Drilling Hydraulic Systems

Abstract

To provide a hydraulic system for boring capable of detecting a twist in a boring shaft.SOLUTION: A hydraulic system 1A for boring according to an embodiment is loaded on a boring machine having a boring shaft in a telescopic structure, including a hydraulic motor 4 to rotate the boring shaft, a directional control valve 3 connected to the hydraulic motor 4 through a pair of supply / exhaust lines 41, 42, and a hydraulic pump 2 connected to the directional control valve 3 through the discharge line 22. Further, the hydraulic system 1A includes a pressure sensor 81 measuring discharge pressure of the hydraulic pump 2, a rotational speed sensor 73 measuring rotational speed of the hydraulic motor 4, and a controller 6 electrically connected to the pressure sensor 81 and the rotational speed sensor 73. The controller 6 determines occurrence of a twist in the boring shaft 17 when the discharge pressure of the hydraulic pump 2 measured with the pressure sensor 81 is larger than a first threshold and the rotational speed of the hydraulic motor 4 measured with the rotational speed sensor 73 is smaller than a second threshold.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a hydraulic drilling system onboard an excavator. [Background technology]

[0002] Conventionally, excavators for excavating vertical holes in the ground have been known. The excavator includes a vertically extending excavation shaft and an excavation bucket attached to the lower end of the excavation shaft. For example, Patent Document 1 discloses an excavator that rotates the excavation shaft using a hydraulic motor.

[0003] The excavator disclosed in Patent Document 1 also includes a control device that detects the N-value, which indicates the strength of the ground, during excavation. This control device calculates the N-value from the inlet pressure and rotation speed of the hydraulic motor. If the N-value becomes abnormal, the control device issues a warning that an obstacle that makes excavation impossible exists in the ground.

[0004] If the bucket hits an obstacle that cannot be excavated, such as hard rock, the bucket may bend, causing the vertical hole to be formed at an angle. However, if a warning is given of the presence of an obstacle that cannot be excavated in the ground as described above, it is possible to prevent the formation of an angled vertical hole. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-255765 Summary of the Invention [Problem to be solved by the invention]

[0006] When drilling a deep vertical hole in the ground, the drilling shaft has a telescopic structure. With such a long drilling shaft, when the bucket hits an obstacle such as hard rock and the drilling load increases, the drilling shaft is twisted significantly and the hydraulic motor stops. Therefore, when an operator reverses the rotation of the hydraulic motor, the twisting of the drilling shaft causes the hydraulic motor to rotate in the reverse direction at high speed, which may place excessive stress on the components of the hydraulic motor.

[0007] Therefore, an object of the present disclosure is to provide a hydraulic drilling system that can detect torsion of a drilling shaft with a telescopic structure. [Means for solving the problem]

[0008] From one aspect, the present disclosure provides a hydraulic excavation system to be mounted on an excavator having a telescopic drilling shaft, the hydraulic system comprising: a hydraulic motor for rotating the drilling shaft; a directional control valve connected to the hydraulic motor by a pair of supply and discharge lines; a hydraulic pump connected to the directional control valve by a discharge line; a relief valve provided in a relief line branching from the discharge line; a pressure sensor for measuring the discharge pressure of the hydraulic pump; a rotation speed sensor for measuring the rotation speed of the hydraulic motor; and a control device electrically connected to the pressure sensor and the rotation speed sensor, wherein the control device determines that a twist has occurred in the drilling shaft when the discharge pressure of the hydraulic pump measured by the pressure sensor is greater than a first threshold value and the rotation speed of the hydraulic motor measured by the rotation speed sensor is smaller than a second threshold value.

[0009] From another aspect, the present disclosure provides a hydraulic excavation system to be mounted on an excavator having a telescopic drilling shaft, the hydraulic system comprising: a hydraulic motor that rotates the drilling shaft; a directional control valve connected to the hydraulic motor by a pair of supply and discharge lines; a hydraulic pump connected to the directional control valve by a discharge line; a relief valve provided in a relief line branching from the discharge line; a pressure sensor that measures the inlet pressure of the hydraulic motor when the hydraulic motor rotates in the excavation direction; a rotation speed sensor that measures the rotation speed of the hydraulic motor; and a control device that is electrically connected to the pressure sensor and the rotation speed sensor, wherein the control device determines that a twist has occurred in the drilling shaft when the inlet pressure of the hydraulic motor measured by the pressure sensor is greater than a first threshold value and the rotation speed of the hydraulic motor measured by the rotation speed sensor is smaller than a second threshold value. [Effects of the Invention]

[0010] According to the present disclosure, twisting of the drilling shaft can be detected. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram of a hydraulic excavation system according to a first embodiment. [Figure 2] FIG. 2A is a side view of the excavator, and FIG. 2B is an enlarged view of the excavation unit. [Figure 3] 4 is a flowchart of control performed by a control device in the first embodiment. [Figure 4] FIG. 5 is a schematic configuration diagram of a hydraulic excavation system according to a second embodiment. [Figure 5] 10 is a flowchart of control performed by a control device in a second embodiment. [Figure 6] FIG. 10 is a diagram showing a modified example of the directional control valve. [Figure 7] FIG. 10 is a diagram showing another modified example of the directional control valve. [Figure 8] FIG. 10 is a diagram showing yet another modified example of the directional control valve. [Figure 9]FIG. 10 is a schematic configuration diagram of a modified example of a hydraulic excavation system. DETAILED DESCRIPTION OF THE INVENTION

[0012] (First embodiment) Fig. 1 shows a hydraulic system 1A for excavation according to a first embodiment. This hydraulic system 1A is mounted on an excavator 10 as shown in Fig. 2A.

[0013] The excavator 10 includes a frame 11 extending in the vertical direction, and a drilling unit 15 is attached to this frame 11. The drilling unit 15 includes a base 16 connected to the frame 11, an excavation shaft 17 extending vertically through the base 16, and a bucket 18 attached to the lower end of the excavation shaft 17. The excavation shaft 17 is supported on the base 16 so as to be rotatable and slidable in the vertical direction.

[0014] A reducer 19 is attached to the base 16, and the hydraulic motor 4 is attached to this reducer 19. The hydraulic motor 4 rotates the excavation shaft 17 via the reducer 19 in the excavation direction or the direction opposite to the excavation direction.

[0015] As shown in Fig. 2B, the excavation shaft 17 has a telescopic structure that can be extended or retracted. The excavation shaft 17 is moved up and down via a wire 13 by the hoisting unit 12 of the excavator 10, and is extended or retracted. More specifically, the excavation shaft 17 includes a plurality of tubular bodies of different diameters, and the n-th tubular body counting from the outside is at least partially fitted into the n-1-th tubular body. In the illustrated example, the number of tubular bodies is three, but is not particularly limited.

[0016] 1, the hydraulic system 1A includes the above-mentioned hydraulic motor 4 and a hydraulic pump 2 that supplies hydraulic fluid to the hydraulic motor 4 via a directional control valve 3. The hydraulic fluid is typically hydraulic oil.

[0017] More specifically, the hydraulic pump 2 is connected to a tank 20 by a suction line 21, and is connected to the directional control valve 3 by a discharge line 22. The directional control valve 3 is connected to the tank 20 by a tank line 25.

[0018] A relief line 23 branches off from the discharge line 22 and is connected to the tank 20. A relief valve 24 is provided in the relief line 23.

[0019] The hydraulic motor 4 has a first port 4a that serves as an inlet port when rotating in the excavation direction, and a second port 4b that serves as an inlet port when rotating in the opposite direction to excavation. In other words, when the hydraulic motor 4 rotates in the excavation direction, the second port 4b serves as an outlet port, and when the hydraulic motor 4 rotates in the opposite direction to excavation, the first port 4a serves as the outlet port.

[0020] The first port 4a and the second port 4b of the hydraulic motor 4 are connected to the directional control valve 3 by a pair of supply and discharge lines 41, 42. The supply and discharge line 41 is connected to the first port 4a, and the supply and discharge line 42 is connected to the second port 4b. The directional control valve 3 can be switched among a neutral position which is the middle position in Figure 1, an excavation position which is the right position in Figure 1, and a reverse rotation position which is the left position in Figure 1.

[0021] In the neutral position, the discharge line 22, the tank line 25, and the supply / discharge lines 41, 42 are blocked. In the excavation position, the discharge line 22 communicates with the supply / discharge line 41, and the supply / discharge line 42 communicates with the tank line 25. In the reverse rotation position, the discharge line 22 communicates with the supply / discharge line 42, and the supply / discharge line 41 communicates with the tank line 25.

[0022] In this embodiment, the directional control valve 3 is driven by a pilot pressure. Specifically, the directional control valve 3 includes a pair of pilot ports 31, 32. However, the directional control valve 3 may also be driven by an electric signal.

[0023] Furthermore, the hydraulic system 1A includes an operating device 5 for switching the directional control valve 3 from the neutral position to the digging position or from the neutral position to the reverse rotation position. The operating device 5 is arranged in the operator's cab of the excavator 10. The operating device 5 includes an operating lever that can be tilted in the digging direction or the counter-digging direction.

[0024] In this embodiment, the operating device 5 is a pilot operated valve that outputs a pilot pressure according to the tilt angle of the operating lever. For this reason, the pilot ports 31 and 32 of the directional control valve 3 are connected to the operating device 5 by pilot lines 51 and 52.

[0025] However, the operating device 5 may be an electric joystick that outputs an electric signal according to the tilt angle of the operating lever. In this case, the pilot ports 31 and 32 of the directional control valve 3 are connected to a pair of electromagnetic proportional valves, respectively.

[0026] The hydraulic system 1A further includes a control device 6. The control device 6 has a memory 61 capable of storing various data. The control device 6 is also electrically connected to a display device 91 and an alarm device 92.

[0027] With respect to the control device 6, the functions of the elements disclosed herein can be performed using circuits or processing circuits, including general-purpose processors, special-purpose processors, integrated circuits, application-specific integrated circuits (ASICs), conventional circuits, and / or combinations thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuitry. In this disclosure, a circuit, unit, or means is hardware that performs the recited functions or hardware that is programmed to perform the recited functions. The hardware may be hardware disclosed herein or other known hardware that is programmed or configured to perform the recited functions. Where the hardware is a processor, which is considered a type of circuit, the circuit, means, or unit is a combination of hardware and software, and the software is used to configure the hardware and / or processor.

[0028] The control device 6 is also electrically connected to the pressure sensor 81 and the rotation speed sensors 71 to 73. For example, each of the rotation speed sensors 71 to 73 is a magnetic speed sensor.

[0029] The pressure sensor 81 is provided in the discharge line 22 and measures the discharge pressure Pd of the hydraulic pump 2. The rotation speed sensor 71 is provided in the hoisting unit 12 as shown in FIG. 2A and measures the winding speed V of the wire 13 by the hoisting unit 12. Also as shown in FIG. 2A, the rotation speed sensor 72 is provided in a sheave attached to the upper end of the frame 11 and measures the excavation depth Dp from the rotation speed of the sheave. The rotation speed sensor 73 is provided in the hydraulic motor 4 as shown in FIG. 2B and measures the rotation speed N of the hydraulic motor 4.

[0030] However, it is possible to omit either one of the rotation speed sensors 71, 72. For example, the rotation speed sensor 72 may be omitted, and the digging depth Dp may be calculated by integrating the hoisting speed V. Alternatively, both of the rotation speed sensors 71, 72 may be omitted, and the control device 9 of the hydraulic system 1A may obtain the hoisting speed V of the wire 13 and the digging depth Dp from the control device of the excavator 10.

[0031] Next, the control performed by the control device 6 will be described with reference to FIG.

[0032] First, in step S1, the control device 6 compares the discharge pressure Pd of the hydraulic pump 2 measured by the pressure sensor 81 with a first threshold value α, and determines whether the discharge pressure Pd of the hydraulic pump 2 is greater than the first threshold value α. The first threshold value α is a value slightly smaller than the set pressure of the relief valve 24, i.e., the relief pressure. For example, when the relief pressure is 34 MPa, the first threshold value α is 32 MPa.

[0033] If the discharge pressure Pd of the hydraulic pump 2 is smaller than the first threshold value α, the control device 6 repeatedly compares the discharge pressure Pd of the hydraulic pump 2 with the first threshold value α. Conversely, if the discharge pressure Pd of the hydraulic pump 2 is greater than the first threshold value α, the control device 6 proceeds to step S2. In this embodiment, if Pd=α, step S1 is repeated, but if Pd=α, the control device 6 may proceed to step S2.

[0034] In step S2, the control device 6 compares the rotation speed N of the hydraulic motor 4 measured by the rotation speed sensor 73 with a second threshold value β, and determines whether the rotation speed N of the hydraulic motor 4 is smaller than the second threshold value β. The second threshold value β is an index for indicating whether the hydraulic motor 4 can be considered to be stopped, and is, for example, 100 rpm.

[0035] If the rotation speed N of the hydraulic motor 4 is greater than the second threshold value β, the control device 6 returns to step S1. Conversely, if the rotation speed N of the hydraulic motor 4 is less than the second threshold value β, the control device 6 proceeds to step S3. In this embodiment, if N=β, the control device 6 returns to step S1, but if N=β, the control device 6 may proceed to step S3.

[0036] In step S3, the control device 6 compares the excavation depth Dp measured by the rotation speed sensor 72 with a third threshold value γ and determines whether the excavation depth Dp is greater than the third threshold value γ. The third threshold value γ is, for example, 10 m. If the excavation depth Dp is smaller than the third threshold value γ, the control device 6 returns to step S1. Conversely, if the excavation depth Dp is greater than the third threshold value γ, the control device 6 proceeds to step S4. In this embodiment, if Dp=γ, the control device 6 returns to step S1, but if Dp=γ, the control device 6 may proceed to step S4.

[0037] In step S4, the control device 6 compares the winding speed V of the wire 13 measured by the rotation speed sensor 71 with a fourth threshold value ε, and determines whether the winding speed V of the wire 13 is smaller than the fourth threshold value ε. The fourth threshold value ε is, for example, 0.5 m / s. If the winding speed V of the wire 13 is greater than the fourth threshold value ε, the control device 6 returns to step S1. Conversely, if the winding speed V of the wire 13 is smaller than the fourth threshold value ε, the control device 6 proceeds to step S5. In this embodiment, if V=ε, the control device 6 returns to step S1, but if V=ε, the control device 6 may proceed to step S5. Note that the specific condition is satisfied when both step S3 and step S4 are YES.

[0038] In step S5, the control device 6 determines that a twist has occurred in the excavation shaft 17. On the other hand, while the process does not proceed to step S5, for example, while the above-mentioned specific condition is not satisfied, the control device 6 determines that a twist has not occurred in the excavation shaft 17. Furthermore, the control device 6 performs a specific action in step S5.

[0039] In this embodiment, the actions performed by the control device 6 include an action of causing the display device 91 to display that an abnormality has occurred, and an action of causing the alarm device 92 to issue an alarm. However, the control device 6 may also perform either the action of causing the display device 91 to display that an abnormality has occurred, or the action of causing the alarm device 92 to issue an alarm.

[0040] The control device 6 may display on the display 91 that an abnormality has occurred and may also display a warning on the display 91. The warning may be, for example, a warning that the operating lever should not be immediately tilted in the direction opposite to excavation, or a warning that a certain amount of time should be secured before the operating lever is placed in the neutral state.

[0041] Furthermore, when the control device 6 determines that twisting has occurred in the excavation shaft 17, it stores the date and time when twisting occurred in the excavation shaft 17, the discharge pressure Pd of the hydraulic pump 2, the rotation speed N of the hydraulic motor 4, the excavation depth Dp, and the winding speed V of the wire 13 in the memory 61. Therefore, if an abnormality occurs in the excavator 10, the cause of the abnormality can be investigated.

[0042] The hydraulic system 1A described above can achieve the following effects: When the bucket 18 hits an obstacle such as hard rock and the excavation load increases, the hydraulic motor 4 rotates while the excavation shaft 17 is twisted, causing the discharge pressure Pd of the hydraulic pump 2 to rise to the set pressure of the relief valve 24, which opens the relief valve 24 and stops the hydraulic motor 4. Therefore, the torsion of the excavation shaft 17 can be detected based on the discharge pressure Pd of the hydraulic pump 2 and the rotation speed N of the hydraulic motor 4.

[0043] Furthermore, in this embodiment, when certain conditions are not met, it is determined that no twisting has occurred in the excavation shaft 17, so cases in which it is determined that twisting has occurred in the excavation shaft 17 can be excluded from those in which it is determined that twisting has occurred in the excavation shaft 17, such as when removing soil and sand in which the excavation shaft 17 is rotated in reverse with the bucket 18 raised, or when winding up in which the winding speed V of the wire 13 is greater than the fourth threshold ε.

[0044] (Second embodiment) 4 shows an excavation hydraulic system 1B according to a second embodiment. In this embodiment, the same components as those in the first embodiment are given the same reference numerals, and redundant explanations will be omitted.

[0045] In this embodiment, a pressure sensor 82 is employed that measures the inlet pressure Pi of the hydraulic motor 4 when the hydraulic motor 4 rotates in the excavation direction. The pressure sensor 82 is provided in the supply / discharge line 41 that connects to the first port 4a of the hydraulic motor 4, and is electrically connected to the control device 6. Also, in this embodiment, the rotation speed sensors 71, 72 are not necessary.

[0046] Next, the control performed by the control device 6 will be described with reference to FIG.

[0047] First, in step S11, the control device 6 compares the inlet pressure Pi of the hydraulic motor 4 measured by the pressure sensor 82 with a first threshold value ζ to determine whether the inlet pressure Pi of the hydraulic motor 4 is greater than the first threshold value ζ. The first threshold value ζ is a value slightly smaller than the set pressure of the relief valve 24, i.e., the relief pressure. For example, when the relief pressure is 34 MPa, the first threshold value ζ is 32 MPa.

[0048] If the inlet pressure Pi of the hydraulic motor 4 is smaller than the first threshold value ζ, the control device 6 repeatedly compares the inlet pressure Pi of the hydraulic motor 4 with the first threshold value ζ. Conversely, if the inlet pressure Pi of the hydraulic motor 4 is greater than the first threshold value ζ, the control device 6 proceeds to step S12. In this embodiment, if Pi=ζ, step S11 is repeated, but if Pi=ζ, the control device 6 may proceed to step S2.

[0049] Step S12 is the same as step S2 described in the first embodiment. That is, the control device 6 returns to step S11 when the rotation speed N of the hydraulic motor 4 is greater than the second threshold value β, and proceeds to step S13 when the rotation speed N of the hydraulic motor 4 is smaller than the second threshold value β. In this embodiment, the control device 6 returns to step S11 when N=β, but may proceed to step S13 when N=β.

[0050] In step S13, the control device 6 determines that a twist has occurred in the excavation shaft 17. On the other hand, while the process does not proceed to step S13, the control device 6 determines that a twist has not occurred in the excavation shaft 17. Furthermore, the control device 6 performs a specific action in step S13. This action is the same as the action described in the first embodiment.

[0051] Furthermore, when the control device 6 determines that twisting has occurred in the excavation shaft 17, it stores the date and time when twisting occurred in the excavation shaft 17, the inlet pressure Pi of the hydraulic motor 4, and the rotation speed N of the hydraulic motor 4 in the memory 61. Therefore, if an abnormality occurs in the excavator 10, the cause of the abnormality can be investigated.

[0052] The hydraulic system 1B of this embodiment can provide the following effects: When the bucket 18 hits an obstacle such as hard rock and the excavation load increases, the hydraulic motor 4 rotates while the excavation shaft 17 is twisted, causing the inlet pressure Pi of the hydraulic motor 4 to rise to the set pressure of the relief valve 24, which opens the relief valve 24 and stops the hydraulic motor 4. Therefore, the torsion of the excavation shaft 17 can be detected based on the inlet pressure Pi of the hydraulic motor 4 and the rotation speed N of the hydraulic motor 4.

[0053] (Other embodiments) The present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present disclosure.

[0054] For example, the directional control valve 3 does not necessarily need to block the discharge line 22, the tank line 25, and the supply / discharge lines 41, 42 when in the neutral position. For example, as shown in Fig. 6, the directional control valve 3 may communicate the supply / discharge lines 41, 42 with the tank line 25 via a restriction when in the neutral position. With this configuration, when the directional control valve 3 is returned to the neutral position after the hydraulic motor 4 has stopped due to an increase in the excavation load, the hydraulic motor 4 can slowly rotate in the reverse direction so that the torsion of the excavation shaft 17 is gradually eliminated.

[0055] Alternatively, the pilot lines 51, 52 may be configured as shown in Fig. 7 so that the directional control valve 3 slowly returns to the neutral position. Specifically, a throttle 53 is provided in each of the pilot lines 51, 52, and a bypass line 54 that bypasses the throttle 53 is connected to the pilot line 51 or 52. A check valve 55 is provided in the bypass line 54, which allows flow toward the pilot port 31 or 32 but prohibits flow in the opposite direction.

[0056] Furthermore, when it is determined that twisting has occurred in the drilling shaft 17, the control device 6 may perform an action of maintaining the directional control valve 3 in the neutral position for a predetermined time after the directional control valve 3 is switched to the neutral position, instead of performing one or both of the action of displaying on the indicator 91 that an abnormality has occurred and the action of issuing an alarm in the alarm device 92. This predetermined time is, for example, until the discharge pressure of the hydraulic pump 2 becomes equal to or less than a predetermined value in the first embodiment, and until the inlet pressure of the hydraulic motor 4 becomes equal to or less than a predetermined value in the second embodiment. Note that the action of maintaining the directional control valve 3 in the neutral position for a predetermined time may be performed together with one or both of the action of displaying on the indicator 91 that an abnormality has occurred and the action of issuing an alarm in the alarm device 92.

[0057] For example, as shown in FIG. 8, an electromagnetic on-off valve 56 may be provided in a pilot line 52 connected to a pilot port 32 for switching the directional control valve 3 from the neutral position to the reverse rotation position, and when the control device 6 determines that a twist has occurred in the drilling shaft 17, the electromagnetic on-off valve 56 may be closed for a predetermined period of time.

[0058] Alternatively, in the case where the directional control valve 3 is driven by an electric signal, as in the modified drilling hydraulic system 1C shown in FIG. 9, when the operating lever of the operating device 5, which is an electric joystick, is tilted from the excavation direction to the direction opposite to excavation, the control device 6 may maintain the directional control valve 3 in the neutral position for a predetermined time and then switch it to the reverse rotation position.

[0059] If either the action of displaying the occurrence of an abnormality on the display 91 or the action of issuing an alarm on the alarm 92 is performed, the operator can be deterred from rotating the hydraulic motor 4 in reverse immediately after the excavation load increases and the hydraulic motor 4 stops. On the other hand, if an action is performed to maintain the direction switching valve 3 in the neutral position for a predetermined time when the direction switching valve 3 is switched to the neutral position, the torsion of the excavation shaft 17 can be eliminated while the direction switching valve 3 is maintained in the neutral position for the predetermined time.

[0060] In addition, after determining that a twist has occurred in the drilling shaft 17, when the operating lever of the operating device 5 is tilted in the direction opposite to drilling, causing the hydraulic motor 4 to rotate in the reverse direction and the rotation speed N of the hydraulic motor 4 exceeds a threshold value, the control device 6 may display on the display 91 that there is a risk of a malfunction and may issue an alarm in the alarm device 92.

[0061] Furthermore, since the hydraulic motor 4 includes a rotating unit consisting of multiple pistons and a cylinder block, etc., and a casing that houses this rotating unit, the pressure inside the casing can be measured by a pressure sensor, and when the pressure inside the casing exceeds a threshold value, the display 91 can display that damage has occurred, and the alarm 92 can sound an alarm.

[0062] (summary) From one aspect, the present disclosure provides a hydraulic excavation system to be mounted on an excavator having a telescopic drilling shaft, the hydraulic system comprising: a hydraulic motor for rotating the drilling shaft; a directional control valve connected to the hydraulic motor by a pair of supply and discharge lines; a hydraulic pump connected to the directional control valve by a discharge line; a relief valve provided in a relief line branching from the discharge line; a pressure sensor for measuring the discharge pressure of the hydraulic pump; a rotation speed sensor for measuring the rotation speed of the hydraulic motor; and a control device electrically connected to the pressure sensor and the rotation speed sensor, wherein the control device determines that a twist has occurred in the drilling shaft when the discharge pressure of the hydraulic pump measured by the pressure sensor is greater than a first threshold value and the rotation speed of the hydraulic motor measured by the rotation speed sensor is smaller than a second threshold value.

[0063] When the bucket hits an obstacle such as hard rock and the excavation load increases, the hydraulic motor rotates while the excavation shaft is twisted, causing the discharge pressure of the hydraulic pump to rise to the set pressure of the relief valve, which opens the relief valve and stops the hydraulic motor. Therefore, the torsion of the excavation shaft can be detected based on the discharge pressure of the hydraulic pump and the rotation speed of the hydraulic motor.

[0064] The control device may determine that a twist has occurred in the excavation shaft when a specific condition is satisfied when the discharge pressure of the hydraulic pump measured by the pressure sensor is greater than the first threshold value and the rotation speed of the hydraulic motor measured by the rotation speed sensor is less than the second threshold value, and the specific condition may be that the excavation depth is greater than a third threshold value and the winding speed of the wire by a hoisting unit that moves the excavation shaft up and down via a wire is less than a fourth threshold value. With this configuration, it is possible to exclude from cases in which a twist has occurred in the excavation shaft a situation in which the excavation depth is less than the third threshold value, such as when removing earth and sand in which the excavation shaft is rotated in the reverse direction with the bucket raised, and when hoisting, when the winding speed of the wire is greater than the fourth threshold value.

[0065] From another aspect, the present disclosure provides a hydraulic excavation system to be mounted on an excavator having a telescopic drilling shaft, the hydraulic system comprising: a hydraulic motor that rotates the drilling shaft; a directional control valve connected to the hydraulic motor by a pair of supply and discharge lines; a hydraulic pump connected to the directional control valve by a discharge line; a relief valve provided in a relief line branching from the discharge line; a pressure sensor that measures the inlet pressure of the hydraulic motor when the hydraulic motor rotates in the excavation direction; a rotation speed sensor that measures the rotation speed of the hydraulic motor; and a control device that is electrically connected to the pressure sensor and the rotation speed sensor, wherein the control device determines that a twist has occurred in the drilling shaft when the inlet pressure of the hydraulic motor measured by the pressure sensor is greater than a first threshold value and the rotation speed of the hydraulic motor measured by the rotation speed sensor is smaller than a second threshold value.

[0066] When the bucket hits an obstacle such as hard rock and the excavation load increases, the hydraulic motor rotates while the excavation shaft is twisted, causing the inlet pressure of the hydraulic motor to rise to the set pressure of the relief valve, which opens the relief valve and stops the hydraulic motor. Therefore, the twist of the excavation shaft can be detected based on the inlet pressure of the hydraulic motor and the rotation speed of the hydraulic motor.

[0067] When the control device determines that a twist has occurred in the excavation shaft, the control device may at least one of displaying the occurrence of an abnormality on a display device and issuing an alarm on an alarm device. With this configuration, it is possible to deter an operator from reversing the rotation of the hydraulic motor immediately after the excavation load increases and the hydraulic motor stops.

[0068] When the control device determines that a twist has occurred in the drilling shaft, the control device may maintain the direction switching valve in the neutral position for a predetermined time after switching the direction switching valve to the neutral position. With this configuration, the twist of the drilling shaft can be eliminated while the direction switching valve is maintained in the neutral position for the predetermined time.

[0069] The control device may include a memory, and when it determines that twisting has occurred in the excavation shaft, the control device may store in the memory the date and time when twisting occurred in the excavation shaft, the discharge pressure of the hydraulic pump or the inlet pressure of the hydraulic motor, and the rotation speed of the hydraulic motor. With this configuration, if an abnormality occurs in the excavator, the cause of the abnormality can be investigated. [Explanation of symbols]

[0070] 1A, 1B Drilling hydraulic system 10. Excavator 12 Hoisting unit 17 Drilling axis 2 hydraulic pumps 22 Discharge line 23 Relief Line 24 Relief valve 3-way valve 4 Hydraulic motor 41,42 Supply and discharge lines 6. Control device 61 memory 73 RPM sensor 81,82 Pressure sensors 91 Display 92 Alarm

Claims

1. A hydraulic drilling system mounted on an excavator having a telescopic drilling shaft, a hydraulic motor that rotates the drilling shaft; a directional control valve connected to the hydraulic motor by a pair of supply and discharge lines; a hydraulic pump connected to the directional control valve by a discharge line; a relief valve provided in a relief line branching from the discharge line; a pressure sensor that measures the discharge pressure of the hydraulic pump; a rotation speed sensor that measures the rotation speed of the hydraulic motor; a control device electrically connected to the pressure sensor and the rotation speed sensor, The control device determines that a twist has occurred in the drilling shaft when the discharge pressure of the hydraulic pump measured by the pressure sensor is greater than a first threshold value and the rotation speed of the hydraulic motor measured by the rotation speed sensor is smaller than a second threshold value.

2. The control device determines that a twist has occurred in the excavation shaft when a specific condition is satisfied when the discharge pressure of the hydraulic pump measured by the pressure sensor is greater than the first threshold value and the rotation speed of the hydraulic motor measured by the rotation speed sensor is smaller than the second threshold value, 2. The hydraulic drilling system of claim 1, wherein the specific condition is that the drilling depth is greater than a third threshold value and the winding speed of the wire by the hoisting unit that moves the drilling shaft up and down via the wire is smaller than a fourth threshold value.

3. A hydraulic drilling system mounted on an excavator having a telescopic drilling shaft, a hydraulic motor that rotates the drilling shaft; a directional control valve connected to the hydraulic motor by a pair of supply and discharge lines; a hydraulic pump connected to the directional control valve by a discharge line; a relief valve provided in a relief line branching from the discharge line; a pressure sensor that measures the inlet pressure of the hydraulic motor when the hydraulic motor rotates in the excavation direction; a rotation speed sensor that measures the rotation speed of the hydraulic motor; a control device electrically connected to the pressure sensor and the rotation speed sensor, The control device determines that a twist has occurred in the drilling shaft when the inlet pressure of the hydraulic motor measured by the pressure sensor is greater than a first threshold value and the rotation speed of the hydraulic motor measured by the rotation speed sensor is smaller than a second threshold value.

4. The control device, when determining that a twist has occurred in the drilling shaft, performs at least one of displaying that an abnormality has occurred on a display and issuing an alarm on an alarm. A drilling hydraulic system according to any one of claims 1 to 3.

5. The hydraulic drilling system according to any one of claims 1 to 4, wherein when the control device determines that a twist has occurred in the drilling shaft, the control device maintains the direction switching valve in the neutral position for a predetermined time after the direction switching valve is switched to the neutral position.

6. the controller includes a memory; The hydraulic system for drilling according to any one of claims 1 to 5, wherein when the control device determines that twisting has occurred in the drilling shaft, the control device stores in the memory the date and time when twisting has occurred in the drilling shaft, the discharge pressure of the hydraulic pump or the inlet pressure of the hydraulic motor, and the rotation speed of the hydraulic motor.

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