JPH1068292A - Cutter fitting mechanism and cutter holder for tunnel excavator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently allow an excavation both in hard ground and soft ground by making a roller cutter and a cutter bit fitted to a cutter disk mutually exchangeable from the inside on a tunnel excavator. SOLUTION: A cutter holder main body 4a is fixed to the cutter support frame 3 of a cutter disk. A rotary saddle 8 and a spacer 8b are fitted to angular shaft sections protruded on both sides of a roller cutter, the roller cutter is rotatably fitted with the engaging recess of the cutter holder main body 4a, and it is fixed by bolts 9a via a bearing cap 9. When the roller cutter is to be removed, the bolts 9a are loosened, a rotary saddle 8 is rotated by 180', and the roller cutter is extracted to the inside. A cutter bit 11 is inserted into the cutter holder main body 4a in combination with two support members 12, the support members 12 are separated to be locked on stoppers 6 of the cutter support frame 3, and their upper end edges are locked on the lock pieces 4b of the cutter holder main body 4a. The roller cutter and the cutter bit 11 can be exchanged from the inside in response to the excavated ground.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cutter mounting mechanism and a cutter holder for a tunnel excavator. In more detail, the roller cutter and the cutter bit can be exchanged with each other from the inside of the tunnel excavator, so that the same tunnel excavator can efficiently perform tunnel excavation on both hard ground and soft ground. And a cutter holder suitably used for the mechanism.

[0002]

2. Description of the Related Art In recent years, tunnel construction is often performed by mechanized construction using a tunnel excavator. In this case, it is necessary to excavate a wide range of ground from a hard rock layer to a soft ground layer including a crush zone.Therefore, a tunnel excavator having a cutter adapted for hard ground and a tunnel excavator having a cutter adapted for soft ground are respectively provided. Is being developed. Generally, a tunnel excavator for hard ground is provided with a roller cutter suitable for breaking rock, and a tunnel excavator for soft ground is provided with a cutter bit suitable for cutting ground. Generally, a cutter bit includes a block-shaped base portion and a blade portion (hereinafter referred to as a chip) protruding from an upper surface of the base portion, and a claw having a tip portion formed at an upper end side of the cutter portion. A mold cutter bit is used.

[0003] On the other hand, when a tunnel is excavated by a single excavator in the ground where there are many changes in the soil existing in both the soft ground and the hard ground, an all-geological adaptive tunnel excavation capable of adapting to all of these changing geology. Machines are also being developed. In this tunnel excavator, both a roller cutter and a cutter bit are almost uniformly arranged on a cutter disk provided on the front surface thereof, and a roller cutter works effectively on hard ground, and a cutter bit works effectively on soft ground. That is what I expected.

However, since the cutter disk of the all-geologically adaptive tunnel excavator is provided with a roller cutter and a cutter bit and their respective slip outlets (soil discharge outlets of the cutter portion), the structure becomes complicated and the diameter becomes small. Because the area of the cutter disk is small in the tunnel excavator of
In some cases, a space is taken by the cutter bit and its slip-out opening, and a predetermined roller cutter cannot be mounted.

Also, when excavating rock layers with a roller cutter, crushed rocks or gravel from the cutter bit discharge port cannot release the slip, so the cutter bit discharge port is closed and soil is removed. In the case where the soft soil layer is excavated with a cutter bit after changing the position, a complicated operation of opening the slip outlet is required.

Further, since the cutter bit is disposed so that the tip of the cutter bit is located slightly behind the tip of the roller cutter for excavating the bedrock layer, when excavating soft earth and sand with the cutter bit, A state in which the tip of the roller cutter is constantly pressed against the face with a strong force without rotating continues, and then a unidirectional pressing force is intermittently applied to the bearing portion inside the roller cutter for a long time. As a result, there is a problem that the bearing portion is adversely affected and uneven wear of the outer periphery of the roller cutter occurs.

On the other hand, a tunnel excavator for hard ground is disclosed in, for example, Japanese Patent Application Laid-Open No. Sho.
As disclosed in Japanese Patent No. 4317 or Japanese Unexamined Patent Publication No. 7-269292, when the roller cutter is worn out, the operator does not open the front of the excavator and goes out of the machine to replace the roller cutter. There has been proposed an excavator that can be replaced from the inside of the excavator.

However, there is no known device that can exchange the roller cutter and the cutter bit from the inside of the machine according to the hardness or softness of the ground to be excavated.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problem, and uses the roller cutter mounting portion of the conventional hard ground tunnel excavator as it is to connect the roller cutter to the inner side of the machine. The roller bit and the cutter bit can be installed inside the machine by configuring the cutter bit support member that can be inserted into the cutter holder after being removed to the cutter holder after attaching the cutter bit to the cutter holder. From each other as appropriate.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A cutter mounting mechanism according to the present invention comprises a box-shaped cutter holder formed on a cutter disc of a tunnel excavator, and a roller cutter bearing member mounted on an opposed inner wall surface of the cutter holder. And a pair of support members formed with a recess for supporting a base of the cutter bit, wherein the support members are provided inside the cutter holder from the cutter chamber side of the tunnel excavator. It is configured to be inserted into and engaged with.

A cutter mounting mechanism according to another aspect of the present invention includes a box-shaped cutter holder formed on a cutter disk of a tunnel excavator, and a roller cutter mounted on an opposing inner wall surface of the cutter holder. A bearing member, a cutter bit inserted between the roller cutter bearing members, and a pair of support members formed with a recess in which a base of the cutter bit is fitted. On each of the opposed inner wall surfaces, a locking portion for locking the support member is provided so as to oppose with a gap through which the support member can be inserted, and the support member is inserted into the cutter holder through the gap. It is configured such that after being inserted, it is moved to the locking portion side and locked.

Therefore, the cutter mounting mechanism of the present invention uses the cutter holder to which the roller cutter is mounted as it is, and the cutter bit is supported by the cutter holder where the roller cutter bearing member remains mounted after the roller cutter is removed. The roller cutter and the cutter bit can be easily exchanged by inserting and mounting the support member thus set in the cutter holder. The roller cutter bearing member is, for example, a rotary saddle and a bearing cap. In general, the cutter holder portion is formed between a pair of cutter support frames radially arranged on a cutter disk by using the cutter support frame, or directly by using the cutter support frame without using the cutter support frame. Some are located on the disk.

Further, since the roller cutter bearing member is kept housed in the cutter holder, no special care is required for its storage. In addition, by keeping the bearing member housed therein, intrusion of earth and sand can be prevented, so that cleaning work when re-attaching the roller cutter becomes unnecessary. In addition, since the work of attaching and detaching the bearing member is not required, the replacement work is also facilitated from this point.

In this cutter mounting mechanism, the cutter bit is formed such that the base has a thickness substantially equal to the distance between the opposed inner wall surfaces of the cutter holder in a state where the roller cutter bearing member is mounted. If so,
Since both the support member and the cutter bit are closely engaged and held in the cutter holder portion, it is not necessary to separately prepare a special member.

Since the base of the cutter bit is formed to have a size smaller than the outer diameter of the roller cutter in the in-plane direction of the roller cutter, a large sediment intake gap is formed between the base and the inner peripheral edge of the upper end of the cutter holder. In the formed one, discharge of excavated earth and sand becomes easy.

Further, in the above-mentioned cutter bit having a tip on two opposite sides and configured so that the tip can be positioned in two circumferential directions when mounted on a cutter disc, Since the width of the base can be made smaller than the outer diameter of the roller cutter, the clearance between the base and the upper edge of the cutter holder can be made large, and the excavation of the excavated earth and sand from the soft ground can be facilitated.

The cutter holder according to the present invention is a box-shaped cutter holder fitted and attached to a cutter disc of a tunnel excavator, comprising a pair of rotary saddles supporting both ends of a shaft of a roller cutter; It has a bearing cap for non-rotatably mounting the saddle in the cutter holder main body, and a pair of support members formed with a recess into which the cutter bit fits, and the support member is a tunnel excavator. It is configured to be detachably attached to the cutter holder body from the cutter chamber side.

Therefore, the cutter holder of the present invention can easily constitute a cutter mounting mechanism capable of exerting the above-described functions.

In this cutter holder, when the space between the opposing inner wall surfaces of the cutter holder portion is formed to have substantially the same dimension as the thickness of the base portion of the cutter bit to be inserted, both the support member and the cutter bit are used. Since it is closely engaged and held in the holder portion, it is not necessary to separately prepare a special member.

Further, a locking piece for locking the upper edge of the support member is formed near the upper end inside the cutter holder main body, and a gap is formed near the lower end of the cutter holder main body for inserting the support member. In the case of a cutter holder in which the width of the support member is formed to be substantially the same as the distance between the opposed inner wall surfaces of the cutter holder body, By inserting a cutter bit into the support member and inserting the cutter bit into the cutter holder, the support member is moved so as to be engaged with the locking piece of the cutter holder body, the opposed inner wall of the cutter holder body and the stopper. The cutter bit can be easily held in the cutter holder.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A cutter mounting mechanism and a cutter holder according to the present invention will be described below based on embodiments shown in the accompanying drawings. FIGS. 1A and 1B are diagrams showing an example of a tunnel excavator to which a cutter mounting mechanism of the present invention is applied, wherein FIG. 1A is a front view, FIG. 1B is a cross-sectional view taken along line II of FIG. FIG. 3 is a partially cutaway perspective view showing a roller cutter mounting state in one embodiment of the cutter mounting mechanism of the present invention. FIG. 3 is a drawing showing a cutter holder in the cutter mounting mechanism of FIG. 2, (a) is a front view, and (b) is a front view. ) Is a sectional view taken along the line BB of (a), (c) is a sectional view taken along the line CC of (b), FIG. 4 is a drawing showing the main body of the cutter holder of FIG. 3, and (a) is a transverse section. FIG. 5B is a cross-sectional view taken along the line IV-IV of FIG.
FIG. 6 is a sectional view taken along line V-V of FIG. 6A, and FIG.
FIG. 7 is a cross-sectional view for explaining in order of (b) and (c), FIG. 7 is a partially cutaway perspective view showing a cutter bit mounting state in the cutter mounting mechanism in FIG. 2, and FIG. 8 is a cutter holder in the cutter mounting mechanism in FIG. FIG. 9A is a front view, FIG. 9B is a sectional view taken along the line β-β in FIG. 7A, FIG. 9C is a sectional view taken along the line γ-γ in FIG. FIG. 10 is a cross-sectional view showing a frame portion of the holder, FIG. 10 is a cross-sectional view taken along the line XX of FIG. 8A, FIG. 11 is a drawing showing a cutter bit mounting procedure in the cutter mounting mechanism of FIG. FIG. 8A is a cross-sectional view corresponding to the cross section taken along line XX, and FIG.
FIG. 3 is a sectional view taken along line XI-XI of FIG. The roller cutter and the cutter bit in the above drawings are shown in FIG.
Except for (c), it is not particularly sectioned.

As shown in FIG. 1, a cutter support frame (hereinafter, simply referred to as a frame) 3 is provided on a cutter disk 2 provided on a front surface of a tunnel excavator (hereinafter, simply referred to as an excavator) 1. The frame 3 is made into a pair, and the cutter supporting frame 3 is placed between the two.
Is used to form the cutter holder 4. Also,
A cutter holder 40 that does not use the frame 3 is formed near the outer periphery of the cutter disk 2, and the configuration is the same as that of the cutter holder 4 between the frames 3. A roller cutter 5 for excavating hard ground is mounted on the illustrated cutter holder 4.

The cutter disk 2 is rotated about the center axis of the excavator 1 by a driving machine (not shown) provided in the body of the excavator 1.

FIG. 2 shows the cutter holder 4 using the frame 3 so that the cutter holder main body (hereinafter simply referred to as the main body) 4a is cut away to make the internal structure clear. The roller cutter 5 is mounted on the cutter holder 4. Although the main body 4a in the figure is formed separately from the frame 3 and the cutter disk 2, the main body 4a is not particularly limited to the separate body.
Alternatively, it may be formed integrally with the cutter disk 2.

Although the roller cutter 5 shown in FIG. 1 is provided with one roller portion 5a, the present invention is not particularly limited to one roller portion, and is shown in FIGS. Such a roller may be provided with two rollers, or may be provided with three or more rollers.

As is clear from FIG. 3 as well,
The main body 4a is a box-shaped member inserted between the two frames 3, and the bottom is open (see also FIG. 4A). On the periphery of the upper end surface of the main body 4 (a), a forehead-shaped engaging piece 4b is formed so that a later-described cutter bit support member 11 does not fall forward of the excavator 1. This locking piece 4b can be said to be one feature of the present invention. The main body 4a is mounted between the frames so as to be engaged with a stopper 6 protruding from each of the frames 3. FIG. 4 is a cross-sectional view showing the connection between the main body 4a and the frame 3.

On the other hand, the roller cutter 5 comprises a roller portion 5a and a rotating shaft (see FIG. 2) 5b penetrating the roller portion 5a. The roller 5a and the rotating shaft 5b
The details of the coupling mechanism are well known, and therefore are not shown. Square shaft portions 5c having a square cross section are formed at both ends of the rotating shaft 5b, and the square shaft portions 5c protrude from both sides of the roller portion 5a. A hexagonal seat 5d is formed at the base of one of the square shaft portions 5c so that a wrench can be engaged.

Engaging recesses 7 are formed in the opposing inner walls of the main body 4 a orthogonal to the frame 3. This engagement recess 7 is
A semicircular recess 7a in which a rotary saddle 8 to which the square shaft portion 5c of the roller cutter 5 is fitted rotatably engages, a rectangular recess 7b in which the bearing cap 9 engages, And a groove 7c through which the square shaft 5c passes. The bearing cap 9 is fixed to the main body 4a by bolts 9a so as to restrain the rotary saddle 8 from rotating with the semicircular recess 7a. Therefore,
If the bolt 9a is loosened, the rotary saddle 8 can rotate.
The rotary saddle 8 and the bearing cap 9 correspond to a roller cutter bearing member in the claims.

The rotary saddle 8 has a disk shape, and is provided with a square hole 8a into which the square shaft portion 5c of the roller cutter 5 is fitted. Further, a spacer 8b which is removably fitted to one side of the opening of the square hole 8a is bolted to the square shaft portion 5c fitted to the square hole 8a. When the square shaft portion 5c is fitted to the rotary saddle 8, the center axis of the roller cutter 5 does not coincide with the center axis of the rotary saddle 8, as shown in FIG. ing. This is for facilitating removal of the roller cutter 5 as described later.

In use, the L-shaped stopper plate 10 having a partially hexagonal recess 10a is provided on the hexagonal seat of the roller cutter 5 in order to fix the rotation shaft 5b while allowing only the roller portion 5a to rotate. Bolt 10b engaged with 5d
Is fixed to the main body 4a.

Thus, the roller cutter 5 is supported by the cutter holder 4.

The roller cutter 5 is connected to the cutter bit 1
In order to replace the roller cutter 1, it is necessary to disassemble the cutter holder 4 and extract the roller cutter 5 to the inside of the excavator 1 as follows.

That is, first, as shown in FIG. 6A, the stopper plate 10 is removed to the inside of the machine. Next, FIG.
As shown in FIG. 5, the bolt 9a is loosened to release the restraint of the rotary saddle 8 by the bearing cap 9, and the hexagonal seat 5 of the roller cutter 5 is tightened with a tool such as a wrench.
By rotating d by 180 ° (the rotary saddle 8 also rotates integrally), the position of the spacer 8b of the rotary saddle 8 is brought inside the machine. At this time, since the center axis of the roller cutter 5 and the center axis of the rotary saddle 8 were eccentric as described above,
Due to the 180 ° rotation, the roller cutter 5 moves slightly inward from the position before the rotation. As a result, a gap is generated between the roller cutter 5 and the face of the ground, and the roller cutter 5 can be easily removed.

Next, as shown in FIG. 6C, after removing the spacer 8b of the rotary saddle 8 from the square shaft portion 5c,
Alternatively, the roller cutter 5 is pulled out to the inside of the machine while the square shaft portion 5c is guided by the groove portion 7c of the main body 4a while being attached.

The procedure for removing the roller cutter is the same as that of the conventional one, but the following configuration is added so that the roller cutter 5 can be replaced with a cutter bit. FIG. 9 shows the inside of the cutter holder 4 after removing the stopper plate 10 and the roller cutter 5 as described above. The rotating saddle 8 is stored in the original place in the cutter holder 4 for storage together with the spacer 8b, and the bearing cap 9 is fixed in the original position by retightening the bolt 9a, and is excavated. Useful for preventing intrusion of earth and sand.

As shown in FIG. 7 and FIG. 8, first, two U-shaped support members 12 for supporting the cutter bit 11 are prepared. The support member 12 has a recess 12a into which the base 11a of the cutter bit fits.
Are formed. The base 11a of the cutter bit has a block shape, the width thereof is substantially the same as the width of the recess 12a of the support member 12, and the thickness thereof is substantially the same as the dimension between the opposed inner wall surfaces of the main body 4a. .

Then, as shown in FIG. 11, the base portion 11a of the cutter bit is inserted into the recess 12a in a state where the two support members 12 are overlapped, and the two support members 12 are attached to the cutter bit base 11a. It is located at the center in the thickness direction (FIG. 11B). Next, as shown in FIG. 11B, the cutter bits 1 combined as described above are used.
1 and the supporting member 12 are inserted into the main body 4a from the inside of the machine through the space between the stoppers 6 of the frame 3. Next, FIG.
As shown by the two-dot chain line in FIG. 1B and the solid line in FIG. 8B, the two support members 12 are moved away from each other toward the inner wall of the main body 4a. By doing so, the two supporting members 12 are in contact with the cutter bit base 11a, and both side edges thereof are in contact with the two surfaces on the frame side in the figure in the main body 4a, and the bottom portions thereof are the stoppers of the frame 3. 6
, And the upper edge thereof is locked to the locking piece 4b of the main body 4a. Then, the two support members 12 are at that position, as shown in FIG.
10, the cutter bit 11 is fixed to the stopper 6 of the frame 3 by the bolt 12b, and the cutter bit 11 is fixed to the support member 12 by the bolt 11b. As a result, the cutter bit 11 is mounted in the cutter holder 4.

As shown in FIGS. 7 and 10, the cutter bit 11 has a cutter portion 11c on its base 11a.
And the cutter portion 11c is provided with chips 11d on two opposing sides. By doing so,
The ground can be excavated with one cutter bit 11 regardless of the rotation direction of the cutter disk 2 (FIG. 1).

When the cutter bit 11 attached as described above is removed to the inside of the machine, the above-described attachment procedure may be reversed. That is, the bolts 11b, 12b
After removing (see FIGS. 7 and 8) the two support members 1
2 is slid to overlap at the center position of the cutter bit base 11a (see FIGS. 8 and 11). Then
When the two support members 12 are pulled out to the inside of the machine, the cutter bit 11 also moves to the inside of the machine. In order to reliably move the cutter bit 11 toward the inside of the machine, a bolt hole is also formed near the center of the cutter bit base 11a, and before the support member 12 is pulled out, the cutter bit 11 is supported by the bolt 11b. 12 may be fixed.

FIG. 9 shows the inside of the cutter holder 4 after the removal of the cutter bit 11 in this manner. When the roller cutter 5 is mounted on the cutter holder 2 in this state, it is performed in the same manner as in the related art.

That is, the procedure shown in FIGS. 6A to 6C may be performed in reverse. First, the bolt 9a is loosened and the tightening of the bearing cap 9 is released. Next, the opening side (spacer 8b side) of the rotary saddle 8 is directed toward the inside of the machine, and the roller cutter 5 is inserted into the main body 4a while guiding its angular shaft portion 5c into the groove 7c of the main body 4a. The spacer 8b of the rotary saddle 8 may be attached to the square shaft portion 5c in advance (see also FIG. 2), or may be attached after the square shaft portion 5c is inserted. After that, the rotary saddle 8 is rotated 180 ° together with the roller cutter 5 by a wrench or the like,
The stopper plate 10 is inserted, engaged with the hexagonal seat 5d of the roller cutter 5, and fixed by the bolt 10b.

[0042]

According to the present invention, the cutter bit can be replaced from the inside of the machine by using the cutter holder on which the roller cutter is mounted. Further, the cutter bit can be replaced with a roller cutter from inside the machine.

That is, when replacing the roller cutter with the cutter bit, the support member supporting the cutter bit is attached to the cutter holder while the roller cutter bearing member is still mounted after removing the roller cutter. Since it only has to be inserted and mounted, replacement work from the inside of the machine is easy.

Further, since the roller cutter bearing member is kept housed in the cutter holder, no particular care is required for its storage. In addition, since the work of attaching and detaching the bearing member is not required, the replacement work is also facilitated from this point.

[Brief description of the drawings]

FIG. 1 is a drawing showing an example of a tunnel excavator to which a cutter mounting mechanism of the present invention is applied, (a) is a front view,
(B) is a sectional view taken along line II of (a).

FIG. 2 is a partially cutaway perspective view showing a roller cutter mounting state in one embodiment of the cutter mounting mechanism of the present invention.

3A and 3B are views showing a cutter holder in the cutter mounting mechanism of FIG. 2, wherein FIG. 3A is a plan view and FIG.
(C) is a cross-sectional view taken along the line CC in (b).

4 is a view showing a main body of the cutter holder shown in FIG. 3, (a) is a cross-sectional view, and (b) is a cross-sectional view taken along line IV-IV of (a).

FIG. 5 is a sectional view taken along line VV of FIG.

6 is a cross-sectional view for explaining a roller cutter removal procedure in the cutter mounting mechanism of FIG. 2 in the order of (a), (b), and (c).

FIG. 7 is a partially cutaway perspective view showing a cutter bit attachment state in the cutter attachment mechanism of FIG. 2;

8A and 8B are views showing a cutter holder in the cutter mounting mechanism of FIG. 7, wherein FIG. 8A is a plan view and FIG.
(C) is a γ-γ line sectional view of (b).

FIG. 9 is a transverse sectional view showing a frame portion of the cutter holder of FIG. 7;

FIG. 10 is a sectional view taken along line XX of FIG.

11A and 11B are diagrams showing a procedure for mounting a cutter bit in the cutter mounting mechanism of FIG. 7; FIG.
(A) is a cross-sectional view corresponding to the XX line cross-section, and (b) is a XI-XI line cross-sectional view of (a).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Excavator 2 ... Cutter disk 3 ... Frame 4 ... Cutter holder 4a ... Body 4b ... Locking piece 5 ... Roller cutter 5c ... Square shaft part 5d ... Hex seat 6 Stopper 7 Engagement recess 8 Rotating saddle 8b Spacer 9 Bearing cap 10 Stop plate 11 Cutter bit 11a Base 12 Support Element

Claims (8)

[Claims] 1. A cutter mounting mechanism comprising: a box-shaped cutter holder formed on a cutter disc of a tunnel excavator; and a roller cutter bearing member mounted on an opposed inner wall surface of the cutter holder. A pair of support members each having a recess for supporting a base of the cutter bit, the support members being inserted into the cutter holder from the cutter chamber side of the tunnel excavator and detachably engaged therewith. A cutter mounting mechanism for a tunnel excavator configured to be mounted. 2. A box-shaped cutter holder fitted and attached to a cutter disk of a tunnel excavator, comprising: a pair of rotary saddles supporting both ends of a shaft of a roller cutter; A bearing cap for non-rotatably mounting therein, and a pair of support members formed with a recess into which the cutter bit fits, and the support member is provided with a cutter from the cutter chamber side of the tunnel excavator. A cutter holder for a tunnel excavator configured to be detachably attached to a holder body. 3. A box-shaped cutter holder formed on a cutter disk of a tunnel excavator, a roller-cutter bearing member mounted on an opposed inner wall surface of the cutter holder, and a roller-cutter bearing member. A cutter bit to be inserted, and a pair of support members formed with a recess into which the base of the cutter bit is fitted. The support member is locked to each of the opposed inner wall surfaces of the cutter holder portion. Locking portions are provided so as to face each other with a gap through which a support member can be inserted, and the support members are respectively moved to the locking portion side after being inserted into the cutter holder through the gap. A cutter mounting mechanism for a tunnel excavator configured to be locked by being locked. 4. The base of the cutter bit is formed so that the width of the base in that direction is substantially the same between the opposed inner wall surfaces of the cutter holder with the roller cutter bearing member mounted thereon. A cutter mounting mechanism for a tunnel excavator according to claim 3. 5. The base of the cutter bit is formed to have a dimension smaller than the outer diameter of the roller cutter in the in-plane direction of the roller cutter, so that a large amount of sediment is taken in between the base and the inner peripheral edge of the upper end of the cutter holder. 4. The cutter mounting mechanism for a tunnel excavator according to claim 3, wherein a gap is formed. 6. A cutter holder for a tunnel excavator according to claim 2, wherein a space between opposed inner wall surfaces of said cutter holder portion is formed to have substantially the same dimension as a thickness of a base portion of said cutter bit to be inserted. 7. The tunnel excavation according to claim 3, wherein the cutter bit has tips on two opposite sides, and the tips can be positioned in two circumferential directions when mounted on a cutter disc. Machine cutter mounting mechanism. 8. An engaging piece which can be engaged with an upper end edge of a support member is formed near an inner upper end of the cutter holder main body, and a gap for inserting the support member is formed near a lower end of the cutter holder main body. 3. The stopper according to claim 2, wherein a stopper is formed such that the lower end edge of the support member can be locked so that the width of the support member is substantially the same as that between the opposed inner wall surfaces of the cutter holder body. Cutter holder for tunnel excavator.