JP2024053368A - Pile driver control device - Google Patents

Abstract

[Problem] To provide a control device for a pile driver that can proceed with construction in accordance with the geological structure while taking a large auger lifting stroke. [Solution] A slide leader 16 is attached to a base leader 15 that is erected on a base machine 14 so that it can be raised and lowered, and an excavation auger 25 is attached to the slide leader so that it can be raised and lowered, and the power for raising and lowering the slide leader is generated by the extension and contraction drive of a hydraulic cylinder, and the power for raising and lowering the auger is generated by the rotation drive of a hydraulic motor. In the control device for the pile driver 11, a speed control unit is provided that executes speed control to proceed with excavation at a constant excavation speed, and the speed control raises and lowers the auger and slide leader simultaneously in opposite directions with a speed difference. [Selected Figure] Figure 1

Description

The present invention relates to a control device for a pile driver, and more specifically, to a control device for a pile driver equipped with an auger for excavation.

In general, pile drivers equipped with an auger for excavation that rises and falls along a leader are structurally limited in the excavation length per run (the length of one stroke of the auger rising and falling) by the length of the leader. For this reason, for relatively small pile drivers, leader devices have been proposed that are equipped with various mechanisms that allow the auger to have a large rising and falling stroke within a design range that balances transportability and workability (see, for example, Patent Documents 1 and 2).

Japanese Patent Application Laid-Open No. 10-121474 JP 2007-277869 A

All of the leader devices described in the patent documents are constructed by combining a movable member and a fixed member, and are equipped with a hydraulic drive device that slides the movable member in the length direction. However, while such hydraulic drive devices provide an auger lifting stroke, they tend to increase costs because of the increased number of dedicated parts required to establish the mechanism. In addition, the device is driven by a hydraulic motor (Patent Document 1) and by a hydraulic cylinder (Patent Document 2), which have different characteristics in terms of force and speed, and therefore cannot flexibly respond to changes in the geological structure depending on the site.

The present invention aims to provide a control device for a pile driver that can carry out construction according to the geological structure while allowing for a large auger lifting stroke.

To achieve the above object, the pile driver control device of the present invention has a slide leader attached to a base leader that is movably mounted on a base machine in front of the base leader, and an excavation auger attached to the slide leader so that it can be raised and lowered. The power for raising and lowering the slide leader is generated by the extension and contraction drive of a hydraulic cylinder, and the power for raising and lowering the auger is generated by the rotation drive of a hydraulic motor. The pile driver control device is equipped with a speed control unit that executes speed control to proceed with excavation at a constant excavation speed, and the speed control is characterized in that the auger and slide leader are raised and lowered simultaneously in opposite directions and with a speed difference.

The speed control is also characterized in that when the slide leader reaches the lift limit determined by the fully extended and fully retracted states of the hydraulic cylinder, the lifting and lowering motion of the slide leader is reversed, and the slide leader is raised and lowered at a speed that is accelerated or decelerated from the lifting speed before the reversal, taking into account the speed difference.

According to the pile driver control device of the present invention, the hydraulic cylinder drive that raises and lowers the slide leader attached to the base leader relative to the base leader and the hydraulic motor drive that raises and lowers the auger attached to the slide leader relative to the slide leader are each configured to be controllable, and a speed control section is provided that raises and lowers the auger and slide leader simultaneously in opposite directions and with a speed difference in order to proceed with excavation at a constant excavation speed. Therefore, while taking a large auger lifting stroke that cannot be obtained by hydraulic motor drive alone, the auger's descending speed is offset by the slide leader's ascending speed, and the excavation speed can be reduced stably and accurately. In particular, it is possible to proceed with excavation at an extremely low speed range close to 0 while maintaining the amount of hydraulic oil that allows the hydraulic motor to rotate stably, and high-precision constant speed control can be performed with an inexpensive configuration that uses general hydraulic parts as is. As a result, the adjustable range of the lifting speed is expanded compared to the conventional method, and construction can be carried out according to the various geological structures at the site.

1 is a side view of a pile driver to which a control device in one embodiment of the present invention is applied. 10 is a graph showing the correspondence between two drive methods in constant speed control.

1 and 2 are diagrams showing a control device according to an embodiment of the present invention applied to a pile driver. As shown in FIG. 1, the pile driver 11 is equipped with a base machine 14 consisting of a lower track body 12 equipped with crawlers and an upper rotating body 13 rotatably mounted on the lower track body 12, a base leader 15 erected at the front of the upper rotating body 13, and a slide leader 16 attached to the base leader 15 so as to be slidable in the length direction (the vertical direction in FIG. 1). In addition, a leader support 17 is provided at the front of the upper rotating body 13 to support the base leader 15 so that it can be raised and lowered. Furthermore, stabilizing jacks 18 are provided at four points on the front, rear, left and right of the upper rotating body 13, and a counterweight 19 is mounted at the rear end of the upper rotating body 13 to balance the pile driver 11.

The base leader 15 is supported from the rear by a lifting cylinder 20 so that it can rotate, and the front side is equipped with an engagement structure that slides the slide leader 16 in the length direction, and the upper side is equipped with a slide cylinder 21. Each cylinder 20, 21 is a typical hydraulically driven double-acting hydraulic cylinder with a predetermined stroke length. The slide leader 16 is formed as long as possible in consideration of transportability and workability, and a bracket 16a is provided on the rear surface of the middle part in the length direction to support the piston rod of the slide cylinder 21. A top sheave 22 around which a hanging rope is wound is attached to the upper end of the slide leader 16, and a lower guide 24 is attached to the lower end to prevent the construction member (e.g., rod) 23 from swinging, and an excavation auger (rotary drive device) 25 is attached to the front of the slide leader 16 so that it can be raised and lowered.

The auger 25 is driven to rotate by hydraulic pressure and applies a rotational force to the construction member 23 connected to the output shaft. A lifting chain 26 is stretched between a drive sprocket provided on one side of the upper and lower ends of the slide leader 16 and a driven sprocket provided on the other side, and both ends of the lifting chain 26 are attached to the top and bottom of the auger 25, respectively, to form a chain-type lifting device. Although not shown in the figure, the lifting device rotates the drive sprocket with a lifting drive hydraulic motor, and moves the lifting chain 26, which is wound around the drive sprocket and the driven sprocket, in the vertical direction, thereby lifting and lowering the auger 25 along the front surface of the slide leader 16. The lifting drive hydraulic motor is a fixed displacement hydraulic motor (e.g., a gear motor).

Here, the lifting drive hydraulic motor and the slide cylinder 21 have different hydraulic power sources (hydraulic pumps) and are driven either individually or both at the same time. The hydraulic power source is a multiple pump in which multiple hydraulic pumps are driven and rotated by a pump drive shaft directly connected to the engine, and by using two of these, separate hydraulic power sources are secured for the lifting drive hydraulic motor and the slide cylinder 21.

The auger 25 also includes a rotary drive hydraulic motor 25a connected to a reduction mechanism inside the device body, and an electromagnetic proportional pressure reducing valve (not shown) attached to the rotary drive hydraulic motor 25a. The rotary drive hydraulic motor 25a is a swash plate type variable displacement hydraulic motor whose capacity can be changed by changing the tilt angle of the swash plate. The tilt angle of the swash plate, i.e., the displacement volume (discharge volume per motor rotation), is adjusted by a regulator. This regulator is controlled by the control pressure output from the electromagnetic proportional pressure reducing valve.

The electromagnetic proportional pressure reducing valve changes the control pressure based on the control command of the construction management device implemented in the pile driver 11. Specifically, it is configured to change the degree of pressure reduction according to the increase or decrease in the control current input to the solenoid. When a control command is input, the generated command pilot pressure (secondary pressure) increases, and the motor is operated by gradually reducing the displacement volume by the operation of the regulator. On the other hand, when the control command is fixed to a minimum, the motor is operated by adjusting the displacement volume to a maximum. In other words, the control current and control pressure of the electromagnetic proportional pressure reducing valve are proportional to each other, but the control pressure and displacement volume are inversely proportional to each other. As a result, if the flow rate is constant, the smaller the displacement volume, the faster the motor will rotate, and the larger the displacement volume, the slower the rotation speed will be, but since it uses a lot of hydraulic oil to rotate, it generates a large torque.

When the pile driver 11 is used to bury a steel pipe pile, a steel pipe pile is used as the construction member 23. The steel pipe pile (not shown) is connected to the lower end of the output shaft of the auger 25 via a rod cap, and is driven by the rotary drive hydraulic motor 25a to lower the auger 25 while rotating the rod cap, thereby forcing it into the ground.

On the other hand, when the pile driver 11 is used for the purpose of ground improvement, as shown in FIG. 1, a rod is used as the construction member 23. The rod is rotated by the drive of a rotary drive hydraulic motor 25a, and its upper end is connected to a swivel joint 27 above the auger 25, while its lower end is connected to an excavation head 28. As a result, by lowering the auger 25 while rotating the rod, a ground improvement agent such as cement milk is sprayed from the tip of the excavation head 28 through the internal flow path of the rod and injected into the ground.

In recent years, as pile drivers 11 have become more multifunctional, when the pile driver 11 is used for the purpose of casing excavation, a casing (not shown) is used instead of the excavation head 28. The casing is connected to the lower end of the rod via a coupling. As a result, the cylindrical body of the casing is arranged concentrically with the rotation axis of the rod and rotates as one unit, and by lowering the auger 25 while rotating the rod, the excavation bit at the tip of the casing excavates the ground or cuts away obstacles such as old foundations.

To carry out these various construction works, inside the cab 29 in which the operator sits, devices such as operating levers and pedals, push button switches, and a touch panel display for driving, turning, raising and lowering and rotating the auger 25, raising and lowering the base leader 15, and raising and lowering the slide leader 16 are concentrated near the driver's seat for ease of use. In addition, a construction management device is installed as a control device electrically connected to these devices and an operation sensor (detection unit) that detects the operating status of the pile driver 11.

The construction management device is composed of a CPU that executes a control program for construction management (construction method control) and performs calculations such as data processing and judgment. It also includes a flash ROM that stores the control program, a RAM that temporarily stores various data during processing, a storage unit that stores construction plan data at the construction site and various data created by executing the control program during the actual construction, and a display that allows the operator to check the results of the control program on a display screen and enter data using a touch panel.

The multiple sensors constituting the operation sensor of the auger 25 include a lifting position sensor, a depth sensor, a torque sensor, and a rotation sensor. The lifting position sensor is composed of an auger lifting position sensor that detects the upper limit position and lower limit position of the auger 25 relative to the slide leader 16, and a leader lifting position sensor that detects the upper limit position and lower limit position of the slide leader 16 relative to the base leader 15. The auger lifting position sensor is, for example, a limit switch provided at the upper and lower ends of the slide leader 16. On the other hand, the leader lifting position sensor is, for example, a hydraulic switch that detects that the operating pressure is in a relief state when the slide cylinder 21 reaches the extension stroke end.

The depth sensor is a sensor that detects the amount of movement of the movable part of the pile driver 11 that corresponds to the excavation length (depth), and is composed of an auger movement sensor that detects the amount of movement of the auger 25, and a leader movement sensor that detects the amount of movement of the slide leader 16. The auger movement sensor is, for example, a rotary encoder that detects the rotation angle of the driven sprocket of the lifting device. On the other hand, the leader movement sensor is a linear encoder that detects the amount of extension and retraction movement (extension and retraction stroke) of the slide cylinder 21.

The torque sensor is a sensor that measures the rotational torque acting on the auger 25, and is composed of a drive pressure sensor that measures the drive pressure (pump load pressure) of the rotation drive hydraulic motor 25a, and a control pressure sensor that measures the control pressure. The drive pressure sensor is provided on the upper rotating body 13, and measures the pressure at the outlet of the main hydraulic pump. Meanwhile, the control pressure sensor is provided on the auger 25, and measures the pressure obtained by reducing the pressure oil from the pilot hydraulic pump with an electromagnetic proportional pressure reducing valve. The rotation sensor detects the gear teeth of the output mechanism with a proximity sensor, and counts the pulse signal.

The signals detected or measured by each sensor are transmitted to the construction management device, and the rotational torque (construction torque) is calculated as the construction load, for example, based on the driving pressure of the rotary drive hydraulic motor 25a and the displacement volume corresponding to the control pressure. The depth, lifting speed (feed speed related to the lifting and lowering operation), and cumulative number of rotations are also calculated based on signals measured by encoders and proximity sensors installed in each part.

The construction management device can also download control programs and construction plan data via a communication connection. The construction plan data is input in advance into a computer in the office based on a construction plan prepared based on the results of a boring survey (an example of a ground survey) at the construction site, and includes pile numbers as well as various construction target values associated with the pile numbers, such as the construction sequence, target depth, excavation speed (ascent and descent speed), rotation speed, and cement milk flow rate. For example, the excavation speed is set in detail for each depth interval in response to changes in the geological structure.

The input of construction plan data is performed by inputting pile position data in comparison with the construction drawings. Specifically, the construction site (the planned location for burying the pile) is specified in two-dimensional coordinates as a relative position (distance) from the origin on the coordinate system. The created construction plan data is uploaded to a data server on the network with the addition of location information such as the address of the construction site and the model number of the pile driver 11 that will perform the work. In addition, a control program for the construction method to be implemented based on the construction plan data and data on the setting parameters of the control program are also created and uploaded to the data server in the same manner.

The construction management device configured in this manner has a constant speed control mode in which an additionally incorporated excavation speed control program is executed to proceed with excavation at a constant excavation speed, and the auger 25 and slide leader 16 are raised and lowered simultaneously in opposite directions with a sufficient speed difference for excavation through calculations by the CPU, which functions as a speed control unit that controls the speed.

In the speed control in the constant speed control mode (constant speed control), when the slide leader 16 reaches the lifting limit determined by the fully extended and fully retracted states of the slide cylinder 21, the lifting motion of the slide leader 16 is reversed, and the slide leader 16 is raised and lowered at a speed that is accelerated or decelerated from the lifting speed before the reversal, taking into account the speed difference between the auger 25 and the slide leader 16. Meanwhile, at this timing, the lifting motion of the auger 25 is also reversed, and is accelerated or decelerated according to the speed (speed difference) that is accelerated or decelerated relative to the slide leader 16, and overall, the lifting motion continues in a direction approaching the ground.

For example, when speed control is started and the auger 25 descends at a speed of 0.5 m/min and the slide leader 16 ascends at a speed of 0.3 m/min, the absolute value of the speed difference between the auger 25 and the slide leader 16 is 0.2 m/min. As a result, the descending speed of the auger 25 becomes larger and more dominant, so excavation proceeds at a constant speed of 0.2 m/min. Here, when the speed control unit receives a detection signal from the leader ascending/descending position sensor indicating that the slide leader 16 has reached its ascending limit position, it immediately contracts the slide cylinder 21 to cause the slide leader 16 to descend. Then, the descending speed of the slide leader 16 immediately after reaching its ascending limit is set to 0.5 m/min, which is the speed obtained by accelerating the previous ascending speed (0.3 m/min) by the speed difference (0.2 m/min).

Meanwhile, the ascent speed of the auger 25, which at this timing has switched from descending to ascending, is set to 0.3 m/min, which is a speed that is slower than the previous descent speed (0.5 m/min) by the speed difference (0.2 m/min). As a result, after the slide leader 16 starts to descend, that is, after the direction of movement of the slide cylinder 21 is reversed, the descent speed of the slide leader 16 becomes dominant, but by simultaneously accelerating and decelerating the auger 25 and slide leader 16 with the speed difference, a balance is achieved, and excavation work can be continued while maintaining a constant speed of 0.2 m/min.

The reverse operation after the slide leader 16 reaches its lift limit changes the drive speed of both the hydraulic motor drive and the hydraulic cylinder drive, so hydraulic control is performed to adjust the amount of hydraulic oil supplied to each target so that the excavation speed before and after the change is constant. For example, the opening of a flow control valve (e.g., a solenoid valve) is adjusted to ensure a flow rate that can maintain the target speed even after switching. At this time, the amount of tracking delay caused by the motion characteristics of each actuator is taken into account in the adjustment value of the excavation speed control program, allowing for fine speed control.

Below, as an example, the case of automatically operating the pile driver 11 in a ground improvement method will be described. First, when the pile driver 11 is brought to the site, it is in a transport position with the base leader 15 laid horizontally, and naturally, work cannot be performed in this position. Although not shown in the figure, in this transport position, both the slide leader 16 and the auger 25 are held in their lowest limit positions, and this satisfies the transport restrictions when transporting by trailer or the like.

To change from such a compact transportation posture to a working posture capable of excavation work, the base leader 15 is raised by operating the machine, and then the slide leader 16 and auger 25 are raised and positioned at their respective upper limits (Fig. 1). The prepared rod (construction member 23) is then hung and connected to the output shaft of the auger 25. The rod is formed so that it can be extended, and therefore can be used with a length twice as long as the slide leader 16, for example. Although not shown in the figures, setup work can also be performed with the slide leader 16 positioned at its lower limit. In this way, the excavation head 28 is attached to the lower end of the rod, completing the work, and it is held in front of the slide leader 16 so that it can rotate and move up and down.

Here, when the excavation work is carried out, if the auger 25 is moved from the upper limit position Hx to the lower limit position Lx, the maximum lifting stroke X per operation (Xmax) can be obtained. On the other hand, if the slide leader 16 is moved from the upper limit position Hy to the lower limit position Ly, the maximum lifting stroke Y per operation (Ymax) can be obtained. Therefore, the maximum lifting stroke of the auger 25 is obtained by adding together the amount of movement Xmax by the lifting device that rotates the lifting drive hydraulic motor and the amount of movement Ymax by the slide leader 16 that extends and retracts the slide cylinder 21.

When the construction management device is turned on and started up, the basic program is executed and a login screen is displayed on the display. Here, when the worker logs into the system using their worker ID and sets conditions according to their purpose from the menu screen, the necessary construction management programs and construction plan data are downloaded, and the construction plan pile placement screen (pile selection screen) is displayed on the display, although this is not shown in the figure.

The construction plan pile placement screen is a display screen whose scale has been adjusted so that the entire construction site is displayed, and is displayed graphically in two-dimensional coordinates. For example, multiple pile display bodies shown as circles indicate the construction site, with the numbers inside the circles indicating the construction order, and the numbers on the outside indicating the pile number. When constructing a specific pile number, the pile driver 11 is aligned with the construction site (pile core), and then the target pile display body is selected by operating the touch panel. Then, with the display switched to the construction screen, excavation work is carried out as planned until the target depth is reached, while construction data is created. Various numerical data and graphs such as "pile number", "depth", and "construction torque" are displayed on the screen.

Here, the specific operation of the automatic operation when the excavation speed control program is executed will be explained with reference to the graph showing the correspondence between the two drive methods shown in Figure 2. Figure 2 is a graph showing an example of continuous operation in the constant speed control mode.

In addition, in Figures 2(A) and (B), the horizontal axis of the two-dimensional coordinate graph represents time change (t). On the other hand, the vertical axis in Figure 2(A) represents the lifting and lowering speed (v) of the auger 25 and slide leader 16, with the lifting and lowering of the auger 25 represented by a solid line and the lifting and lowering of the slide leader 16 represented by a dashed line. Furthermore, in Figure 2(B), the lifting and lowering strokes X, Y (l) of the auger 25 and slide leader 16 are shown. Furthermore, in the time change, M1 and M2 correspond to the lifting and lowering movements (directions) of the auger 25 and slide leader 16 represented by arrows M1 and M2 in Figure 1.

To start work, the operator operates the touch panel on the display, for example, with the constant speed control mode selected, operates the measurement button, and then tilts the operation lever. This causes the auger 25 to rotate the excavation head 28 while keeping it stationary relative to the slide leader 16, and the slide leader 16, which is driven by a hydraulic cylinder that can be driven at a relatively stable speed even in the low speed range, is lowered relative to the base leader 15, and the excavated soil is mixed and stirred with the ground improvement agent while the excavation head 28 forms a borehole in the ground.

At this time, from the initial state to time t0, as shown in the solid line graph in Fig. 2(A), the auger 25 stops (the lowering speed is 0 m/min), and as shown in the dotted line graph in Fig. 2(A), the slide leader 16 lowers at a constant speed of 0.2 m/min, and excavation proceeds. At this time, the auger 25 remains at the upper limit position Hx, and the stroke Y of the slide leader 16 starting from the lower limit position Ly gradually decreases as shown in the dotted line graph in Fig. 2(B). Then, when time t0 is reached, the stroke Y becomes minimum, and the leader lift position sensor detects the lower limit position Ly of the slide leader 16. After that, at time t1 (M1), as shown in the solid line graph of FIG. 2(A), the auger 25 descends at a speed of 0.5 m/min, and as shown in the dotted line graph of FIG. 2(A), the slide leader 16 ascends at a speed of 0.3 m/min, and both are raised and lowered simultaneously, obtaining a speed difference between the auger 25 and the slide leader 16, and excavation is carried out at a constant speed of 0.2 m/min. At this time, the stroke X of the auger 25 starting from the ascending limit position Hx gradually increases as shown in the solid line graph of FIG. 2(B). Meanwhile, the stroke Y of the slide leader 16 starting from the descending limit position Ly also gradually increases as shown in the dotted line graph of FIG. 2(B). Then, when time t1 is reached, the stroke Y becomes maximum (Ymax), and the leader ascending/descending position sensor detects the ascending limit position Hy of the slide leader 16.

When the speed control unit receives a detection signal from the leader lift position sensor indicating that the slide leader 16 has reached its lift limit, it immediately contracts the slide cylinder 21 to lower the slide leader 16. At this time, the descent speed of the slide leader 16 immediately after reaching its lift limit is set to 0.5 m/min, which is a speed that is accelerated by the speed difference (0.2 m/min) from the previous lift speed (0.3 m/min). Meanwhile, at this timing, the lifting operation of the auger 25 is reversed from lowering to lifting, and the lifting speed is set to 0.3 m/min, which is a speed that is decelerated by the speed difference (0.2 m/min) from the previous lowering speed (0.5 m/min). At this time, the auger 25 and the slide leader 16 are simultaneously accelerated and decelerated with the speed difference to balance, and the excavation speed (DS line) before and after switching is maintained at a constant speed of 0.2 m/min at time t1, as shown in FIG. 2 (A).

After that, from time t1 to time t2 (M2), as shown in the solid line graph of FIG. 2(A), the auger 25 ascends at a speed of 0.3 m/min, and as shown in the dotted line graph of FIG. 2(A), the slide leader 16 descends at a speed of 0.5 m/min, and both are raised and lowered simultaneously, obtaining a speed difference between the auger 25 and the slide leader 16, and excavation proceeds at a constant speed of 0.2 m/min. At this time, the stroke X of the auger 25 gradually decreases as shown in the solid line graph of FIG. 2(B). Meanwhile, the stroke Y of the slide leader 16, starting from the ascending limit position Hy, also gradually decreases as shown in the dotted line graph of FIG. 2(B). Then, when time t2 is reached, the stroke Y becomes minimum, and the leader ascending/descending position sensor detects the descending limit position Ly of the slide leader 16.

In this manner, in accordance with the hydraulic control of the speed control section, the auger 25 descends at a speed of 0.5 m/min and the slide leader 16 ascends at a speed of 0.3 m/min, and both are raised and lowered simultaneously from time t2 to time t3 (M1), obtaining a speed difference between the auger 25 and the slide leader 16, and excavation proceeds at a constant speed of 0.2 m/min. Then, when the slide leader 16 reaches its upper limit, the operations of both the slide leader 16 and the auger 25 are reversed, and from time t3 to time t4 (M2), the auger 25 ascends at a speed of 0.3 m/min and the slide leader 16 descends at a speed of 0.5 m/min, and both are raised and lowered simultaneously, obtaining a speed difference between the auger 25 and the slide leader 16, and excavation proceeds at a constant speed of 0.2 m/min.

When the speed control unit receives a detection signal from the auger lift position sensor indicating that the auger 25 has reached its lowering limit, it stops the lowering operation of the auger 25, immediately resets the lift state of the slide leader 16, and then lowers the slide leader 16. At this time, hydraulic control (oil volume control) is performed for the lowering operation of the slide leader 16 to match the speed difference (0.2 m/min) between the auger 25 and the slide leader 16, and with only the slide leader 16 driven independently, excavation proceeds at a constant speed of 0.2 m/min until the lowering limit position Ly is reached.

When the stroke (Xmax + Ymax) of the auger 25 and slide leader 16 is exhausted in this first operation, for example, the auger 25, which has released its grip on the middle part of the rod, is raised and re-gripped to grip the upper part (details omitted). This makes it possible to perform the second operation in constant speed control mode.

In this way, according to the control device of the pile driver 11 of the present invention, the hydraulic cylinder drive that raises and lowers the slide leader 16 attached to the base leader 15 relative to the base leader 15 and the hydraulic motor drive that raises and lowers the auger 25 attached to the slide leader 16 relative to the slide leader 16 are each configured to be controllable, and a speed control section is provided that raises and lowers the auger 25 and the slide leader 16 simultaneously in opposite directions and with a speed difference in order to proceed with excavation at a constant excavation speed. Therefore, while taking a large lifting stroke of the auger 25 that cannot be obtained by hydraulic motor drive alone, the descent speed of the auger 25 is offset by the rising speed of the slide leader 16, and the excavation speed can be stably and accurately reduced. In particular, it is possible to proceed with excavation at an extremely low speed range close to 0 (zero) while maintaining the amount of hydraulic oil that allows the hydraulic motor to rotate stably, and a constant speed control with high precision can be performed at a low excavation speed with an inexpensive configuration that uses general hydraulic parts as is. This expands the adjustable range of lifting speed compared to conventional methods, allowing construction to be carried out according to the diverse geological structures at the site.

In addition, in speed control, when the slide leader 16 reaches the lift limit determined by the fully extended and fully retracted states of the hydraulic cylinder, the lifting and lowering motion of the slide leader 16 is reversed and the slide leader 16 is raised and lowered at a speed that is accelerated or decelerated from the lifting and lowering speed before the reversal, taking into account the speed difference. This makes it possible to dramatically increase the excavation length at low speeds that cannot be achieved by lifting and lowering motion using only a hydraulic motor, and fully meets the needs for low-speed excavation, which have been increasing in recent years.

The present invention is not limited to the above-mentioned embodiment, and the control program may be simply configured to be added to an existing control device and function, and may be modified as appropriate according to the specifications of the pile driver and the type of excavation tool. The constant speed control may be performed according to a set speed, and may be applied to a limited narrow range as necessary. Furthermore, the embodiment has been described using an example of ground improvement, which generally has great advantages when performing constant speed control, but the present invention is not limited to this, and may also be applied to steel pipe burial and casing excavation. In this case, the specifications of the pile driver can be set widely, and for example, by configuring the lifting device as a known rack and pinion type, it is possible to provide multiple hydraulic motors that rotate and drive the pinion gears arranged in multiple stages. In addition, the configuration of the hydraulic circuit may also be modified as appropriate.

11...pile driver, 12...lower running body, 13...upper rotating body, 14...base machine, 15...base leader, 16...slide leader, 16a...bracket, 17...leader support, 18...jack, 19...counterweight, 20...elevation cylinder, 21...slide cylinder, 22...top sheave, 23...construction member, 24...lower guide, 25...auger, 25a...hydraulic motor for rotational drive, 26...lifting chain, 27...swivel joint, 28...digging head, 29...cab

Claims (2)

A control device for a pile driver, comprising: a slide leader attached to a base leader in a manner capable of being raised and lowered relative to the base leader in front of the base leader which is erected on a base machine in a manner capable of being raised and lowered; and an excavation auger attached to the slide leader in a manner capable of being raised and lowered; a power for raising and lowering the slide leader is generated by the extension and contraction drive of a hydraulic cylinder; and a power for raising and lowering the auger is generated by the rotation drive of a hydraulic motor;
A speed control unit is provided to perform speed control for proceeding with excavation at a constant excavation speed,
The speed control is characterized in that the auger and the slide leader are raised and lowered simultaneously in opposite directions with a speed difference. The control device according to claim 1, characterized in that the speed control reverses the lifting and lowering motion of the slide leader when the slide leader reaches a lifting and lowering limit determined by the fully extended and fully retracted states of the hydraulic cylinder, and raises and lowers the slide leader at a speed that is accelerated or decelerated from the lifting and lowering speed before the reversal, taking into account the speed difference.

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