JP2000291385A - Excavator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-torque, variable speed, excavatable multi-functional excavator capable of switching a water jet injection pressure between high and low according to various soil conditions and presence of obstacles in wide excavating area and, as necessary, using a supply water into which abrasive material and additive agent are mixed. SOLUTION: An excavator comprises a mechanism and a plurality of water jet injection nozzles disposed in a cutter head 26 to switch an injection pressure between high and low. The mechanism drivingly rotating a center shaft 16 by the rotation of an external gear 35 through an inner cone 25 is so formed that a center shaft 16 positioned coaxially with an outer cone 17 is installed rotatably in a shield main body 2, an inner cone 25 crushing excavated matter in cooperation with the outer cone 17 is installed eccentrically on the center shaft 16, a cutter head 26 is installed on the center shaft 16, an internal gear 32 positioned coaxially with the center shaft is mounted on the inner cone 25, and the external gear 35 drivingly rotated by a drive motor 5 capable of variably controlling a plurality of speeds and torques is meshed internally with the internal gear 32.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an outer cone, wherein a center shaft concentric with an outer cone is rotatably provided on a shield body, and an inner cone for crushing excavated material in cooperation with the outer cone is provided eccentrically to the center shaft. The present invention relates to an improvement of an excavator in which a cutter head located in front of an inner cone is mounted on a center shaft. Switching between high-pressure injection and low-pressure injection of jet water according to the situation of the object, further mixing abrasives and additives into the jet water according to the situation, rotating the cutter drive motor during excavation,
The torque is variable and the excavation function of shielded and semi-shielded machines has been greatly improved.

[0002]

2. Description of the Related Art Conventionally, in a drilling machine such as a shield machine, an inner cone which is provided with a center axis concentric with an outer cone so as to be rotatable in a shield body and crushes excavated matter in cooperation with the outer cone is provided. It is known that a cutter head provided eccentrically to a center shaft and having a plurality of roller cutters (roller pits) is attached to a front end portion of a center shaft in front of an inner cone. In this device, a motor with a speed reducer is directly connected to the center shaft and the center shaft is rotationally driven, or an external gear that meshes with the motor with the speed reducer and the center shaft is provided and the center shaft is rotationally driven. And the cutter head is rotated. The center shaft is shaped like a crankshaft to mount the inner cone eccentrically to the outer cone. Is excavated.

[0003]

The excavation area,
The soil conditions for each location and depth are various, and even when assuming an excavated section in one section, ordinary soil,
In many cases, sandy soil, gravel, concrete layers, and the like are present in alternate layers, and in addition, rock layers may be present. It is difficult to excavate these soil conditions using one type of conventional excavator for the following reasons. (1) The optimum rotation speed and the optimum torque of the cutter differ for each soil condition, and the cutter shape must be changed to a shape suitable for the cutter. (2) The transport means of the excavated material must be selected according to the soil conditions, such as a fluid transport means, a screw conveyor transport means, and a slip transport means.

[0004] In particular, when the fluid transport means is employed, when transporting crushed excavated gravels, the size of the gravels that can be transported is determined by the diameter of the mud drainage pipe. You must use an excavator that can break into rubble. (3) When there is an obstacle such as a boulder or a concrete layer, it is necessary to use a powerful excavator that can be cut in advance and crushed in advance into a size that can take the boulder into the excavator.

[0005] The relationship between the rotation speed of the cutter and the torque for optimal excavation according to the soil conditions is generally as described below. Medium soil, sandy soil Medium-speed, medium-torque Gravel, gravel ground Low-speed, high-torque bedrock High-speed, low-torque
Conventionally, since it depends on the presence or absence of obstacles in the drilling layer,
It was the best to deal with ordinary soil, sandy soil, and gravel with a single excavator.

The present invention has been made in view of the above circumstances, and has been made in response to recent demands for civil engineering construction work. It is possible to excavate not only in various soil conditions but also in conditions such as concrete wall layers. The purpose of this is to provide a simple and multifunctional excavator, the jet water injection pressure can be switched between high and low according to the conditions of the soil and obstacles in the excavation area. Another object of the present invention is to provide an excavator in which a large-power drive motor can be easily arranged in a narrow shield body in order to change the torque and the number of revolutions of the cutter in multiple stages.

[0007]

According to a first aspect of the present invention, there is provided an excavator, wherein a center shaft concentric with an outer cone is rotatably provided on a shield body, and cooperates with the outer cone to crush excavated material. A cone is provided eccentrically with respect to the center shaft, a cutter head is provided in front of the inner cone, an internal gear coaxial with the center shaft is attached to the inner cone, and an external gear rotatably driven by a drive motor Are internally meshed with and meshed with the internal gear, the rotation of the external gear drives the center shaft via the inner cone, and the cutter head is provided with a plurality of jet injection nozzles. Is provided with a multi-hole pressurized water pipe that communicates with the jet injection nozzle. The excavation of an obstacle the natural ground, characterized in that it has to supply by switching the high-pressure water, respectively.

According to a second aspect of the present invention, in the excavator according to the first aspect, the supply water to the pressurized water pipe communicating with the jet injection nozzle is polished for cutting obstacles according to soil conditions. It is characterized in that an additive for splitting a material or an obstacle is mixed. As the abrasive, silica sand, glass fiber powder or the like is used, and as the additive, a conventional polymer is appropriately used.

According to a third aspect of the present invention, in the excavator according to the first aspect, the drive motor is an electric motor or a hydraulic motor. According to a fourth aspect of the present invention, in the excavator according to the first aspect, the drive motor controls a rotation speed and a torque according to soil conditions.

According to a fifth aspect of the present invention, in the excavator, the drive motor is a motor with a speed reducer, and the motor has a variable speed controlled by an inverter. According to a sixth aspect of the present invention, in the excavator according to the first aspect, a compound swivel joint for a water jet is provided on the center shaft.

According to the seventh aspect of the present invention, a composite pipe is provided on a center shaft and connected to an injection nozzle to enable the composite swivel joint to be perforated. In the excavator according to the eighth aspect, an injection nozzle for a water jet is disposed at the front end of the composite pipe via a pipe, and the water jet can be injected by selecting an injection nozzle at an appropriate position.

According to the ninth aspect of the present invention, the jetting direction of the water head can be freely set by attaching the jet nozzle to the cutter head at an arbitrary angle. Claim 10
In the excavator described in the above, a slit plate is fixed after the axis of the composite swivel joint, a slit is formed at a position similar to the position of the injection nozzle attached to the cutter head, and the position of the injection nozzle is detected. Have been.

The excavator according to the eleventh aspect is configured such that a lamp box is provided in front of the slit plate and a front target is provided behind the slit plate to detect the excavation direction. According to a twelfth aspect of the present invention, there is provided the excavator according to the first aspect, wherein a pinion gear is provided on an output shaft of each speed drive motor, and the pinion gear is inscribed in an internal gear rotatable with respect to the partition wall. By the meshing, the rotation of the motor is secondarily reduced, a drive shaft is concentrically mounted on the internal gear, and the external gear is mounted on the drive shaft.

According to a thirteenth aspect of the present invention, in the excavator according to the first aspect, an earth pressure detector is provided at a rear end of the center shaft, and an axial force received by the cutter head during propulsion is detected as an earth pressure. It is characterized by doing.

According to a fourteenth aspect of the present invention, in the excavator according to the first aspect, a gripper mechanism for preventing rolling of the shield body is provided on the shield body.
The gripper mechanism includes a hydraulic cylinder attached to the inner wall of the shield body and a rotating roller body for the gripper, and the rotating roller body for the gripper can advance and retreat toward the inner wall of the tunnel, and the pressing pressure against the inner wall of the tunnel is reduced. The pressure is adjusted by the hydraulic cylinder.

[0016]

1 to 3, a cylindrical tail shield cylinder 1 as a shield main body and a cylindrical front shield cylinder 2 as a shield main body are shown in FIGS. The tail shield cylinder 1 is the tail shield rear cylinder 1
A and tail shield front cylinder 1B and tail shield middle cylinder 1C
Consists of A sealing material 1D is provided at a connection portion between the tail shield middle cylinder 1C and the tail shield front cylinder 1B. Tail shield middle cylinder 1C and tail shield front cylinder 1B
Are connected via a direction correcting jack mechanism 4.

A partition 1 is provided at the front end of the tail shield front cylinder 1B.
E is provided. The gear case 3 is fixed to the partition 1E. A mounting plate 3A is fixed to the gear case 3. The motor 5 with a reduction gear is fixed to the mounting plate 3A. 6 is the output shaft.

A plurality of motors 5 with reduction gears are provided in the inner circumferential direction of the tail shield cylinder 1, and the number thereof is three as shown in FIGS. 5 and 6. Its output shaft 6
Is provided with an external tooth pinion 7. 8 is the gear stripper member.

In the tail shield cylinder 1, a composite pipe 9 is provided concentrically with the center axis of the tail shield cylinder 1. The composite pipe 9 is used for supplying water jet pressure water to a cutter head described later. A composite swivel joint 10 is provided at the rear of the composite pipe 9.

The composite pipe 9 is rotatably supported by a housing 9A installed on the partition wall 1D and a housing 9B installed on the mounting plate 3A via a bearing 9D. The housings 9A and 9B are sealed by oil seal members 9E and 9F. The composite pipe 9 is attached through the center 16. The composite swivel joint 10 is joined to the rear end of the composite pipe 9 for maintenance convenience.

By using the composite swivel joint 10, unlike the conventional single-hole swivel joint, the center shaft 16 is formed in the form of a composite pipe 9 having a plurality of through holes 9C for water jets as axes. Since it is housed inside, it is possible to realize a plurality of piping systems capable of injecting a plurality of water jets in a narrow space, and accordingly, a porous structure can be realized. Thus, at the front end of the composite pipe 9, the pipe 2
A water jet can be jetted from an appropriate jet nozzle 26D disposed through the nozzle 6E, and a pressure water pipe communicating with the jet jet nozzle for jetting the water jet supplies low-pressure water during excavation of the ground without obstacles. When excavating a ground with obstacles, high pressure water is switched and supplied. Thereby, any injection nozzle 2 can be selected according to the state of the face.
If 6D is selected, a water jet can be used without disturbing the face. Further, an abrasive or an additive is mixed with the water supplied to the water jet according to the condition of the excavation range, so that obstacles can be cut and cut to increase the excavation speed.

The excavator is used for the purpose of avoiding unnecessarily disturbing the ground and preventing the nozzle from being clogged with earth and sand at the time of normal ground excavation without obstacles such as boulders and driftwood. is using a low-pressure (140 kgf / cm ² or so), by switching to a high pressure (2,500 kgf / cm ² or so) injection by mixing abrasive or additive as needed when it encounters an obstacle, reliably obstacle only cut Primary crushing by cleavage. Additives increase the specific gravity of the water jet by several tens of percent and increase the impact force of the water jet, making it possible to more efficiently break or break obstacles. Therefore, the excavation is completed without disturbing the ground by the switching of the pressure and the composition of the jet water, so that the construction can be completely performed without any adverse effect such as the collapse of the ground surface. still,
The pressure of high-pressure water is approximately 1500 to 4000 kgf / c depending on the type of obstacle (cobble, driftwood, concrete layer, etc.).
Any pressure can be set within the range of m ² . The pump unit of this water jet is installed on the starting shaft separately for high pressure and low pressure.When excavating the normal ground, the low pressure water is constantly excavated by the low pressure pump through the pressurized water pipe. To the machine. When an obstacle comes out of the face, it switches to a high-pressure pump and supplies high-pressure water mixed with abrasives and additives as necessary to continuously excavate while crushing the obstacle. In this way, by properly using both or one of the pressure and the composition of the jet water, it is possible to carry out safe and reliable construction with high efficiency without disturbing the ground unnecessarily and removing obstacles. Also, due to the low-pressure water constantly supplied during the usual excavation of the ground, the clogging of the injection nozzle due to earth and sand is prevented.

Since the plurality of jet nozzles 26D can be attached to the cutter head 26 at an arbitrary angle, the jet direction of the water jet can be set freely on the center line of the excavator or in the outer peripheral direction.

The detection of the selected position of the jet nozzle 26D is a desirable step in order to match the position of the gravel on the surface of the cutter head 26 encountered during the excavation with the nozzle position. However, since the ejection nozzle 26D is attached to the cutter head 26, the nozzle position also rotates and changes as the cutter head 26 rotates.
In the past, there was a display that displayed the nozzle position by combining a gear with the rotating shaft, or a light emitting body attached to the rotating shaft, but the accuracy of the detection position, the complexity of the detection mechanism itself, and excessive cost However, in the present invention, a slit plate 52 is provided at the rear end of the shaft of the composite swivel joint 9.
9G is screwed, and the slit of the slit plate 52 is formed at a position similar to the position of the injection nozzle 26D attached to the cutter head 26. Therefore, accurate nozzle position can be confirmed by adding simple parts. is there.

The injection nozzle position detecting device has a lamp 58 incorporated in the lamp box 51 in front of the slit plate 52. A front target 53 made of a transparent acrylic plate is provided behind the slit plate 52, and the slit plate 5 is rotated by rotating the axis of the composite swivel joint 10.
2 also rotates, and the light of the electric lamp 58 in the lamp box 51 is irradiated to the front target 53 as a light spot from the circular slit of the slit plate 52 and is projected on the surface thereof. By projecting this light spot on the TV monitor on the operation panel outside the machine by the TV camera 56, the position of the injection nozzle can be confirmed.

A rear target 54 is mounted on a pointer mounting rod 48A coaxial with the swivel joint 10 behind the TV camera 56, and a laser beam from a laser device fixedly disposed behind the excavator. The passage is monitored to monitor the attitude of the forward moving portion of the excavator and the deviation from the normal line of the construction.

An internal gear 11 is provided on the partition wall 1E at a position eccentric from the center axis of the tail shield cylinder 1.
The internal gear 11 is rotatably supported by a metal 12 with a flange. The external gear pinion 7 is provided on the internal gear 11 in FIG.
Are inscribed and meshed as shown in FIG. Reference numeral 13 denotes an oil seal member, and reference numeral 14 denotes a nut for mounting a drive shaft described later.

A gripper mechanism 15 is provided at the rear of the tail shield rear cylinder 1A as shown in FIGS. This gripper mechanism 15 is a hydraulic cylinder 15
A and a rotary roller body 15B for grippers. The hydraulic cylinder 15A is mounted on the inner wall of the tail shield rear cylinder 1A, and the rotary roller body 15B for gripper is rotatably mounted on the tip of the piston rod.

The rotary roller body 15B for the gripper can be adjusted to advance from the rear tube 1A of the tail shield toward the inner wall of the tunnel by the hydraulic cylinder 15A, whereby the pressure applied to the inner wall of the tunnel can be adjusted to prevent rolling. Has become.

That is, conventionally, as a measure for preventing rolling, steel blades, beads, and the like are provided on the outer peripheral portion of the tail shield cylinder 1. However, an increase in the main pushing thrust due to an increase in ground resistance, and an increase in ground strength. Rolling prevention could not always be performed as expected by adjusting the gap with the excavator. However, according to the gripper mechanism 15, the pressing pressure against the inner wall of the tunnel can be controlled, and the expected rolling prevention effect can be obtained. .

As shown in FIGS. 1 and 3, partitions 2A and 2B are provided in the front shield cylinder 2, and a center shaft 16 is provided. The center shaft 16 is concentric with the center axis of the front shield cylinder 2.
An outer cone 17 is provided at the tip of the front shield cylinder 2. The outer cone 17 is concentric with the center shaft 16. The center shaft 16 is rotatably supported by a bearing cylinder 18. The bearing cylinder 18 is fixed to the partition walls 2A and 2B. Its center axis 16
Is hollow, and a composite pipe 9 penetrates this hollow portion.

The rear end of the center shaft 16 is reduced in diameter, and this reduced diameter portion is connected to an earth pressure detector 19 via a thrust bearing 21.
And serves as a detecting means for detecting earth pressure during excavation.

The front portion of the center shaft 16 is tapered. The inner cone 25
And the cutter head 26 are fitted. As shown in FIG. 7, the inner cone 25 is eccentric with respect to the center shaft 16 as shown by reference numeral e. The inner cone 25 and the cutter head 26 are fitted to the center shaft 16 so as to be integrally rotatable by keys 27 and 28, respectively.

The inner cone 25 is prevented from coming off the center shaft 26 by the nut 29,
The nut 6 is prevented from coming off from the center shaft 26 by the nut 30. The inner cone 25 is arranged at a position corresponding to the outer cone 17. The inner cone 25 is provided with crushing pieces 25A radially, and the outer cone 17 is provided with radial shear pieces 17A.

The diameter of the inner cone 25 is increased toward the rear, and the diameter of the outer cone 17 is decreased toward the rear. Crushing chamber 25C.

As shown in FIG. 8, a scraper 26A, roller bits 26B, 26C
Is mounted, and a plurality of jet injection nozzles 26F are arranged in a radial direction.

The jet injection nozzle 26F is connected to a water supply passage 9C of the composite pipe 9 via a pipe 26E. By the water jet injection by the jet injection nozzle 26F, the excavated material is primarily crushed into a size that can be taken into the crushing chamber 25C. 26F is a pipe cover.

At the rear end of the inner cone 25, the internal gear 3
2 are installed. A bearing 33 for receiving a radial load applied to the inner cone 25 is provided on an outer peripheral portion of the internal gear 32. The bearing 33 is fixed to a housing integrally formed with the partition walls 22A and 22B. In addition, 34 is a packing.

An external gear 35 is internally meshed with the internal gear 32. The external gear 35 is a drive shaft 3
6 is attached to one end by a gear stopper member 37. The drive shaft 36 is a bearing cylinder 1 fixed to the partition walls 2A and 2B.
8 is rotatably supported, and the other end is connected to the internal gear 11. 39 is a slip ring, and 40 is a nut for holding the slip ring.

The motor 5 with a speed reducer is an electric motor or a hydraulic motor. In the former case, the speed is changed by inverter control, and the relationship between the drive frequency, the torque curve and the output curve is, for example, as shown in FIG.

A mud feeding pipe 45 and a mud discharging pipe 46 are provided in the tail shield cylinder 1, and a seal case 45A is provided at the tip of the mud feeding pipes 45, 46. The tips of the mud feeding pipe 45 and the mud discharging pipe 46 face the mud chamber 47 on the rear side of the outer cone 17, and the mud chamber 47 communicates with the crushing chamber 25C. The outer cone 17 is provided with a large number of lattice plates 17B radially on the surface facing the muddy water chamber 47. The lattice plate 17 </ b> B serves to prevent the crushed excavated material of a certain size or more from being taken into the muddy water chamber 47. A partition plate 47A is provided between the sludge pipe 45 and the sludge pipe 46.
Is provided.

According to this excavator, when, for example, three motors with a speed reducer 5 are simultaneously rotated, three drive shafts 36 are driven via the output shaft 6, the external gear pinion 7, and the internal gear 11.
Is driven to rotate. The internal gear 32 has three drive shafts 3.
6, the inner cone 25 integrated with the internal gear 32 is rotated. This inner cone 25
The rotation of the center shaft 16 is driven by the rotation of the cutter shaft 26, and the cutter head 26 is rotated integrally with the center shaft 16.

The excavated material is primarily crushed by a water jet and sized to be taken into the excavator.
Secondary crushing is performed by the roller pits 26B and 26C of the cutter head 26, and then tertiary crushing to a size that can be taken into the mud discharge pipe 46 by cooperation of the inner cone 25 and the outer cone 17.

According to the embodiment of the present invention, the drive shaft 36 is provided at a position eccentric with respect to the center shaft 16, and the center shaft 16 is driven to rotate via the inner cone 25. Motor 5 to center shaft 1
The cost resulting from the water jet piping can be reduced as compared with the configuration directly connected to 6.

That is, in the motor having a structure in which the motor 5 with a speed reducer is directly connected to the center shaft 16, a motor with a special speed reducer having a through hole in the output shaft 6 for piping for water jet is provided. However, in the case of the embodiment of the present invention, the center shaft 16
The drive shaft 36 is provided at a position eccentric from the
Since the motor with speed reducer 5 is directly connected to the motor 6, no special motor with speed reducer is required, and the cost is reduced accordingly.

The internal gear 3 concentric with the center shaft 16
Since the inner cone 25 is relatively eccentric with respect to 2, the center shaft 16 can be of a straight rod shape that is not a crank shape. Therefore, the water jet composite pipe 9 is connected to the center shaft 16. The arrangement becomes easy.

Further, since the inner cone 25 is driven by meshing between the external gear 35 and the internal gear 32, a plurality of motors 5 with a high-power reducer are provided in the narrow shield cylinder 1 with a large power. Is possible.

[0048]

According to the present invention, as described above, the jet pressure of the water jet is switched between high and low in accordance with the soil condition of the excavation area and the state of the obstacle, or the cutting and cutting of the obstacle is performed. In order to make it more efficient, it is possible to mix the abrasive or additive with the injection water as needed to enable excavation under unprecedented obstruction conditions, and to easily mount a high-power motor with a reducer in a narrow shield body. It is possible to provide a multifunctional excavator which can be disposed and can excavate by changing the rotation speed and torque of the drive motor according to various soil conditions.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an excavator according to the present invention.

FIG. 2 is an enlarged sectional view of the tail shield cylinder shown in FIG.

FIG. 3 is an enlarged sectional view of the front shield cylinder shown in FIG.

FIG. 4 is a sectional view taken along line CC of FIG. 2;

FIG. 5 is a sectional view taken along line EE in FIG. 2;

FIG. 6 is a view of the inside of the rear cylinder of the tail shield of FIG. 2 viewed from behind.

FIG. 7 is a sectional view taken along line AA of FIG. 3;

FIG. 8 is a front view of the cutter head shown in FIG.

FIG. 9 is a sectional view taken along line BB of FIG. 3;

FIG. 10 is a diagram showing output torque characteristics of the motor with speed reduction shown in FIG. 1;

FIG. 11 is an enlarged plan view of the tail shield cylinder shown in FIG. 2;

FIG. 12 is an explanatory diagram of position detection of an injection nozzle and its display means.

[Explanation of symbols]

 2 Front shield cylinder (shield body) 5 Motor with deceleration 16 Center shaft 17 Outer cone 25 Inner cone 26 Cutter head 32 Internal gear 35 External gear

Claims (14)

[Claims] 1. A center shaft concentric with an outer cone is rotatably provided on a shield body, and an inner cone for crushing excavated matter in cooperation with the outer cone is provided eccentrically on the center shaft. A cutter head is provided in front of the internal gear, an internal gear coaxial with the center shaft is attached to the inner cone, and an external gear rotationally driven by a drive motor is in contact with and meshes with the internal gear, and the external gear The rotation of the gear rotates the center shaft via the inner cone, the cutter head is provided with a plurality of jet injection nozzles, and the center shaft is provided with a porous pressure water pipe communicating with the jet injection nozzles. The pressurized water pipe communicating with the jet injection nozzle supplies low-pressure water during excavation of an unobstructed ground. An excavator characterized in that high pressure water is switched and supplied when excavating a ground. 2. An abrasive for cutting obstacles or an additive for splitting obstacles is mixed with water supplied to a pressurized water pipe communicating with the jet injection nozzle according to soil conditions. The excavator according to claim 1, wherein: 3. The excavator according to claim 1, wherein the drive motor is an electric motor or a hydraulic motor. 4. The excavator according to claim 1, wherein the drive motor controls a rotation speed and a torque according to soil conditions. 5. The excavator according to claim 1, wherein the drive motor is a motor with a speed reducer, and is variable in speed by inverter control. 6. The excavator according to claim 1, wherein a composite swivel joint for a water jet is provided on the center shaft. 7. The excavator according to claim 6, wherein the composite swivel joint has a composite pipe formed on the center shaft, and is capable of supporting a hole connected to an injection nozzle for a water jet. 8. The water jet injection nozzle is arranged at a front end of the composite pipe via a pipe, and can select a proper position of the injection nozzle to jet a water jet. The excavator described. 9. The excavator according to claim 7, wherein the jet nozzle is attached to a cutter head at an arbitrary angle so that the jet direction of the water jet can be freely set. 10. A slit plate is fixed to the rear end of the shaft of the composite swivel joint, and a slit is formed at a position similar to the position of the injection nozzle attached to the cutter head to detect the position of the injection nozzle. The excavator according to any one of claims 6 to 9, which is configured as described above. 11. The excavator according to claim 10, wherein a lamp box is provided in front of the slit plate, and a front target is provided behind the slit plate to detect a direction of excavation. 12. An output shaft of each motor with a speed reducer is provided with a pinion gear, and the pinion gear is inscribed and meshed with an internal gear that is rotatable with respect to a partition so that rotation of the motor is secondary. The excavator according to claim 1, wherein the speed is reduced, a drive shaft is concentrically attached to the internal gear, and the pinion gear is attached to the drive shaft. 13. The earth pressure during excavation according to claim 1, wherein an earth pressure detector is provided at a rear end of the center shaft to detect a change in axial force of the cutter head. Excavator. 14. A gripper mechanism for preventing rolling of the shield main body is provided on the shield main body, the gripper mechanism comprising a hydraulic cylinder mounted on an inner wall of the shield main body and a rotary roller body for gripper. 2. The excavator according to claim 1, wherein the rotary roller body for the gripper is able to advance and retreat toward the inner wall of the tunnel, and a pressure applied to the inner wall of the tunnel is adjusted by the hydraulic cylinder. 3.