Remote monitoring system for hydraulic grab buckets

Abstract

To provide a remote monitoring system that monitors the status of the hydraulic unit of a hydraulic grab bucket from a location away from the grab bucket while the grab bucket is in operation, and utilizes the information obtained for control, deterioration failure detection, etc. [Solution] When the hydraulic grab bucket GB reaches its open or closed end position and reaches its mechanical limit of movement, the current or power value of the motor M that drives the hydraulic pump P decreases in hydraulic systems using a hydraulic pump P equipped with a variable discharge mechanism, and increases in hydraulic systems using a hydraulic pump P without a variable discharge mechanism. This information is observed from the power supply side of the motor M, and the normal operating state of the hydraulic grab bucket GB is monitored based on this information.

Description

Technical Field

[0001] The present invention relates to a remote monitoring system that monitors the state of a hydraulic unit of a hydraulic grab bucket from the power supply side and utilizes the information obtained therefrom for control and deterioration / failure determination.

Background Art

[0002] It is difficult to grasp the state of the hydraulic unit stored in the hydraulic grab bucket during the operation of the hydraulic grab bucket by an operator or a control panel located at a remote location. There is a need for a technology to remotely grasp the state based on the power supply information of the hydraulic grab bucket, and technologies for dealing with this have been proposed (see, for example, Patent Documents 1 to 3). Among the conventional technologies for remotely detecting failures of hydraulic grab buckets, in the method of detecting an oil temperature high signal that is emitted when the oil temperature becomes high, the damage at the time of failure is large, resulting in after-sales maintenance and often requiring a lot of time for recovery. For this reason, there has been a need for a system that can judge signs of deterioration in real time even during the operation of the hydraulic grab bucket before reaching a failure stop.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, the hydraulic unit of the hydraulic grab bucket is generally built into the inside of the hydraulic grab bucket suspended by a crane. Therefore, even if an anomaly detection sensor was installed inside the grab bucket, there were cost challenges in transmitting the sensor signal to the control panel. Furthermore, the inside of the grab bucket experiences significant shocks and vibrations during operation, which presented a challenge as an undesirable installation environment considering the durability of the sensors.

[0005] Incidentally, Patent Document 1 describes a technique for capturing closed-end and open-end signals from the power supply side using the peak value of the current in a system using a variable displacement pump. However, this method has the drawback that it can be difficult to capture the peak current when the load is high during gripping, and it is necessary to select a hydraulic pump with a larger capacity to reduce the load.

[0006] Furthermore, while a variable displacement pump utilizes a variable discharge mechanism to resolve hydraulic problems, a malfunction in this mechanism could potentially damage surrounding hydraulic equipment. Furthermore, even in hydraulic pumps without a variable discharge mechanism, there was a problem where continued operation after reaching the mechanical limit of the closed or open end position of the hydraulic grab bucket could lead to malfunctions such as an abnormal rise in oil temperature. Furthermore, when the hydraulic pump is located inside a sealed bucket, it is difficult to detect abnormal conditions, and there is a risk of continuing to operate in a malfunctioning state, which could increase damage to surrounding hydraulic equipment. Therefore, there was a need for technology to determine abnormal conditions while the hydraulic grab bucket is in operation. [Means for solving the problem]

[0007] The remote monitoring system for a hydraulic grab bucket of the present invention observes from the motor's power supply side that when the grab bucket reaches the mechanical limit of its open or closed position, the current or power value of the motor driving the hydraulic pump decreases in hydraulic systems using a hydraulic pump equipped with a variable discharge mechanism, and increases in hydraulic systems using a hydraulic pump without a variable discharge mechanism. Based on this information, the system monitors the normal operating state of the hydraulic grab bucket.

[0008] In the aforementioned system, when the hydraulic grab bucket reaches the mechanical limit of its open or closed position, a variable discharge mechanism is provided inside the hydraulic pump used in the hydraulic system to suppress the discharge amount. This is detected by a change in the current value or power value of the motor driving the pump, which indicates that the load on the pump has decreased due to the activation of the variable discharge mechanism, and a remote monitoring system is constructed to determine that the grab bucket has reached the open or closed position.

[0009] A remote monitoring system will be constructed that, when operating a hydraulic grab bucket, measures the current or power value of the motor driving the hydraulic pump after a specified time has elapsed for each grab bucket to reach its open or closed position, confirms that the current or power value is within the specified range corresponding to the load when the hydraulic pump reaches its mechanical limit, and determines that the oil flow control during load constraint is being performed correctly.

[0010] A remote monitoring system will be constructed that measures the time from the start of operation of a hydraulic grab bucket until it detects that the current or power value of the hydraulic pump drive motor is at the current or power value indicated when it reaches the mechanical limit of movement at the closed or open end position. The system will confirm that this time is within a specified range, and if the time exceeds the specified time, it will be determined that there has been an increase in oil flow resistance, such as filter clogging.

[0011] A remote monitoring system is constructed that, when a hydraulic grab bucket is opened or closed under stable load conditions, starts recording the current or power value of the hydraulic pump drive motor after the operation begins. When the current or power value indicating the open or closed position is detected, if the current or power value recorded before detection falls within a specified range, the system determines that the operation is normal.

[0012] A remote monitoring system is constructed that improves the reliability of both signals and the accuracy of determining whether each of the above signals is normal or abnormal by using both an open-end or closed-end position arrival signal, which is detected by a pressure switch when the hydraulic circuit pressure rises when the hydraulic grab bucket reaches the open-end or closed-end position, and a signal detected when the increase or decrease in the current value or power value of the motor driving the hydraulic pump falls within a specified range. [Effects of the Invention]

[0013] According to the hydraulic grab bucket remote monitoring system of the present invention, it is possible to remotely monitor the condition inside the sealed grab bucket while it is in operation. If an abnormality occurs in the components of the grab bucket, the abnormality can be immediately detected before secondary damage occurs, thereby improving the reliability of the hydraulic grab bucket. [Brief explanation of the drawing]

[0014] [Figure 1] This is an overall layout diagram showing one embodiment of a device configuration to which the present invention can be applied. [Figure 2] This is an explanatory diagram of the operation of a hydraulic grab bucket to which the present invention can be applied. [Figure 3] This is a hydraulic circuit diagram of one embodiment in which a hydraulic grab bucket to which the present invention can be applied uses a hydraulic pump having a variable discharge mechanism. [Figure 4] This is a hydraulic circuit diagram of one embodiment in which the present invention can be applied to a hydraulic grab bucket using a hydraulic pump without a variable discharge mechanism. [Figure 5]This is a time chart showing the change in load of an embodiment using a hydraulic pump with a variable discharge mechanism in a hydraulic grab bucket to which the present invention is applicable. [Figure 6] This is a time chart showing the change in load of an embodiment using a hydraulic pump without a variable discharge mechanism in a hydraulic grab bucket to which the present invention is applicable. [Figure 7] This is an explanatory diagram of signal detection of a remote monitoring system using a hydraulic pump with a variable discharge mechanism in a hydraulic grab bucket of the present invention. [Figure 8] This is an explanatory diagram of signal detection of a remote monitoring system using a hydraulic pump without a variable discharge mechanism in a hydraulic grab bucket of the present invention.

Embodiments for Carrying Out the Invention

[0015] FIG. 1 shows the arrangement of an embodiment to which the present invention is preferably applied. Generally, a hydraulic grab bucket GB is suspended from a crane CR by a wire rope WR, and a hydraulic unit OU is built into the hydraulic grab bucket. The crane operator OM and the control device CT are located remotely, and it is difficult to check the state of the hydraulic unit OU built into the hydraulic grab bucket GB during operation.

[0016] The power source for driving the hydraulic grab bucket GB is connected to the control device CT via a bucket power supply cable CA and through a crane wiring cable WL. The control device CT and the crane operator OM are located remotely. The control device CT and the crane operator OM may be arranged on the crane CR, but even in that case, they are in a remote position when viewed from the hydraulic grab bucket GB. The remote monitoring system of the hydraulic grab bucket of the present invention monitors the state of the hydraulic grab bucket GB that is remotely located at the position of this control device CT and grasps the state of the hydraulic grab bucket GB.

[0017] Figure 2 illustrates the operation of the hydraulic grab bucket GB. To grasp the bulk material TR, first, the hydraulic grab bucket GB in the fully open position shown in Figure 2 (1) is placed on top of the pile of bulk material TR, and the bucket shell (claws) CL is thrust into the pile of bulk material TR. Then, the hydraulic cylinder CY is operated and moved in the bucket closing direction CF to perform a grip, and it is operated to the gripped state shown in (2) of Figure 2. When transitioning from state (1) to state (2) in Figure 2, the bucket shell (claws) CL compresses the bulk material TR during operation. Therefore, the hydraulic cylinder CY is required to exert a large force to grip and operate the bucket shell (claws) CL. As it approaches the closed end position CP, it reaches maximum pressure, causing the variable discharge function or safety valve RV to activate. This can result in longer operating times or the operation stopping before reaching the closed end position CP, making the operating time unstable.

[0018] When moving the bucket from the gripped state (2) in Figure 2 to the open state (3) in the bucket opening direction OF, the movement is to release the compressed state, so the force on the hydraulic cylinder CY is small, and the opening operation can be performed by exerting a force that lifts the weight of the bucket shell (claw) CL. Since the magnitude of the load is stable during the opening operation, the operation time is also stable.

[0019] The operation of the hydraulic grab bucket GB mainly consists of two actions: a gripping action that transitions from state (1) to state (2) in Figure 2, and an opening action that transitions from state (2) to state (3). Occasionally, it may perform a mid-air closing action in which the grab bucket is closed while suspended in mid-air. During the closed-loop operation, the hydraulic cylinder CY supports the force that would cause the bucket shell (claw) CL to fall due to its own weight. However, since this closed-loop operation is not necessary for the bulk material transport cycle, the width of the grab bucket is reduced in order to move it closer to a wall or other object. This is a rare operation used in situations such as fence removal or maintenance. Even in this suspended operation, the load is stable, resulting in a stable operating time.

[0020] Figure 3 is a hydraulic circuit diagram of one embodiment using a hydraulic pump P with a variable discharge mechanism in a hydraulic grab bucket GB to which the present invention can be applied. Figure 4 is a hydraulic circuit diagram of one embodiment using a hydraulic pump P without a variable discharge mechanism. The present invention aims to remotely determine the state of the hydraulic circuit of a hydraulic grab bucket GB by monitoring the power supply of the hydraulic pump drive motor M, but the configuration of the circuit is not particularly limited. Furthermore, while this embodiment of the hydraulic circuit is a configuration in which the hydraulic pump P rotates unidirectionally and the oil passage is switched by an electromagnetic switching valve SV, in recent years hydraulic circuits in which the hydraulic pump P rotates bidirectionally and the electromagnetic switching valve SV is omitted have come into use. However, the same applies when applying the present invention to a bidirectional rotating hydraulic circuit configuration; it is not limited to unidirectional or bidirectional pumps.

[0021] In the hydraulic circuit of the embodiment shown in Figure 3 or Figure 4, when power is supplied to the hydraulic pump drive motor M, the hydraulic pump P rotates and pressurized oil is discharged. When the electromagnetic switching valve SV is in neutral, the pressurized oil discharged by the hydraulic pump P is returned to the oil tank OT and no pressure is generated. When a gripping or occluding operation CC is performed, the electromagnetic switching valve SV switches, and the pressurized oil generated by the hydraulic pump P is directed to the hydraulic cylinder head side HD, while the discharged oil from the hydraulic cylinder rod side RD is directed to the oil tank OT. This causes the hydraulic cylinder CY to operate in the bucket closing direction CF. Note that during the occluding operation CC, the hydraulic cylinder CY is pulled from the load side, so the throttling valve TH restricts the flow rate to prevent a negative pressure condition. When the opening operation OC is performed, the electromagnetic switching valve SV switches, and the pressurized oil generated by the hydraulic pump P is directed to the hydraulic cylinder rod side RD, while the discharged oil from the hydraulic cylinder head side HD is directed to the oil tank OT. As a result, the hydraulic cylinder CY operates in the bucket opening direction OF.

[0022] In the hydraulic circuit of the embodiment shown in Figure 3, when the closed end position CP is reached, or when the open end position OP is reached, or when the hydraulic pressure PS reaches 21 MPa (variable discharge mechanism setting value) near the end of the grip, the variable discharge mechanism built into the hydraulic pump P is activated, and the discharge volume VO of the hydraulic pump P is throttled to limit the pressure rise. Specifically, when the hydraulic pressure PS at the discharge section of the hydraulic pump P exceeds 21 MPa, the compensator CS opens, pressurized oil flows to the control piston PT, pushing the control piston PT in, and the discharge volume VO of the hydraulic pump P is throttled to limit the pressure rise. In the hydraulic circuit of the embodiment shown in Figure 3, a safety valve RV is equipped, but since the pressure limiting is performed by the variable discharge mechanism of the hydraulic pump P, the safety valve RV does not activate as long as the variable discharge mechanism of the hydraulic pump P is functioning normally.

[0023] In the hydraulic circuit of the embodiment shown in Figure 4, when the closed end position CP is reached, or when the open end position OP is reached, or when the gripping is near its end and the pump becomes restrained, the hydraulic pump P does not have a variable discharge mechanism. Therefore, the hydraulic pressure PS rises while the discharge amount is kept almost constant, and when the hydraulic pressure PS reaches 20 MPa (safety valve RV setting value), the safety valve RV opens, and hydraulic pressure PS is generated while oil flows through the safety valve RV, resulting in a large loss in this section.

[0024] The time chart shown in Figure 5 is a time chart for when the hydraulic circuit of the embodiment in Figure 3 is used. The time chart shown in Figure 6 is a time chart for when the hydraulic circuit of the embodiment in Figure 4 is used. The upper part of the time chart shows the operating state CO, and the changes in hydraulic pressure PS and discharge volume VO in the middle section are shown for the gripping operation GC, opening operation OC, and free-closing operation CC. The lower part shows the work amount WS for the changes in the upper and middle sections.

[0025] Regarding the operation state CO, the grab operation GC is performed with the hydraulic grab bucket GB resting on the bulk material TR and closed, while the suspended closing operation CC is performed with the hydraulic grab bucket GB suspended in mid-air and closed. The difference between the grab operation GC and the suspended closing operation CC is whether or not the hydraulic grab bucket GB is resting on the ground. Both are the same closing operation signal, and whether or not it is resting is determined by the detection value of the load cell LD. The open operation OC cannot be performed when the bucket is resting on the ground, so it is performed with the hydraulic grab bucket GB suspended in mid-air. These control signals may be provided by the controller during manual operation, or they may be output within the automatic control software during automatic control.

[0026] When a hydraulic grab bucket GB is placed on top of bulk material TR and closed (grabbing operation GC) is performed, the hydraulic pressure PS rises from approximately 8 MPa to the maximum pressure. Meanwhile, although the discharge volume decreases slightly with the increase in pressure, it continues to discharge at the specified discharge volume VO. In the case of the hydraulic pump P with a variable discharge mechanism shown in Figure 5, the discharge volume VO is throttled when the maximum pressure is reached, but it is gradually throttled as the grabbed material is compressed by the pressure, and when it reaches the closed end position CP, the discharge volume VO is throttled all at once, and the hydraulic pressure PS and discharge volume VO are shut off when the gripping operation GC is turned off. In contrast, in the case of the hydraulic pump P without a variable discharge mechanism shown in Figure 6, the discharge volume VO continues to be throttled even when the hydraulic pressure PS rises, a surge pressure is generated when the safety valve RV opens, and then the hydraulic pressure PS is maintained at the maximum pressure set by the safety valve, and the hydraulic pressure PS and discharge volume VO are shut off when the gripping operation GC is turned off.

[0027] When the opening operation OC is performed, a hydraulic pressure PS of approximately 6 MPa is generated, lifting the weight of the shell (claws) CL of the hydraulic grab bucket GB. As the opening progresses and the fulcrum lifting the bucket shell (claws) CL shifts, the hydraulic pressure PS gradually increases with the increase in load, rising to approximately 7 MPas. When the open end position OP is reached, the pressure rises to its maximum level, and in the case of the hydraulic pump P with a variable discharge mechanism shown in Figure 5, the discharge volume VO is suddenly throttled. At this time, a pressure surge occurs due to the throttling delay. When the hydraulic pressure PS is at its maximum and the discharge volume VO is at its minimum, the opening operation OC is turned off, shutting off the hydraulic pressure PS and discharge volume VO. In contrast, in the case of the hydraulic pump P without a variable discharge mechanism shown in Figure 6, even when the pressure rises to its maximum level when the open end position OP is reached, the discharge volume VO continues to discharge, a surge pressure is generated when the safety valve RV opens, and then the hydraulic pressure PS is maintained at the maximum pressure set by the safety valve, and the opening operation OC is turned off, shutting off the hydraulic pressure PS and discharge volume VO.

[0028] When a hydraulic grab bucket GB is closed (in-situ closure operation CC) without touching the bottom, the hydraulic pressure PS attempts to become negative due to the weight of the bucket shell (claw) CL. At this time, the throttle valve TH restricts the flow rate, and the pump operates to the closed end position CP with a small hydraulic pressure PS. As soon as the pump reaches the closed end position CP, the hydraulic pressure PS rises to its maximum pressure. Consequently, in the case of a hydraulic pump P with a variable discharge mechanism as shown in Figure 5, the discharge volume VO is suddenly throttled. At this time, a pressure surge occurs due to the throttling delay. When the hydraulic pressure PS reaches its maximum pressure and the discharge volume VO reaches its minimum, the open operation OC is turned off, shutting off the hydraulic pressure PS and discharge volume VO. In contrast, in the case of a hydraulic pump P without a variable discharge mechanism as shown in Figure 6, even if the pressure rises to the maximum pressure when it reaches the closed end position CP, the discharge volume VO continues to discharge, a surge pressure occurs when the safety valve RV opens, and then the hydraulic pressure PS is held at the maximum pressure set by the safety valve, and the close operation CC is turned off, shutting off the hydraulic pressure PS and discharge volume VO.

[0029] Here, the product of the hydraulic pressure PS and the discharge rate VO becomes the work rate WS. This work rate WS then becomes the load on the hydraulic pump drive motor M. Therefore, by monitoring the current or power value flowing from the control device CT to the hydraulic pump drive motor M, it is possible to determine if there is an abnormality in the hydraulic circuit. In the case of the hydraulic pump P with a variable discharge mechanism shown in Figure 5, when the closed end position CP or the open end position OP is reached, the discharge amount VO is reduced, and therefore the work amount WS, which is the product of the hydraulic pressure PS, is also reduced. In contrast, in the case of the hydraulic pump P without a variable discharge mechanism shown in Figure 6, when the closed end position CP or the open end position OP is reached, the work amount WS is reduced. When the valve reaches the open position OP, it generates hydraulic pressure PS while simultaneously flowing discharge volume VO through the safety valve RV. As a result, the work volume WS, which is the product of these two values, swings to a large value, causing excessive losses. Therefore, in the case of hydraulic pumps P that do not have a variable discharge mechanism, a larger hydraulic pump P is often used to take advantage of the low cost of the hydraulic pump P, thereby reducing the load factor and suppressing problems. This often results in a design that increases the discharge volume VO and lowers the hydraulic pressure PS. Conversely, in the case of hydraulic pumps P that have a variable discharge mechanism, a larger load factor is often used to increase the hydraulic pressure PS, and a smaller hydraulic pump P is used to maximize the capacity of the hydraulic pump P.

[0030] When monitoring the current or power value flowing through the hydraulic pump drive motor M to determine abnormalities in the hydraulic circuit, if monitoring the current value, instead of using the measured current value directly, the measured current value is decomposed into vectors, the magnetic flux current component is removed, and only the torque current component is extracted. By determining the state of the hydraulic circuit based on the magnitude of the torque current, an accurate determination can be made. Some inverter control devices output the torque current value as a torque value, and the current value described in this invention is a general term that includes these torque current values ​​and torque values ​​based on torque current values. Furthermore, monitoring the power value of the hydraulic pump drive motor M, rather than monitoring the current value, can further improve the accuracy of status determination compared to monitoring the current value.

[0031] As shown in Figure 7, in the case of a hydraulic pump P with a variable discharge mechanism, when it reaches the closed end position CP or the open end position OP, the discharge amount of the hydraulic pump P is reduced, and the load on the hydraulic pump drive motor M decreases, so a small value of power (current) WV at the time of discharge cutoff is detected. In this way, the power value or current value of the power supply of the hydraulic pump drive motor M is monitored, and when a small value of power (current) WV at the time of discharge cutoff is detected, it can be determined that the closed end position CP or the open end position OP has been reached. Patent Document 1 describes a technique for determining when the closed end position CP or open end position OP has been reached based on the peak value. However, when the load factor of the hydraulic pump P is high, it is difficult to detect the peak value when the closed end position CP is reached. Nevertheless, it is possible to detect the power (current) WV at the time of discharge cutoff, which is always a small value, after the closed end position CP or open end position OP has been reached. Therefore, even when the load factor of the hydraulic pump P is high, the closed end position CP or open end position OP can be reliably detected.

[0032] By the way, in the case of a hydraulic pump P having a variable discharge mechanism as shown in Figure 7, if an abnormality occurs in the variable discharge mechanism of the hydraulic pump P, it becomes impossible to determine that the closed end position CP or the open end position OP has been reached. Moreover, various peripheral devices that were protected by the performance of the variable discharge mechanism may be damaged, resulting in secondary problems. To prevent this problem, the system monitors the consistency between the power value or current value of the power supply for the hydraulic pump drive motor M and the elapsed time to detect any abnormalities.

[0033] As a method for determining whether the variable discharge mechanism of the hydraulic pump P is functioning correctly, when an opening operation OC is performed and the opening operation time TO has elapsed, or when a partial closing operation CC is performed and the partial closing operation time TC has elapsed, it is possible to determine whether the power value or current value of the power supply for the hydraulic pump drive motor M at that time is within a certain range corresponding to the power (current) WV at the time of discharge interruption.

[0034] Similarly, in the case of a hydraulic pump P that does not have a variable discharge mechanism as shown in Figure 8, when an opening operation OC is performed and the opening operation time TO has elapsed, or when a partial closing operation CC is performed and the partial closing operation time TC has elapsed, it is determined whether the setting value of the safety valve RV has changed by checking whether the power value or current value of the power supply for the hydraulic pump drive motor M at that time is within a certain range corresponding to the power (current) WB when the safety valve is activated. Generally, the setting value of the safety valve RV decreases each time the safety valve RV is activated. This tends to decrease, and if the value of the safety valve RV drops, it becomes impossible to generate gripping pressure. Also, if the value of the power (current) WB when the safety valve is activated is used to determine whether the closed position CP or open position OP has been reached, then detection will become impossible. If it is determined that the closed position CP or open position OP has not been reached and the safety valve RV remains activated, operation will continue, causing the hydraulic fluid temperature to rise abnormally, leading to various secondary malfunctions. Therefore, this detection is important.

[0035] Here, in Figure 7 or Figure 8, the load during the opening operation OC and the closing operation CC of the hydraulic grab bucket GB is constant. Therefore, the opening operation time TO and the closing operation time TC are determined solely by the discharge rate VO of the hydraulic pump P relative to the volume of the hydraulic cylinder CY. However, for the gripping operation GC, the discharge rate may change depending on the density and unevenness of the bulk material TR being gripped, or the bucket shell (claws) CL may become full during the gripping operation, causing it to stop before reaching the closed end position CP. Thus, the gripping operation time TG is not constant. Therefore, during the gripping operation GC, it is necessary to consider the time margin and determine whether it corresponds to the power (current) WV at the time of discharge cutoff or the power (current) WB at the time of safety valve operation. Consequently, the detection during the gripping operation GC can only be used as a reference value, so caution is required.

[0036] In the hydraulic system of the hydraulic pump P having a variable discharge mechanism as shown in Figure 7, the time from the start of the opening operation OC or the closing operation CC until the power (current) WV at the time of discharge cutoff falls within the specified range is measured to determine whether there is an abnormality by checking whether the time has increased or decreased from within the specified time. Similarly, in the case of the hydraulic pump P without a variable discharge mechanism as shown in Figure 8, the time from the start of the opening operation OC or the closing operation CC until the power (current) WB at the time of safety valve operation falls within the specified range is measured to determine whether there is an abnormality by checking whether the time has increased or decreased from within the specified time. If the resistance of the oil passage increases due to some factor, the discharge volume VO of the hydraulic pump P decreases, and the operating time increases. Factors that increase resistance in the oil passages include clogging of the suction filter SF and return filter RF, deterioration of the hydraulic fluid, misalignment of the throttle valve TH's setting value, narrowing of the oil passages in valves, and deterioration of the hydraulic pump P which leads to increased leakage and reduced discharge volume. However, clogging of the suction filter SF and return filter RF, which require cleaning or replacement as part of regular maintenance, is a highly likely factor, so a filter clogging indicator will be triggered. Furthermore, since the time for GC during a grab operation varies depending on the load conditions, the threshold for the abnormality detection time for the grab operation time TG must have sufficient margin to prevent false detections, and detection during grab operations can only be used as a reference.

[0037] Furthermore, the open power (current) WO or closed power (current) during the open operation OC or closed operation CC is measured and compared with the reference value to check for any abnormalities. During gripping operations with a circuit generator (GC), the load fluctuates significantly due to the state of the individual transistors (TRs). Therefore, the power (current) WG during gripping is difficult to use to determine abnormalities unless there is a critical failure, and can only be used as a reference value. Furthermore, when detecting an open operation OC, it is preferable to measure the open power (current) WO after dropping the grasped bulk material TR. Comparing the open power (current) WO slightly before detecting the open end position OP with a reference value allows for more accurate abnormality detection.

[0038] Incidentally, a commonly used method for detecting the closed end position CP or open end position OP is one that utilizes the fact that the pressure in the hydraulic circuit rises when the operation is mechanically locked at the closed end position CP or open end position OP, and detects the closed end position CP or open end position OP using a pressure switch SW installed in the hydraulic circuit. However, the method of detecting the closed end position CP or open end position OP by confirming that the power (current) WV at the time of discharge interruption falls within a specified range for the throttle function operation state, as described in the present invention, can be replaced with the conventional method of detection using a pressure switch SW. By using both methods in combination and performing mutual checks, it is also possible to improve reliability.

[0039] Detection using a pressure switch SW occurs when the pressurized oil, which is generating a flow, becomes mechanically locked in the closed position CP or open position OP. This triggers a high hydraulic surge during the operating delay time of the variable discharge function of the hydraulic pump P or the safety valve RV. The detection method using a pressure switch SW can capture this high surge pressure, thus reliably detecting the mechanically locked state at the closed position CP or open position OP. However, since this surge pressure value is not reflected in the power (current) value of the hydraulic pump drive motor M, in loads where the maximum pressure is reached at the end of gripping, such as during gripping, and the variable discharge mechanism is activated, it is difficult to detect the surge pressure when the power (current) value of the hydraulic pump drive motor M rises. The variable discharge function is activated after the operation is mechanically locked at the closed end position CP or open end position OP, and the closed end position CP or open end position OP can be reliably detected by sensing that the load on the hydraulic pump drive motor M has decreased.

[0040] Incidentally, the specific method for using the pressure switch SW in conjunction with the hydraulic pump involves detecting when the closed end position CP or open end position OP has been reached by the pressure switch SW, then measuring the power (current) WV of the hydraulic pump drive motor M at the time of discharge interruption, checking whether the value is within the specified range, and confirming whether the variable mechanism of the hydraulic pump P is functioning correctly. Furthermore, the system detects the time from the start of operation of the hydraulic grab bucket GB until the pressure switch SW detects that it has reached the closed end position CP or the open end position OP, thereby detecting an increase or decrease in oil passage resistance, such as filter clogging or a change in the throttle valve setting value. Furthermore, the system determines whether the power (current) before detection of the pressure switch SW reaching the closed end position CP or the open end position OP is within the specified range, thereby determining the integrity of the hydraulic circuit. These details are similar to the method described earlier for detecting the arrival of the closed-end position CP or open-end position OP using power (current), and are intended to complement or improve accuracy.

[0041] The remote monitoring system for a hydraulic grab bucket of the present invention has been described based on an embodiment, but the present invention is not limited to the configuration described in the above embodiment, and its configuration can be modified as appropriate without departing from the spirit of the invention. [Industrial applicability]

[0042] According to the remote monitoring system for hydraulic grab buckets of the present invention, the condition of the hydraulic grab bucket can be monitored while it is in operation, improving the reliability of the hydraulic grab bucket and offering significant potential for industrial applications. [Explanation of Symbols]

[0043] CR Crane WR Wire Rope GB Grab Bucket LD load meter CA Bucket Power Cable OU Hydraulic Unit TR loose parts WL Crane Wiring Cable OM Crane Operator CT control device CL Bucket Shell (Tines) CY Hydraulic Cylinder CF bucket closing direction OF Bucket opening direction M Hydraulic pump drive motor P Hydraulic pump PT Control Piston CS Compensator SV Solenoid Switching Valve RV safety valve CH check valve TH throttle valve SW pressure switch OT Oil Tank SF Suction Cycle RF return filter HD Hydraulic Cylinder Head Side RD Hydraulic Cylinder Rod Side CO operating status GC grasp operation OC open operation CC midair closure operation PS Hydraulic VO discharge amount t time CP closed end position OP Open end position WS workload TG Grasping Action Time TO opening operation time TC midair closing operation time WV Power (current) at the time of discharge interruption WG Power (current) when gripping Power (current) when WO is open Power (current) when the WC is closed in space Power (current) when the WB safety valve is activated.

Claims

1. A hydraulic grab bucket remote monitoring system for a hydraulic grab bucket, which uses a hydraulic system for a hydraulic grab bucket, wherein the hydraulic pump used in the hydraulic system is equipped with a variable discharge mechanism to suppress the discharge amount, or the hydraulic pump does not have a variable discharge mechanism inside and is equipped with a safety valve outside that returns the pressurized oil generated by the hydraulic pump to the hydraulic oil tank, and observes from the power supply side of the motor that drives the hydraulic pump when the grab bucket reaches the open end position or closed end position and reaches the mechanical limit of movement, and observes from the power supply side of the motor that drives the hydraulic pump that the current value or power value of the motor driving the hydraulic pump decreases in the hydraulic system using a hydraulic pump equipped with a variable discharge mechanism, and increases in the hydraulic system using a hydraulic pump without a variable discharge mechanism, and monitors the normal operating state of the hydraulic grab bucket based on this information.

2. A remote monitoring system for a hydraulic grab bucket according to claim 1, in a hydraulic system in which a variable discharge mechanism for suppressing the discharge amount is provided inside the hydraulic pump used in the hydraulic system, wherein when the grab bucket reaches the open end position or the closed end position and reaches the mechanical limit of movement, the variable mechanism for suppressing the discharge amount of the hydraulic pump is activated, and the load on the pump has decreased, which is detected by a change in the current value or power value of the motor driving the pump to a small value, and it is determined that the grab bucket has reached the open end position or the closed end position.

3. A remote monitoring system for a hydraulic grab bucket according to claim 1, wherein, when operating a hydraulic grab bucket, after a specified time has elapsed for each grab bucket to reach the open or closed end position, the system measures the current value or power value of the motor driving the hydraulic pump, confirms that the current value or power value is within a specified range corresponding to the load when the hydraulic pump reaches its mechanical limit, and determines that it is functioning normally.

4. A remote monitoring system for a hydraulic grab bucket according to claim 1, which measures the time from when operation of the hydraulic grab bucket is started until it is detected that the current value or power value of the hydraulic pump drive motor is the current value or power value that indicates the mechanical limit of movement at the closed end position or open end position, and confirms that the time is within a specified range and determines that it is normal.

5. A remote monitoring system for a hydraulic grab bucket according to claim 1, wherein when a hydraulic grab bucket is opened or closed without touching the bottom, the system starts measuring and recording the current or power value of the hydraulic pump drive motor after the operation has begun, and then, when a current or power value indicating the open or closed position is detected, if the current or power value recorded before the detection falls within a specified range, the system determines that the system is functioning normally.

6. A remote monitoring system for a hydraulic grab bucket according to any one of claims 1 to 5, wherein the reliability of both signals is improved by using in combination a signal detected by a pressure switch when the hydraulic circuit pressure rises, and a signal detected when the amount of increase or decrease in the current value or power value of the motor driving the hydraulic pump falls within a specified range, as a signal indicating that the hydraulic grab bucket has reached the open or closed end position.

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