JPH084474A - Middle bent type shield excavating machine - Google Patents

Abstract

PURPOSE:To allow a spreader at the top end to make contact with the end surface of a segment almost at right angle, even if a rod is extended, after the contraction of a shield jack, in the excavation work of a curved-shaped tunnel. CONSTITUTION:Each body top end part of a plurality of shield jacks 5 arranged, keeping an interval in the circumferential direction along the inner peripheral surface of a rear trunk 3 is supported in a swingable manner through a spherical bearing on the rear trunk 3. The part close to the body basic part of the shield jack 5 is grasped by a swing plate supported in a swingable manner at least in the horizontal direction for the inner peripheral surface front end part of the rear trunk 3, and one end of the swing jack 12 is pivotally installed at the inner peripheral surface front end part of the rear trunk 3, and the other end of the swing jack 12 is connected with the swing plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a center-breaking shield machine having a tubular body portion longitudinally divided into at least a front body and a rear body, and the front body and the rear body being flexibly connected. Regarding
More specifically, the present invention relates to a rear waist pushing center-fold type shield excavator of a type in which a shield jack first pushes the rear trunk and transmits it to the front trunk.

[0002]

2. Description of the Related Art The center-break type shield machine described above is capable of excavating a curved tunnel by bending the front and rear bodies. In this type of shield excavator, a segment wall is built behind the excavated tunnel, the spreader at the rod end of the shield jack is brought into contact with this segment wall, and the shield jack is extended to drive the shield excavation by the reaction force against the segment wall. It is common to excavate machines. For this reason, in excavation (hereinafter also referred to as bending) in excavation work in a curved tunnel, a shield jack fixedly fixed to the rear body is used, and the spreader at the end of the rod is brought into contact with the segment end surface, The left and right rods sandwiching the tunnel centerline should have a different extension amount according to the curve of the tunnel curve, that is, the rod extension amount on the outer diameter side (large curve diameter side) of the tunnel should be on the inner diameter side (small curve diameter side). If the rods are made larger than that, the center axis of the rear trunk of the shield machine is inclined with respect to the center axis of the segment wall at the most distal position, so the spreader that is in contact with the segment end surface slips. Unless it occurs, the rod bends as the rod extends and bends. Therefore, there arises inconveniences such as a seal in the protruding portion of the rod in the shield jack being damaged and causing oil leakage, or the rod being permanently deformed and not returning to the original contracted state.

Therefore, for example, Japanese Patent Laid-Open No. 64-17990.
As described in the publication, a shield jack is supported by a ring gutter portion of the rear body via a spherical bearing so as to be swingable in all directions, and a spreader at the rod end of the shield jack is attached to an inner peripheral surface of the rear body ( There is proposed a shield machine having a structure in which a shield jack is biased via a leaf spring so as to be in contact with a skin plate and slidably pressed.

[0004]

However, the shield machine described in the above publication also has the following disadvantages. That is, when the rod of the shield jack is extended and contracted, the spreader at the tip of the rod moves in contact with the skin plate of the rear body, which damages the skin plate and the expansion and contraction of the rod resists contact with the skin plate. I will not be able to move at high speed because I will receive it.

On the outer diameter side in the curved tunnel, the spreader at the rod end of the shield jack is brought into contact with the segment end face at a right angle. It is necessary to swing the side) so as to approach the inner peripheral surface side of the rear body. However, since all the shield jacks are biased so that the rod tip end side is in contact with the inner peripheral surface of the rear body by the leaf spring, the spreader at the rod tip end is greatly inclined with respect to the segment end face on the outer diameter side of the tunnel, There is a risk that the spreader may slip on the end face of the segment and the segment may be damaged.

The present invention has been made in view of the above-mentioned points, and when excavating a curved tunnel,
It is possible to prevent deformation of the rod of the shield jack and oil leakage from the jack seal part, and even if the rod is extended after contraction of the shield jack, the spreader at the tip can contact the segment end face almost at right angles. The purpose is to provide an excavator.

[0007]

In order to achieve the above-mentioned object, a center-folding shield machine according to the present invention comprises: a) a tubular body portion divided into at least a front body and a rear body in the longitudinal direction. hand,
In a middle-break type shield machine in which the front body and the rear body are flexibly connected, b) the main body tips of a plurality of shield jacks circumferentially arranged along the inner peripheral surface of the rear body. , Each of the shield jacks is swingably supported at least horizontally with respect to the rear body, and c) is swingably supported at least horizontally with respect to the front end of the inner peripheral surface of the rear body. The main body of each shield jack is configured such that one end of the swing jack is pivotally attached to the front end portion of the inner peripheral surface of the rear body while the other end of the swing jack is connected to the swing plate. The base side is configured to be swingable.

According to the second aspect of the present invention, d) the tip end of the main body of the shield jack can be swingably supported in all directions with respect to the rear body by a spherical bearing or a trunnion bearing.

According to a third aspect of the present invention, e) a sensor for detecting the most contracted state of the shield jack is provided, and the swinging jack is expanded / contracted based on the detection of this sensor, whereby the swinging plate is moved. The posture of the shield jack can be corrected so as to be parallel to the skin plate of the rear body.

As described in claim 4, f) a stroke meter is provided between the inner peripheral surface of the rear body and the rocking plate, and the moving direction of the rocking jack is determined based on the measured value of the stroke meter. The amount of movement may be controlled.

According to a fifth aspect of the present invention, g) a high pressure circuit and a low pressure circuit are provided in a hydraulic circuit for expanding and contracting the rocking jack, and a switching valve for switching between the two circuits is provided in the hydraulic circuit. The switching valve may be switched to the low pressure circuit side when the shield jack is extended, and the switching valve may be switched to the high pressure circuit side when the shield jack is contracted.

[0012]

According to the center-break type shield excavator of the present invention having the above structure, for example, in excavating a horizontally curved tunnel, when the shield excavator is excavated along the curve of the tunnel, The horizontal position of the shield jack between the outer diameter side and the inner diameter side of the rocking jack is extended or contracted so that the spreader at the tip abuts the segment end face at a right angle as much as possible regardless of the extension of the rod. , Can be corrected via the swing plate. As a result, the rod of the shield jack hardly bends, and permanent deformation of the rod and oil leakage from the jack seal portion are less likely to occur. In addition, when some seal jacks are contracted to install the segment (piece), the posture of the shield jack is returned to the original state through the swing plate by the expansion and contraction movement of the swing jack, so that the segment (piece ) Is incorporated, the shield jack can be expanded and contracted so that the spreader at the rod tip can be brought into contact with the end face of the newly incorporated segment (piece) at a substantially right angle. Furthermore, by holding the shield jack near the base of each shield jack, the swing range of the shield jack can be regulated within a certain range, and the interference between the shield jack and other equipment in the shield machine is prevented. Can be prevented. In addition, by gripping a plurality of adjacent shield jacks with the common swing plate, the number of swing jacks can be reduced compared to the number of shield jacks, so that the structure is simplified and Control of the rocking jack becomes easy.

In the shield machine according to the second aspect, the shield jack can be swung in all directions with respect to the rear body. Therefore, by making the swinging direction on the base side of the shield jack swingable in all directions, it becomes possible to excavate not only when the curved direction of the tunnel is the horizontal direction but also when it includes the vertical direction.

In the shield machine according to the third aspect, when the seal jack is returned to the original contracted state for the purpose of incorporating the segment (piece), the swing jack automatically detects the shield jack by the sensor. The posture is returned to the original state, that is, parallel to the skin plate of the rear body.

According to a fourth aspect of the shield machine, in the shield machine according to the third aspect, when the attitude of the shield jack is returned to the original state, the moving direction and the moving amount of the swing jack are measured by the stroke gauge. Automatically determined by Therefore, the operation depending on the intuition of the operator is not necessary.

In the shield machine according to the fifth aspect of the present invention, when the shield jack is extended, the hydraulic circuit for operating the swing jack is switched to the low pressure side. After abutting at a right angle, the posture of the shield jack naturally swings and changes so that the spreader is maintained at a right angle to the segment end face even if the rod is further extended. on the other hand,
When the shield jack contracts, the hydraulic circuit is switched to the high pressure side, so that the posture of the shield jack can be forcibly and quickly returned to the original state by the expansion and contraction movement of the swinging jack.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a center-break type shield machine according to the present invention will be described below with reference to the drawings. FIG. 1 is a vertical cross-sectional side view showing only a main part of the center-break type shield excavator according to the present embodiment, and FIG. 2 is a schematic rear view of the center-break type shield excavator as viewed from the rear. 3 is an enlarged sectional view showing the shield jack of FIG. 2 and its swinging device.
FIG. 4 is a cross-sectional plan view schematically showing a curved state of the center-bending shield machine of this embodiment.

As shown in FIG. 1, the shield machine 1 is
A cylindrical body is divided into a front body 2 and a rear body 3 in the longitudinal direction, and a connecting portion 3'having a slightly reduced outer diameter is integrally provided at the front end of the rear body 3 in a continuous manner. Is fitted in the rear end portion of the front body 2 and has a middle bending structure in which the front body 2 and the rear body 3 are flexibly connected via a sliding bearing 4. Along the inner peripheral surface of the rear body 3, the shield jacks 5 are arranged at regular intervals in the circumferential direction.
Has been arranged. Each shield jack 5 is swingably supported by attaching the tip of the jack body 5a to the front end of the rear body 3 via the spherical bearing 6 as shown in FIG. A spreader 7 is swingably connected to the tip of the rod 5b of the shield jack 5 via a spherical joint 7a. As shown in FIG. 1, a ring garter 8 is provided so as to project inward on the inner peripheral surface of the front end portion of the rear body 3 and the front body 2
The ring frame 9 is projected inward on the rear inner peripheral surface,
A center-breaking jack 10 is provided between the front and rear ring gutters 8 and the ring frame 9. As for the positional relationship between the center-folded jack 10 and the shield jack 5, as shown in FIG. 2 in this example, both the jacks 5 and 10 are displaced in the circumferential direction, and the center-folded jack 10 is placed inside. It is also displaced in the radial direction.

Now, the supporting structure of the shield jack 5 and its swinging device, which are the features of the present invention, will be described in detail.

As shown in FIG. 2, in this example, among the 12 shield jacks 5 arranged in the circumferential direction, three adjacent shield jacks 5 are gripped by a common arcuate swing plate 11. Has been done. That is, as shown in FIG. 3, the swing plate 11 has an opening 11 into which the main body 5a can be fitted and inserted at a position corresponding to the main body 5a of the shield jack 5.
b is formed and is gripped by inserting the main body 5a into the opening 11b.

Further, as shown in FIG. 2, the rocking plate 11 has a pair of laterally elongated guide holes 11a.
11a are provided in parallel, and the skin plate 3a of the rear body 3 is formed.
The rocking plate 11 is movably supported in the horizontal direction by slidably fitting the guide holes 11a into the distal end portion of the support tool 14 of which one end is supported. A pair of rocking jacks 12 are provided between the rocking plate 11 and the skin plate 3a at intervals in the circumferential direction. The swing jack 12 has a base side pivotally attached to the skin plate 3a and a tip end side of a rod 12a pivotally attached to the swing plate 11. Further, a stroke meter 13 is provided between the rocking plate 11 and the skin plate 3a so that the moving distance and the moving direction of the rocking plate 11 from the reference position can be detected. In addition,
A semicircular cutout 11 is formed on the inner peripheral side of the swing plate 11.
c is provided to prevent interference with the swing jack 12 when the swing plate 11 moves inward.

In this example, the shield jack 5 is oscillated only horizontally assuming that a tunnel curved only in the horizontal direction will be excavated. However, when excavating a tunnel curved in the vertical direction as well. Is the swing plate 1
It goes without saying that it is necessary to support movably 1 in the vertical direction and to provide a swing jack for moving the vertical direction.

In FIG. 1, a cutter disk, a drive device therefor, an erector for assembling segments, etc., which are essential to the shield machine 1, are not shown, but known ones are provided.

When excavating a straight tunnel, the medium-breaking shield excavator 1 of the present embodiment having the above-mentioned configuration has a shield on the end face of the segment wall where a segment wall is constructed behind the excavated tunnel. The spreader 7 at the tip of the rod 5b of the jack 5 is brought into contact with the rear body 3 by pushing the rear body 3 forward by extending the rod 5b, and the force is transmitted from the rear body 3 to the front body 2 to propel the excavator 1. Then, the cutter disk is rotated to perform excavation work.

When excavating a curved tunnel,
Similar to excavation of a straight tunnel, with the spreader 7 at the tip of the rod 5b in contact with the end surface of the segment S wall,
As shown in FIG. 4, the shield machine 1 is bent by extending the rod 5b of the shield jack 5 on the outer diameter side of the tunnel T larger than the rod 5b on the inner diameter side according to the curve (R) of the tunnel T. It advances. At this time, the forward distance of the rear body 3 (front body 2) on the outer diameter side of the tunnel becomes larger than the forward distance of the inner diameter side, and the central axis L of the rear body 3 is different from the central axis M of the segment wall at the most distal position. Tilts along the curve of the tunnel (tilt angle γ). In this example, since the front end (tip) of the main body 5a of the shield jack 5 is swingably supported via the spherical bearing 6, on the outer diameter side of the tunnel T, the base end side of the shield jack 5 is the front body 2. It swings in the direction approaching the inner peripheral surface (inclination angle α), and on the inner diameter side of the tunnel T, the base end side of the shield jack 5 swings in the direction separating from the inner peripheral surface of the front case 2 (inclination angle β). . The spreader 7 also swings in a certain range via the spherical joint 7a. Therefore, the spreader 7 at the tip of the rod 5b is always maintained substantially at right angles to the end face of the segment at the most distal position, so that bending of the rod 5b and cracking of the segment are prevented.

When the amount of extension of the rod 5b of the shield jack 5 on the outer diameter side of the tunnel reaches the maximum or near the maximum, the three shield jacks 5 at the position corresponding to one piece of the segment S, in this example. The rod 5b is contracted to the maximum and a new segment is assembled in the space. Then, the spreader 7 at the tip of the rod 5b of the shield jack 5 is brought into contact with the end surface of the newly assembled segment, but the posture of the shield jack 5 remains unchanged, that is, the base end side of the shield jack 5 is the front body 2. If the spreader 7 at the tip of the rod 5b is not in contact with the end surface of the segment at a right angle when the inner peripheral surface is kept close, the posture of the shield jack 5 is in an excavation start state, that is, the skin plate 3a of the rear body 3 is in contact. It is necessary to return to a posture parallel to. In this example, by extending the swing jack 12, the swing plate 11 is separated from the skin plate 3a of the rear body 3 inward in the horizontal direction, and the three shield jacks 5 are simultaneously returned to their original postures.

On the other hand, on the inner diameter side of the tunnel, when a new segment is assembled, the rod 5b is contracted to the maximum extent before the extension amount of the rod 5b reaches the maximum. Then, after returning the posture of the shield jack 5 to the excavation start state, the rod 5b is extended to bring the spreader 7 at the tip of the rod 5b into contact with the end surface of the newly assembled segment at a substantially right angle. On the inner diameter side of the rocking jack 12, since the base end side of the shield jack 5 is far from the inner peripheral surface of the front case 2 toward the center line as shown in FIG.
By contracting, the swing plate 11 horizontally approaches the skin plate 3a side of the rear body 3, and the three shield jacks 5 simultaneously return to their original postures. By repeating such work, the assembling of the segments for one ring is completed. In addition, in the above-described center-bending jack 10, when excavating a curved tunnel, the front body 2 is bent with respect to the rear body 3 so as to correspond to the tunnel curve, and the thrust of the rear body 3 is applied to the front body 2. Used to convey and maintain its flexion.

By the way, the swing jack 12 is used for controlling the attitude of the shield jack 5 as described above. An example of a hydraulic circuit for operating the swing jack 12 will be described with reference to FIGS. 5 and 6. .

FIG. 5 is a hydraulic circuit diagram of the rocking jack, showing a state of switching to the low pressure side, and FIG. 6 shows a state of switching to the high pressure side in the hydraulic circuit diagram of FIG.

As shown in these figures, in the hydraulic circuit 21 of this embodiment, the pipe 31 from the oil pump 22 driven by the motor 23a is connected to the P port of the 4-port 3-position electromagnetic switching valve 24. Further, the pipe 32 to the oil tank 22 is connected to the T port of the switching valve 24. The pipe 31 is branched, and the branch pipe 31a is connected to the oil tank 22 via a relief valve 27 with an unloading function. One end of a pipe 33 is connected to the A port of the switching valve 24, a pilot check valve 25 is interposed in this pipe 33, and the other end of the pipe 33 is the main body 12 a of the rocking jack 12.
Connected to the base end of. Further, one end of a pipe 34 is connected to the B port of the switching valve 24, a pilot check valve 26 is interposed in this pipe 34, and the other end of the pipe 34 is connected to the tip of the main body 12a of the swing jack 12. .

A pipe 33 is branched, and a low pressure relief valve 37 and a high pressure relief valve 38 are connected in parallel to the branch pipe 33a via a 3-port 2-position electromagnetic switching valve 28, and a common pipe 33b is used to connect an oil tank. 22 is connected.
The pipe 33b and the pipe 33 are connected by a branch pipe 33c, and a check valve 39 is interposed in the branch pipe 33c. Further, a pipe 34 is also branched, and a low pressure relief valve 40 and a high pressure relief valve 41 are connected in parallel to the branch pipe 34a via a 3-port 2-position electromagnetic switching valve 29, and connected to the oil tank 22 by a common pipe 34b. Has been done. Further, the pipe 34b and the pipe 34 are connected by a branch pipe 34c,
A check valve 42 is interposed in the branch pipe 34c.

Further, the shield jack 5 is equipped with a limit switch 43 in this example as a sensor for detecting the most contracted state of the rod 5b. The switching valve 29 is switched. That is, when the limit switch 43 is OFF, the switching valves 28 and 29 are switched to the low pressure relief valves 37 and 40, and when the limit switch 43 is ON, the switching valves 28 and 29 are switched to the high pressure relief valves 38 and 41.
Switches. Further, the switching valve 24 is switched by a signal from the stroke meter 13 (FIG. 2) described above. That is, when the limit switch 43 is ON in the most contracted state of the shield jack 5, the direction in which the swing plate 11 is driven is determined by the measurement value of the stroke meter 13, and corresponds to the pressure oil supply direction of the swing jack 12. The switching valve 24 is switched so as to operate. Then, when the posture of the shield jack 5 is returned to the original state, that state is detected by the stroke meter 13 (FIG. 2), and the switching valve 24
Automatically switches to the neutral position. The shield jack 5 and the swing jack 12 shown in FIGS. 5 and 6 are jacks arranged on the inner diameter side of the tunnel.

As described above, the hydraulic circuit 21 for the swing jack 12 is constructed. When the shield jack 5 is extended, the switching valve 24 is in the neutral position as shown in FIG.
The switching valves 28 and 29 are switched to positions where the pressure oil flows to the low pressure relief valves 37 and 40. Therefore, the rod 5b of the shield jack 5 extends in parallel with the skin plate 3a of the rear body 3, and the spreader 7 at the tip is brought into contact with the end surface of the segment S at a right angle. Particularly, when the center line L of the rear body 3 is inclined with respect to the center line M of the segment wall S at the most distal position due to the difference in the amount of extension of the rod 5b on the outer diameter side and the inner diameter side in the curved portion of the tunnel T, As shown in FIG. 4, the postures of the left and right shield jacks 5 sandwiching the center line of the tunnel T are supported by the spherical bearings 6 so that the spreaders 7 at the tips of the rods 5b are maintained at right angles to the end surface of the segment S. Swing to each. This is because the hydraulic circuit 21 is on the low pressure side as shown in FIG. 5, and therefore, the swing jack 12 exhibits a slight resistance to a change in the posture of the shield jack 5, and the posture of the shield jack 5 changes. This is because it expands and contracts to allow.

On the other hand, when the rod 5b of the shield jack 5 is pulled back to the most contracted state and returned, it is necessary to forcibly return the shield jack 5 to the original posture, that is, the state in which it is parallel to the skin plate 3a of the rear body 3. Because there is
Based on the detection of the limit switch 43, as shown in FIG. 6, the switching valve 24 is switched to the position for supplying the pressure oil to the tip side of the jack body 12a, and at the same time, the switching valves 28 and 29 are pressurized to the high pressure relief valves 38 and 41. Switch to the position where oil flows. Therefore, the posture of the shield jack 5 is instantly returned to the original state by the extension movement of the swing jack 12.

Although one embodiment of the center-break type shield machine according to the present invention has been described above, the present invention can be carried out as follows.

A) The shield jacks 5 are gripped one by one by the rocking plate 11, and the postures of the shield jacks 5 are individually controlled via the corresponding rocking jacks 12.

B) The swinging direction of the shield jack 5 on the base side is changed not only horizontally but also vertically or omnidirectionally according to the direction of the curved portion of the tunnel to be excavated.

C) The rear body 3 of the tip of the shield jack 5
In addition to the spherical bearing 6, a trunnion bearing or a method of pivotally supporting only in the horizontal direction is used for the rocking support for the.

D) The cross-sectional shape of the body of the shield machine is not limited to a circular shape, and may be, for example, an elliptical shape, or even if the body is divided into a front body, a middle body, and a rear body in the longitudinal direction into three parts. The same applies to machines.

E) An air cylinder is used for the rocking jack 12 and is driven by an air pressure source.

[0041]

As is apparent from the above description,
The center-break type shield machine of the present invention has the following effects.

(1) The deformation of the rod of the shield jack and the oil leakage from the jack seal portion are prevented during the excavation in the curved tunnel excavation work, and the spreader at the tip is prevented even if the rod is extended after the shield jack contracts. It is brought into contact with the end faces of the segment at a substantially right angle.

(2) In the shield machine according to claim 2,
Since the shield jack can be swung in all directions with respect to the rear body, it is suitable for excavating a tunnel bent not only in the horizontal direction but also in the vertical direction.

(3) In the shield machine according to claim 3,
When the seal jack is returned to its original contracted state in order to install a new segment, the posture of the shield jack is automatically returned to the state in which it is almost parallel to the skin plate of the rear body by the swinging jack detected by the sensor. Therefore, it is convenient because no operation is required.

(4) In the shield machine according to claim 4,
When the posture of the shield jack is returned to the original state, the moving direction and the moving amount of the swinging jack are automatically determined by the stroke meter, which is effective in the shield machine according to claim 3.

(5) In the shield machine according to claim 5,
The hydraulic control of the swinging jack is automatically performed according to the operating condition of the shield jack, and the posture of the shield jack is controlled so that the rod tip of the shield jack always abuts the segment end surface at a right angle.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view as seen from a side, showing only a main part of a center-breakable shield excavator according to an embodiment of the present invention.

FIG. 2 is a rear view showing the outline of the center-bending shield machine shown in FIG. 1 as viewed from the rear.

FIG. 3 is an enlarged sectional view showing the shield jack of FIG. 2 and its swinging device.

FIG. 4 is a plan view cross-sectional view schematically showing a bent state of the center-bend type shield machine according to the present embodiment.

FIG. 5 shows an embodiment of a hydraulic circuit diagram of the swing jack, showing a state in which it is switched to a low pressure side.

6 shows a state in which the hydraulic circuit diagram of FIG. 5 is switched to a high pressure side.

[Explanation of symbols]

 1 shield machine 2 front body 3 rear body 5 shield jack 6 spherical bearing 7 spreader 10 middle bent jack 11 swing plate 12 swing jack 21 hydraulic circuit

Claims (5)

[Claims] 1. A center folding shield excavator in which a tubular body is divided into at least a front body and a rear body in the longitudinal direction and the front body and the rear body are flexibly connected to each other. A plurality of shield jacks arranged circumferentially along the inner peripheral surface of the rear body, at least horizontally swingably supported on the rear body at least in the horizontal direction; A swing plate that is swingably supported at least horizontally with respect to the ends grips the shield jacks near the base of the main body and pivotally attaches one end of the swing jack to the front end of the inner peripheral surface of the rear body. The other end of the swing jack is connected to the swing plate so that the main body base side of each shield jack can swing. 2. The tip of the shield jack body is
The center-break type shield machine according to claim 1, wherein the rear trunk is rotatably supported by a spherical bearing or a trunnion bearing in all directions. 3. A posture of the shield jack is provided via the swing plate by providing a sensor for detecting the most contracted state of the shield jack, and expanding and contracting the swing jack based on the detection of the sensor. 3. The center-break type shield excavator according to claim 1 or 2, wherein is modified so as to be parallel to the skin plate of the rear body. 4. A stroke meter is provided between an inner peripheral surface of the rear body and the swing plate, and a moving direction and a moving amount of the swing jack are controlled based on a measurement value of the stroke meter. The center-break type shield machine according to claim 3. 5. A high pressure circuit and a low pressure circuit are provided in a hydraulic circuit for expanding and contracting the swing jack, and
A switching valve for switching between the two circuits is provided in the hydraulic circuit so that the switching valve is switched to the low pressure circuit side when the shield jack is extended and the switching valve is switched to the high pressure circuit side when the shield jack is contracted. The center-break type shield machine according to any one of claims 1 to 4.