JP2002201894A - Thrust load detecting device of shield machine-cutter driving shaft and load detecting method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To seize an accurate value of a front load at work by accurately detecting the front load in a boring advancing work process, that is, a thrust load acting on a cutter driving shaft. SOLUTION: In this thrust load detecting device of a shield machine-a cutter driving shaft for detecting the thrust load acting on the cutter driving shaft 3 in the boring advancing work process, the device is provided with a driving shaft displacement/strain converting-amplifying rod 5 arranged inside the cutter driving shaft 3, and having a load sensor 6 for detecting the thrust load, and a load monitor - recorder 12 arranged on a shield machine operation panel, and internally storing a strain measuring apparatus for clarifying a measured load value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a shield machine
The present invention relates to a thrust load detecting device for a cutter drive shaft and a method for detecting the load, and in particular, in a shield machine, detects an actual thrust load acting on the cutter drive shaft by a front load (excavation surface reaction force) during excavation work. The present invention relates to a shield thruster / cutter drive shaft thrust load detecting device and a load detecting method capable of safely operating by monitoring the thrust load at a remote place.

[0002]

2. Description of the Related Art The shield construction method is one of tunnel construction methods applied to soft ground. A shield excavator (or a shield machine) is used to protect the ground while preventing collapse of surrounding soil and soil in the ground. It is a method of building while propelling while excavating, safely taking in and taking out excavated earth and sand, and lining work inside the shield machine, and constructing a tunnel.

[0003] This shield excavator mainly comprises a cutter, a shield jack, a sediment intake device and an erector. The cutter is a device that excavates the ground while rotating, the shield jack is a device that advances the shield excavator, the earth and sand intake device is a device that extracts the excavated earth and sand according to the excavation speed, and the erector excavates A device for assembling a block (shield segment) made of cast iron or concrete in the back to construct a tunnel wall.

[0004] In the above-mentioned excavation work plan of the shield method using the shield excavator, the soil quality of the ground to be the excavation route is investigated in advance, and a shield machine adapted to the purpose of the construction and the nature of the soil is used. The cutter shape is selected empirically. Furthermore, in the excavation work, the cutter rotation speed according to the nature of the soil and the hydraulic pressure (propulsion speed) of the shield jack are set based on experience values, and excavation operations have been performed based on experience and intuition. .

Hitherto, the excavation operation of a shield machine often depends on an operation method mainly based on experience and the intuition of a skilled person. That is, in each scene during the excavation work, the front load (excavation surface reaction force) is extremely important and should always be quantitatively grasped. However, conventionally, there is no actual measurement method, so it is necessary to perform digging operation based on experience without grasping the front load, and sometimes the propulsive force of the shield jack and the front load (excavation surface reaction force) And the thrust bearing of the cutter drive shaft may generate an excessive thrust load. In other words, it has been pointed out that one of the reasons why the shield machine is not fully automated is that it is difficult to model a controlled object. Originally, the types of soils themselves varied widely, and even if the composition of the soil could be specified, the mechanical properties could not be determined simply.
It was considered common sense in this field.

Here, the excavation and excavation steps in the shield method are listed as follows. (1) First, an arc-shaped shield segment is assembled, a reaction force is taken from a cylindrical rigid body (tunnel wall) constructed by connecting the arc segments, and the entire shield machine is advanced by a stroke of a shield jack / piston. (2) With this advance, the soil layer in front of the shield machine is excavated by the rotating cutter, and the excavated earth and sand is taken into the shield machine by the screw conveyor, and further removed out of the tunnel by the belt conveyor. (3) When the space required for assembling the shield segments (jack stroke) is secured behind the shield machine and the rear of the shield machine, the piston of the shield jack is stored, and a new segment is assembled in the obtained space. Combine with the cylindrical part constructed in the step and extend the tunnel wall. By repeating the above cycle, the shield segments are sequentially added, and the length of the tunnel wall is further increased.

The following is a list of events encountered during the excavation operation due to soil-specific properties. (1) The thrust generated by the shield jack during excavation work of the shield machine is a loss component due to the frictional force due to the earth pressure that the shield machine body constantly receives from the surrounding soil layer and the reaction force received from the front soil layer during excavation. And only the remaining component (a part of the thrust) contributes to excavation at the cutter axis. (2) These loss components do not always take a constant value, but depend on the properties of the soil that change with time. (3) Since the mechanical properties of the soil layer are not always constant with respect to the excavation path, the excavation conditions cannot be set to a constant value, and the setting of the conditions must be sequentially changed according to the properties of the soil. . (4) Even if the composition of the soil is specified, it is difficult to simply determine the mechanical properties, so that the excavation conditions cannot be set constant. (5) When there is an earth pressure distribution in the soil layer in front of the excavation, or
Excavation conditions cannot be set constant even when there is a pressure gradient. (6) Excavation conditions cannot be set constant even when there is a density difference in the soil layer in front of the excavation and the excavation reaction force is partially different. (7) If the properties of the soil layer in front of the excavation are heterogeneous, there is a concern that there is a partial difference in the amount of excavation, lateral force (side force) acts on the shield machine, and the machine shifts to swinging or meandering. You.

[0008]

In the above-mentioned conventional excavation work process, as shown in FIG. 7, the actual working load value of the front load 1 (thrust acting on the cutter driving shaft 3) is sequentially detected.
There was no load detector and measuring device to display and record this quantitatively. In order to sequentially respond to various soil changes in the excavation route and perform an optimal excavation operation, the front load 1 (excavation surface reaction force) is constantly detected, and the excavation corresponding to the soil change is monitored while monitoring the load value. It was essential to equip the equipment for performing the operation.

In order to detect the actual value of the thrust load acting on the cutter drive shaft 1, a load detector which can be mounted on a drive shaft having a large diameter, can cope with a large load, and can withstand operation for a long period of time. Devising was indispensable. There is a problem that a system for setting a limit value for the thrust of the cutter drive shaft 1 to prevent the generation of excessive thrust is inadequate.

Further, since there is an uncertain factor in the frictional force or the like generated in the shield machine main body, setting the limit value for the thrust of the shield jack is difficult to determine for the above-mentioned reason. There has been a problem that a technology for detecting physical quantities such as jack hydraulic pressure (thrust), piston stroke, cutter driving torque, cutter shaft thrust, and the like and systematizing the correlation of these events has not been developed.

The present invention has been made to solve the above-mentioned conventional problems. That is, an object of the present invention is to detect a front load in the excavation work process, that is, a thrust load acting on the cutter drive shaft with high accuracy, so that an accurate value of the front load in the work can be grasped. An object of the present invention is to provide a thrust load detecting device for a drive shaft and a load detecting method thereof.

[0012]

According to the thrust load detecting device of the present invention, a thrust load detecting device for a shield excavator / cutter drive shaft for detecting a thrust load acting on the cutter drive shaft (3) in the excavation work process. A drive shaft displacement / displacement device provided with a load sensor (6) provided inside the cutter drive shaft (3) for detecting the thrust load.
A strain conversion / amplification rod (5), and a load monitoring / recording device (12) provided on a shield machine control panel and having a built-in strain measuring device for specifying an actually measured load value. A thrust load detecting device for a shield excavator / cutter drive shaft is provided.

The drive shaft displacement / strain conversion / amplification rod (5) is installed in the center of the cutter drive shaft (3) located between the cutter (2) and the thrust bearing (4). Are supported by internal bearings (3-1, 3-2), and the outer rings of the front and rear internal bearings (3-1, 3-2) are cylindrically formed in the axis of the cutter drive shaft (3). The inner rings of the front and rear interior bearings (3-1, 3-2) are fitted with the outer diameter of the drive shaft displacement / strain conversion / amplification rod (5), and the drive shaft is The shaft end of the stationary shaft (5-1) extending from the shaft end of the displacement / strain conversion / amplification rod (5) is
By fixing to the stationary shaft / fixed end (5-2), the drive shaft displacement / strain conversion / amplification rod (5) is maintained in a stationary state.

The shaft end of the stationary shaft (5-1) extending from the shaft end of the drive shaft displacement / strain conversion / amplification rod (5) is
By fixing to the stationary shaft / fixed end (5-2), the drive shaft displacement / strain conversion / amplification rod (5) can be kept stationary.

The load sensor (6) mechanically amplifies the small displacement (ΔL) generated in the axial direction of the cutter drive shaft (3) and electrically increases sensitivity on a bridge circuit. And a semiconductor strain gauge (6-1) is used as a strain detecting element.
The purpose is to increase the sensitivity.

In the thrust load detecting device having the above structure, the minute displacement (ΔL) generated in the cutter driving shaft (3) is transferred to the cylinder (3-1,
Transmitted to the fitted drive shaft displacement / strain conversion / amplification rod (5) via 3-2) and concentrated on the load sensor (6) provided in the drive shaft displacement / strain conversion / amplification rod (5). I do. Since the load sensor (6) is set to an extremely low rigidity relative to the rigidity of the drive shaft displacement / strain conversion / amplification rod (5), the minute displacement (ΔL) is mostly concentrated on the load sensor (6). I do. Therefore, by detecting the front load (1) and specifying the actually measured load value, the balance of the force during the excavation work can be constantly grasped, and the excavation operation can be performed in a visible manner.

Since the axial displacement itself of the cutter driving shaft (3) accompanying the action of the front load (1) is detected, a more accurate load form can be grasped. Further, since the load sensor (6) is located on the stationary side, by performing wired signal wiring, the entire system can be simplified, and the degree of occurrence of failure can be reduced.

According to the thrust load detecting method of the present invention,
A method for detecting a thrust load acting on a shield excavator / cutter drive shaft (3) during an excavation work, wherein the front drive (1) directly acts on the cutter drive shaft (3).
In the above, the minute displacement generated in the axial direction is detected and quantified by the drive shaft displacement / strain conversion / amplification rod (5) installed inside the cutter drive shaft (3), and is replaced with the front load (1). Accordingly, there is provided a method of detecting a thrust load of a shield excavator / cutter drive shaft, wherein an actual thrust load in an excavation work process is actually measured.

In the thrust load detecting method having the above structure, the front load (1) acts on all pressure receiving surfaces of the cutter (2), and the total load acts intensively as a thrust load on the cutter drive shaft (3). . The thrust load is balanced in the cutter drive shaft (3) between the cutter (2) and the thrust bearing (4), and the cutter (2) and the thrust bearing (4) have a very small force due to the thrust load. A displacement (ΔL) occurs. This minute displacement (ΔL) can be accurately detected and replaced with a front load value.

A cylinder bored on the axis of the cutter drive shaft (3) is defined as a gauge length (L) corresponding to a distance between the cutter (2) and the thrust bearing (4), and a front load is applied. By the action, the displacement generated on the cutter drive shaft (3) is reduced to a small displacement (Δ
L), and the length of the sensing part of the load sensor (6) is (L ')
And the gauge length (L) is N times the length of the sensing part (L ′), and the amount of strain (ε) generated in the cutter drive shaft (3).
Is set to ε = ΔL / L, and the minute displacement (ΔL) generated on the cutter drive shaft (3) is all transferred to the load sensor (6), and the minute displacement (ΔL) is changed with respect to the sensing portion length (L ′). [Delta] L), the strain ([epsilon] ') generated in the load sensor (6) is set to [epsilon]' = [Delta] L / L ', and the length of the gauge length (L) is determined by the length of the sensing part (L). ') N times (L = N · L'), and the distortion amplification factor (ε '/ ε) is set as ε' = N · ε.

In the load sensor (6), a lead wire for extracting an electric signal converted into a strain output is connected to a stationary shaft (5).
-1) Through the internal wiring hole (8-1), pulled out from the stationary shaft / fixed end (5-2) to the outside, and through the strain amplifier (10-3), the load monitoring / recording device (12). ) And displayed as a load value.

In this case, since the drive shaft displacement / strain conversion / amplification rod (5) and the stationary shaft (5-1) are on the stationary side, wired wiring processing becomes possible and contributes to simplification. .

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In addition, the same reference numerals are given to the common parts in the respective drawings, and the duplicate description will be omitted. FIG. 1 is a side sectional view of a shield excavator in a thrust load detecting device for a shield excavator cutter drive shaft and a load detecting method according to the present invention. FIG. 2 is a block diagram of the measurement system. As shown in the figure, the shield machine according to the present invention sequentially detects the front load 1 in the excavation work process, that is, the actual working load value of the thrust acting on the cutter 2 and the cutter drive shaft 3, and quantitatively detects this. It is equipped with a drive shaft displacement / strain conversion / amplification rod 5 incorporating a load sensor 6 for displaying and recording and a measuring device as shown in FIG.

In the shield machine according to the present invention, a drive shaft displacement / strain conversion / amplification rod 5 is provided inside the cutter drive shaft 3. A load sensor 6 for detecting a thrust load is installed in the drive shaft displacement / strain conversion / amplification rod 5,
The actual load 1 can be measured. Due to the front load 1 acting on the cutter 2, the axial thrust load generated on the cutter drive shaft 3 is transmitted to the load sensor 6, and the thrust bearing 4 in contact with the bottom surface of the load sensor 6 acts as a reaction force point to maintain the balance of force. Dripping. The thrust load applied to the load sensor 6 is equal to the strain gauge 6-6 constituting the load sensor 6.
At 1, it is converted into an electric signal and detected as a distributed load acting on the cutter drive shaft 3.

The load sensor 6 monitors the load value while constantly detecting the front load 1, that is, the reaction force of the excavation surface, in order to sequentially respond to various soil changes in the excavation route and perform an optimal excavation operation. In addition, the excavation operation corresponding to the change in soil quality can be performed. The load sensor 6 can detect the actual value of the thrust load acting on the cutter drive shaft 1, can be mounted on a drive shaft having a large shaft diameter, can handle a large load, and can operate for a long time. It is endurable.

Drive shaft displacement / strain conversion / amplification rod 5
Is installed at the axis of the cutter drive shaft 3 located between the cutter 2 and the thrust bearing 4. At both ends,
It is supported by the internal bearings 3-1 and 3-2. The outer rings of the front and rear inner bearings 3-1 and 3-2 are fitted to a cylinder formed in the axis of the cutter drive shaft 3, and the inner ring is fitted to the outer diameter of the drive shaft displacement / strain conversion / amplification rod 5. Therefore, by fixing the shaft end of the stationary shaft 5-1 extending from the shaft end of the drive shaft displacement / strain conversion / amplifying rod 5 to the stationary shaft / fixed end 5-2, the drive shaft displacement / strain conversion / strain conversion is performed. -The amplification rod 5 can maintain a stationary state.

The minute displacement ΔL generated on the cutter driving shaft 3 is:
The internal bearing 3-
Drive shaft displacement / strain conversion fitted via 1, 3-2
This is transmitted to the amplification rod 5 and this drive shaft displacement / strain conversion
It concentrates on the load sensor 6 provided in the amplification rod 5. Since the load sensor 6 is set to have extremely low rigidity relative to the rigidity of the drive shaft displacement / strain conversion / amplification rod 5, the minute displacement ΔL is mostly concentrated on the load sensor 6. 7 is a distortion signal output, and 8-1 is a lead wiring hole.

As shown in FIG. 2, the output of each load sensor 6 is input to a preamplifier 10 stored in a completely sealed / waterproof protective case 9 via a sensor cable provided inside a signal cable protective tube. You. The preamplifier 10 connected to the load sensor 6 converts a voltage input of the load sensor 6 into a current output, and converts the converted current signal via a signal line provided in the signal cable protection tube 11 to the load monitoring / recording device 1.
2 is input.

The load monitoring / recording device 12 has the following functions. (1) The signal from the load sensor 6 displays the maximum front load value during work by setting a peak hold in the digital indicator 13. Analog indicator 1
In 4, a limit value of the thrust load is set, a blue light emission is displayed when the load is within the limit, a red light is displayed when the load exceeds the limit, and an alarm is generated when a load exceeding the limit occurs. Call attention of the operator. The digital indicator 13 displays the maximum front load value during operation by a numeral.

(2) Each signal of the load sensor 6 is converted into an analog signal, and the data recording device 1 such as a data recorder is converted.
6, the signal is recorded, and the signal can be analyzed by the frequency analyzer 17 if necessary. (3) The signal from the load sensor 6 is input as a control signal 15 to the hydraulic control circuit of the shield jack, and is used as an emergency stop signal when an excessive thrust load occurs.

As described above, as shown in the control system of FIG. 2, in the present invention, in order to constantly measure the front load (excavation surface reaction force) during excavation work, the shield excavator cutter drive / cutter drive shaft is required. Equipped with a device to monitor and record the thrust load. By equipping this device,
Conventionally, it is possible to quantify the front load, which has depended on experience and intuition, and maintain the suitable conditions of jack propulsion speed corresponding to the magnitude of the load, enabling safe and optimal shield machine excavation operation .

FIG. 3 shows a structural example of a compression beam displacement sensor, and is a side view (a), a sectional view (b) and a circuit diagram (c). FIG. 4 is a side view (a), a cross-sectional view (b), and a circuit diagram (c) showing an example of the structure of a bent beam type displacement sensor. FIG. 5 shows a structural example of a shear beam type displacement sensor, and is a side view (a), a sectional view (b) and a circuit diagram (c). As the form of the load sensor 6, a compression beam displacement sensor (FIG. 3), a bending beam displacement sensor (FIG. 4), a shear beam displacement sensor (FIG. 5), or the like can be employed.
Along with mechanically amplifying this minute displacement, electrically
The sensitivity can be increased on a bridge circuit as shown and processed as a distortion signal.

FIG. 6 is a side sectional view of a shield machine showing another embodiment of the load sensor 6 having a strain amplification mechanism. When the output sensitivity is insufficient and the S / N ratio cannot be secured even with the thrust load detection method using the load sensor 6 of each of the above-described embodiments, the semiconductor strain gauge 6-1 is used as a strain detection element. , The sensitivity can be increased.

When the sensitivity is to be increased by using this strain detecting element, the thrust load is detected by the following procedure. The cylinder bored on the axis of the cutter drive shaft 3 has a length corresponding to the distance between the cutter 2 and the thrust bearing 4, which is referred to as a gauge length L. In addition, a minute displacement ΔL generated on the cutter drive shaft 3 due to the front load action is set. Further, the length of the sensing portion of the load sensor 6 is L ′, and the gauge length L is N of the sensing portion length L ′.
Double it. Here, the amount of strain generated on the cutter drive shaft is ε
Then, ε = ΔL / L, and a small displacement ΔL generated on the cutter driving shaft
However, if all shift to the load sensor section and a small displacement ΔL occurs with respect to the length L ′ of the sensing section, the strain ε ′ generated in the load sensor 6 becomes ε ′ = ΔL / L ′. . Here, assuming that the length of the gauge length L is N times the length of the sensing part L ', L = NL', so the strain amplification factor ε '/ ε is ∴ε ′ = N · ε, and the strain sensitivity is increased by the magnification of the gauge length L to the length L ′ of the sensing part. That is, the amount of strain in the load sensor 6 increases by N times the strain generated in the cutter drive shaft 3.

In the load sensor 6, a lead wire for extracting an electric signal converted into a strain output passes through a wiring hole inside the stationary shaft 5-1 and is drawn out from the stationary shaft / fixed end 5-2 to the outside. The signal is input to the load monitoring / recording device 12 via the strain amplifier 10-3 and displayed as a load value.
In this case, since the drive shaft displacement / strain conversion / amplification rod 5 and the stationary shaft 5-1 are on the stationary side, wired wiring processing becomes possible, which contributes to simplification.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

[0037]

As described above, the thrust load detecting device and the load detecting method for the cutter driving shaft of the shield machine according to the present invention have the following effects. (1) By detecting the front load and clearly indicating the actually measured load value, the balance of the force during the excavation operation is constantly grasped, and the excavation operation can be performed in a visible manner. (2) Since the axial displacement itself of the cutter driving shaft due to the action of the front load is detected, a more accurate load form can be grasped. Also, since the load sensor is located on the stationary side, by performing signal wiring by wire,
The entire system can be simplified, and the degree of failure can be reduced. (3) The dimensions of the “drive shaft displacement / strain conversion / amplification rod” can be arbitrarily adjusted according to the magnitude of the front load and the diameter and length of the cutter drive shaft, and the rated displacement of the load sensor By optimizing the sensing part length and the sensing part length, it is possible to cope with different conditions. (4) Since it is extremely simple in principle and very simple in structure, there are very few factors leading to failure. Therefore, in the shield machine which is forced to operate for a long time once it enters the operating state, it is possible to maintain the superiority in introducing the shield excavator with less fear of failure. (5) Since the axial displacement itself of the cutter drive shaft is detected, a more accurate load form can be grasped. In addition, since the load sensor is located on the stationary side, by performing wired signal wiring, the entire system can be simplified, and the degree of failure can be reduced.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a shield excavator in a thrust load detecting device and a load detecting method of a shield excavator cutter drive shaft of the present invention.

FIG. 2 is a block diagram of a measurement system.

FIG. 3 shows a structural example of a compression beam displacement sensor;
It is a side view (a), a sectional view (b), and a circuit diagram (c).

FIG. 4 is a side view (a), a cross-sectional view (b), and a circuit diagram (c) showing an example of the structure of a bending beam type displacement sensor.

FIG. 5 is a side view (a), a cross-sectional view (b), and a circuit diagram (c) showing an example of the structure of a shear beam type displacement sensor.

FIG. 6 is a side sectional view of a shield machine showing another embodiment of a load sensor provided with a strain amplification mechanism.

FIG. 7 is a configuration diagram of a conventional shield machine.

[Explanation of symbols]

 Reference Signs List 1 Front load 2 Cutter 3 Cutter drive shaft 3-1 Cutter drive shaft internal bearing (front) 3-2 Cutter drive shaft internal bearing (rear) 4 Thrust bearing 5 Drive shaft displacement / strain conversion amplification rod 5-1 Pinion 6 Load sensor 6-1 Strain gauge 7 Strain signal output 8-1 Lead wire wiring hole 9 Enclosed / waterproof protective case 10 Preamplifier 11 Signal cable protection tube 12 Load monitoring / recording device 13 Digital indicator 14 Analog indicator 15 Control signal Output 16 Data recording device 17 Frequency analysis device

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kenichi Nakasu 229 Togaya, Mizuho-cho, Nishitama-gun, Tokyo Ishikawajima-Harima Heavy Industries, Ltd. Mizuho Plant F-term (reference) 2D054 AC02 BA03 BB04 BB10 GA06 GA08 GA17 GA20 GA64 GA92 2F051 AA06 AB10 BA00

Claims (6)

[Claims] A thrust load detecting device for a shield excavator / cutter drive shaft for detecting a thrust load acting on a cutter drive shaft (3) in a process of excavation work, provided inside the cutter drive shaft (3). In addition, a drive shaft displacement / strain conversion / amplification rod (5) having a load sensor (6) for detecting the thrust load, and a strain gauge provided on a shield machine control panel for specifying an actually measured load value. A load monitoring / recording device (12) having a built-in measuring device, wherein a thrust load detecting device for a shield excavator / cutter drive shaft is provided. 2. The drive shaft displacement / strain conversion / amplification rod (5) is installed in the axis of a cutter drive shaft (3) located between the cutter (2) and a thrust bearing (4). Both ends are supported by internal bearings (3-1, 3-2), and outer rings of the front and rear internal bearings (3-1, 3-2) are bored in the axis of the cutter drive shaft (3). The inner rings of the front and rear inner bearings (3-1, 3-2) are fitted to the outer diameter of the drive shaft displacement / strain conversion / amplification rod (5). By fixing the shaft end of the stationary shaft (5-1) extending from the shaft end of the drive shaft displacement / strain conversion / amplification rod (5) to the stationary shaft / fixed end (5-2), the drive shaft displacement 2. The shield excavation of claim 1, wherein the rod is configured to maintain the strain / amplification rod in a stationary state. Thrust load detecting device of the cutter drive shaft. 3. The load sensor (6) mechanically amplifies a small displacement (ΔL) generated in the axial direction of the cutter drive shaft (3), and electrically increases sensitivity on a bridge circuit. And processes it as a strain signal. As a strain detecting element, a semiconductor strain gauge (6-1)
3. A thrust load detecting device for a shield excavator / cutter drive shaft according to claim 1 or 2, wherein the thrust load is used to increase the sensitivity. 4. A shield excavator in an excavation work process.
A method for detecting a thrust load acting on a cutter driving shaft (3), wherein the minute displacement generated in the axial direction of the cutter driving shaft (3) directly acting on a front load (1) is determined by the cutter driving shaft (3). The actual thrust load during the excavation work process is measured by detecting and quantifying the displacement / strain conversion / amplification rod (5) installed inside the shaft (3) and replacing it with the front load (1). A method for detecting a thrust load of a shield excavator / cutter drive shaft, characterized by: 5. A cylinder bored in the axis of the cutter drive shaft (3) is defined as a gauge length (L) corresponding to a distance between the cutter (2) and the thrust bearing (4), The displacement generated on the cutter drive shaft (3) by the action of the front load is defined as a minute displacement (ΔL), the length of the sensing portion of the load sensor (6) is defined as (L ′), and the gauge length (L) is the sensing portion length. (L ′), and the amount of strain (ε) generated in the cutter drive shaft (3) is ε =
ΔL / L, the minute displacement (ΔL) generated in the cutter drive shaft (3) is:
All are transferred to the load sensor (6), and the sensing part length (L ')
On the other hand, if a small displacement (ΔL) is generated, the strain (ε ′) generated in the load sensor (6) is expressed as ε ′ = ΔL /
L ′, the length of the reference point distance (L) is N times the length of the sensing part (L ′) (L = NL·L ′), and the strain amplification factor (ε ′ / ε) is ε ′ = 5. The method for detecting a thrust load on a shield driving machine and a cutter driving shaft according to claim 4, wherein N.epsilon. 6. In the load sensor (6), a lead wire for extracting an electric signal converted into a strain output passes through a wiring hole (8-1) inside a stationary shaft (5-1), and the stationary wire is stationary. A load monitoring / recording device (12) which is drawn out from the shaft / fixed end (5-2) and passes through a strain amplifier (10-3)
6. The method for detecting a thrust load of a shield excavator / cutter drive shaft according to claim 5, wherein the value is inputted to the thruster and displayed as a load value.