offset radially outward (R1 direction side) from the rotation center position Pc of the cutter head 1, the rotational speed of the cutting surface 232a of the first hardened blade 232 positioned closest to the tunneling direction (X1 direction) side is such that the rotational speed accompanying the rotation of the cutter head 1 is not approximately 0. As a result, even in the cutting and excavation face 232a of the first hardened blade 232 located on the side closest to the excavation direction (X1 direction), it is possible to cut and excavate the sand and obstacles (steel, etc.) in front. Therefore, compared with the case where the hardened blade of the center cutter head 23 is located at the rotation center position Pc of the cutter head 1, the cutting or excavation performance based on the hardened blade of the center cutter head 23 can be improved.

[0099] Furthermore, in the first embodiment, as described above, when viewed from the tunneling direction side (X1 direction side), the first hardened blade 232 is configured such that it excludes the rotation center position Pc of the cutterhead 1. Therefore, by configuring the first hardened blade 232 such that it excludes the rotation center position Pc of the cutterhead 1, the rotational speed accompanying the rotation of the cutterhead 1 is not approximately 0, thus improving the cutting or digging performance based on the first hardened blade 232.

[0100] Furthermore, in the first embodiment, as described above, when viewed from the tunneling direction (X1 direction), the center cutter head 23 is configured such that its center position Pb is offset from the rotation center position Pc of the cutterhead 1 to the radially outward side (R1 direction side). Thus, by simply offsetting the center position Pb of the center cutter head 23, it is easy to construct a center cutter head 23 whose rotational speed accompanying the rotation of the cutterhead 1 is not approximately 0.

[0101] Furthermore, in the first embodiment, as described above, the first hardened blade 232 includes a front end face 232b, which is disposed on the digging direction (X1 direction) side of the cutting face 232a. The center cutter head 23 includes a second hardened blade 233, which includes a front end face 233a, which is disposed on the opposite side of the digging direction (X1 direction) than the front end face 232b. Viewed from the digging direction (X1 direction) side, the front end face 233a of the second hardened blade 233 is disposed in a manner that includes the rotation center position Pc of the cutterhead 1. Thus, the front end face 233a of the second hardened blade 233 can be used to crush the sand and obstacles remaining on the rotation center position Pc side of the cutterhead 1 that have not been cut by the cutting face 232a which is offset from the rotation center position Pc.

[0102] Furthermore, in the first embodiment, as described above, the base material 231 of the central cutter head 23 has a stepped shape, which includes: a first portion 231a, which is located on the digging direction (X1 direction) side and has a cutting surface 232a of the first hard blade 232 mounted thereon; and a second portion 231b, which is located on the opposite side of the first portion 231a in the digging direction (X1 direction) and has a front end face 233a of the second hard blade 233 mounted thereon. Thus, by simply making the base material 231 of the central cutter head 23 into a stepped shape, it is possible to configure the front end face 233a of the second hard blade 233 in a manner that includes the rotation center position Pc of the cutter head 1, and to configure it on the opposite side of the digging direction (X1 direction) than the front end face 232b. Therefore, it is easy to realize the configuration of the base material 231 of the central cutter head 23 with the second hard blade 233 mounted thereon.

[0103] Furthermore, in the first embodiment, as described above, the depth De of the stepped shape of the base material 231 of the central cutter head 23 is less than half of the length Lb of the first hardened blade 232 from the bottom surface to the front end face 232b in the digging direction (X1 direction). Therefore, even when the base material 231 is stepped, the portion of the first hardened blade 232 from the bottom surface to the front end face 232b that is more than half the length Lb can be retained by the base material 231, thus reliably retaining the first hardened blade 232.

[0104] Furthermore, in the first embodiment, as described above, when viewed from the tunneling direction side (X1 direction side), the front end face 232b of the first hardened blade 232 and the front end face 233a of the second hardened blade 233 are arranged radially (R direction). Therefore, in the circumferential direction (θ direction) around the rotation center position Pc (rotation center axis) of the cutterhead 1, the first hardened blade 232 can be held using the base material 231 provided on both sides of the front end face 232b of the first hardened blade 232, and the second hardened blade 233 can be held using the base material 231 provided on both sides of the front end face 233a of the second hardened blade 233. Thus, the first hardened blade 232 and the second hardened blade 233 can be reliably held using the base material 231, respectively.

[0105] Furthermore, in the first embodiment, as described above, the first portion 231a of the stepped base material 231 includes a stepped surface St1 disposed at the boundary portion with the second portion 231b. The central cutter head 23 includes a third hardened blade 234 mounted on the stepped surface St1. Thus, the third hardened blade 234 can protect the stepped surface St1 from damage caused by sand and obstacles that come into contact with the stepped surface St1 during the rotation of the cutter head 1, thereby suppressing damage to the stepped surface St1 portion of the base material 231.

[0106] Furthermore, in the first embodiment, as described above, the third hardened blade 234 includes a cutting and digging surface 234a, which is a side surface extending in a direction parallel to the radial direction (R direction) and is positioned on the opposite side (X2 direction side) of the digging direction, further than the front end face 232b of the first hardened blade 232. Therefore, at least one of sand and obstacles can be cut or excavated using the cutting and digging surface 234a of the third hardened blade 234, thus further improving the cutting or digging performance of the hardened blade based on the central cutter head 23.

[0107] Furthermore, in the first embodiment, as described above, the first hardened cutting edge 232 includes a front end face 232b, which is disposed on the digging direction (X1 direction) side of the cutting and digging face 232a. The front end face 232b of the first hardened cutting edge 232 has a flat surface extending in a direction orthogonal to the digging direction (X1 direction). Therefore, because the front end face 232b has a flat surface, when the cutterhead 1 moves along the digging direction (X1 direction), the loads from sand and obstacles can be prevented from concentrating in one place at the front end portion of the first hardened cutting edge 232, thus suppressing damage to the front end portion of the first hardened cutting edge 232.

[0108] Furthermore, in the first embodiment, as described above, the first hardened cutting blade 232 includes: a front end face 232b disposed on the digging direction (X1 direction) side of the cutting and digging face 232a; and an inclined surface 232c disposed on the radial outer periphery side of the front end face 232b and inclined in the opposite direction to the digging direction (X1 direction). This allows the chips from at least one of the cut sand and obstacles to flow along the inclined surface 232c, thus enabling the chips to flow effectively into the chamber 1a within the cutterhead 1.

[0109] Furthermore, in the first embodiment, as described above, the first portion 231a of the stepped base material 231 includes a stepped surface St1 disposed at the boundary portion with the second portion 231b. The first hardened blade 232 includes an inner circumferential parallel surface 232d on its radially inner circumferential side, which is disposed on the stepped surface St1 and extends from the front end face 232b in the opposite direction to the digging direction (X1 direction). Thus, the force in the digging direction (X1 direction) of the first hardened blade 232, which moves with the cutterhead 1 in the digging direction (X1 direction), can be concentrated at the front end portion of the first hardened blade 232, thereby allowing the portion of the inner circumferential parallel surface 232d exposed due to the stepped shape to easily bite into sand and obstacles.

[0110] [Second Implementation]

[0111] Reference Figure 9 and Figure 10 The second embodiment will now be described. In this second embodiment, the central cutting head 230 includes a base material 230a, a first hardened blade 232, and a second hardened blade 233. That is, unlike the central cutting head 23 of the first embodiment, a third hardened blade 234 is not provided. Furthermore, in the figures, the same reference numerals are used to illustrate structures that are the same as those in the first embodiment.

[0112] (Tunnel excavator)

[0113] like Figure 9 As shown, the tunnel excavator 200 of the second embodiment includes a cutterhead 1, multiple cutter heads 2, and an excavator body 3 (see reference). Figure 1 ), and shield tunneling jack 4 (refer to Figure 1 ).

[0114] (Detailed structure of the cutting tool tip)

[0115] like Figure 9 As shown, the cutting tool head 202 includes multiple obstacle cutting heads 21, multiple sand digging heads 22, and a center cutting head 230.

[0116] (Center cutter head)

[0117] The center cutter head 230 is the cutter head in the tool head 202 that is arranged on the innermost circumference in the R direction of the cutter head 1.

[0118] like Figure 10 As shown, the central cutting head 230 includes a base material 230a, a first hardened cutting edge 232, and a second hardened cutting edge 233.

[0119] The base material 230a has a first portion 231a, a second portion 231b, a first recess 231c, and a second recess 231d. The base material 230a has a stepped shape including the first portion 231a and the second portion 231b.

[0120] In the second embodiment, the cutting surface 232a of the first hardened blade 232 is positioned offset from the rotation center position Pc in the R1 direction. Viewed from the tunneling direction side (X1 direction side), the front end face 233a of the second hardened blade 233 is positioned to include the rotation center position Pc of the cutterhead 1. Viewed from the tunneling direction (X1 direction) side, the first hardened blade 232 and the second hardened blade 233 are arranged radially (R direction).

[0121] The other structures of the second embodiment are the same as those of the first embodiment described above.

[0122] (Effects of the second implementation method)

[0123] In the second embodiment, the following effects can be obtained.

[0124] In the second embodiment, similarly to the first embodiment, when viewed from the tunneling direction (X1 direction) side, the cutting and digging surface 232a of the first hardened blade 232 is positioned offset radially outward (R1 direction side) from the rotation center position Pc of the cutterhead 1, and is located on the side closest to the tunneling direction (X1 direction). This improves the cutting or digging performance of the hardened blade based on the central cutter head 230.

[0125] The other effects of the second embodiment are the same as those of the first embodiment described above.

[0126] [Variation Example]

[0127] Furthermore, the embodiments and modifications disclosed herein should be considered illustrative in all respects and not restrictive. The scope of the invention is defined not by the description of the above embodiments but by the claims, and includes all modifications (variations) within the meaning and scope equivalent to the claims.

[0128] For example, the first and second embodiments described above illustrate the application of the invention to earth pressure tunnel boring machines (EPMs), but the invention is not limited thereto. The invention can also be applied to slurry tunnel boring machines.

[0129] Furthermore, in the first and second embodiments described above, an example is shown where, viewed from the tunneling direction side, the central cutter head 23 (230) is arranged such that its center position Pb is offset radially outward from the rotation center position Pc of the cutterhead 1; however, the present invention is not limited thereto. In the present invention, it is also possible to... Figure 11 As shown in the modified example, by making the radial length of the first hardened blade 3232 shorter than the length of the second hardened blade 3233, the cutting surface 3232a of the first hardened blade 3232 is positioned radially outward from the rotation center position Pc of the cutterhead 1 when viewed from the tunneling direction side. In this case, when viewed from the tunneling direction side (X1 direction side), the center position Pb of the central cutter head 323 is approximately the same as the rotation center position Pc of the cutterhead 1.

[0130] Furthermore, in the first and second embodiments described above, an example is shown where the central cutter head 23 (230) includes a second hardened blade 233, which includes a front end face 233a (second front end face) disposed on the opposite side of the digging direction than the front end face 232b (first front end face). However, the present invention is not limited thereto. In the present invention, the central cutter head may also not include the second hardened blade.

[0131] Furthermore, in the first and second embodiments described above, an example is shown where the depth De of the stepped shape of the base material 231 (230a) of the central cutter head 23 (230) is less than half the length Lb of the first hardened blade 232 in the digging direction; however, the present invention is not limited thereto. In the present invention, the depth of the stepped shape of the base material of the central cutter head may also be more than half the length of the first hardened blade in the digging direction.

[0132] Furthermore, in the first and second embodiments described above, examples are shown where the first hardened blade 232 and the second hardened blade 233 are arranged radially when viewed from the tunneling direction side; however, the present invention is not limited thereto. In the present invention, the first hardened blade and the second hardened blade may also be arranged at positions offset radially when viewed from the tunneling direction side.

[0133] Furthermore, in the first embodiment described above, an example is shown where the third hardened blade 234 has a cutting surface 234a in the tunneling direction; however, the present invention is not limited thereto. In the present invention, the third hardened blade may also not have a cutting surface.

Claims

1. A tunnel boring machine, characterized in that, have: The cutterhead, which digs as it rotates; and Multiple cutting tool heads, including a central cutting tool head, are disposed on the digging direction side of the cutterhead, wherein the central cutting tool head is arranged radially on the innermost circumference side of the rotational center axis of the cutterhead. The central cutting head includes: The base material; and A first hardened cutting blade, comprising a first cutting face, is mounted on the base material, wherein the first cutting face is a side extending in a direction parallel to the radial direction, and cuts or excavates at least one of underground sand and obstacles. Viewed from the tunneling direction side, the first cutting face of the first hardened blade is positioned offset radially outward from the rotation center position, excluding the rotation center position of the cutterhead, and is positioned closest to the tunneling direction side.

2. The tunnel excavator according to claim 1, characterized in that, Viewed from the tunneling direction side, the first hardened blade is configured such that it does not include the rotation center position of the cutterhead.

3. The tunnel excavator according to claim 1, characterized in that, Viewed from the tunneling direction side, the center cutter head is positioned such that its center position is offset from the rotation center position of the cutterhead to the radially outward side.

4. The tunnel excavator according to claim 1, characterized in that, The first hardened cutting tool further includes a first front end face, which is disposed on the digging direction side of the first cutting and excavating face. The central cutter head further includes a second hardened blade, the second hardened blade having a second front end face, the second front end face being disposed on the side opposite to the tunneling direction, further away from the first front end face. Viewed from the tunneling direction side, the second front end face of the second hardened blade is configured to include the rotation center position of the cutterhead.

5. The tunnel excavator according to claim 4, characterized in that, The base material of the central cutter head has a stepped shape, the stepped shape comprising: a first portion disposed on the side of the excavation direction, which is a portion of the first cutting excavation face on which the first hard blade is mounted; and a second portion disposed on the side of the first portion opposite to the excavation direction, which is a portion of the second front end face on which the second hard blade is mounted.

6. The tunnel excavator according to claim 5, characterized in that, The depth of the stepped shape of the base material of the central cutter head is less than half the length from the bottom surface of the first hard blade to the first front end face in the digging direction of the first hard blade.

7. The tunnel excavator according to claim 4, characterized in that, Viewed from the tunneling direction side, the first front end face of the first hardened blade and the second front end face of the second hardened blade are arranged radially.

8. The tunnel excavator according to claim 5, characterized in that, The first portion of the step-shaped base material includes a step surface disposed at the boundary portion with the second portion. The central cutting head also includes a third hardened cutting edge mounted on the stepped surface.

9. The tunnel excavator according to claim 8, characterized in that, The third hardened blade includes a second cutting face, which is a side surface extending in a direction parallel to the radial direction and positioned on the opposite side of the digging direction than the first front end face of the first hardened blade.

10. The tunnel excavator according to claim 1, characterized in that, The first hardened cutting tool further includes a first front end face, which is disposed on the digging direction side of the first cutting and excavating face. The first front end face of the first hardened cutting tool has a flat surface extending in a direction orthogonal to the digging direction.

11. The tunnel excavator according to claim 1, characterized in that, The first hardened blade also includes: A first front end face, which is disposed on the tunneling direction side of the first cutting and excavating face; and An inclined surface is disposed on the radial outer periphery of the first front end face and is inclined in a direction opposite to the tunneling direction.

12. The tunnel excavator according to claim 5, characterized in that, The first portion of the step-shaped base material includes a step surface disposed at the boundary portion with the second portion. The first hardened cutting tool also includes an inner circumferential parallel surface, which is disposed on the stepped surface and extends parallel to the inner circumferential side of the first front end face in a direction opposite to the tunneling direction.

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