Crane and control method thereof

Abstract

To provide a crane and its control method capable of reducing a load by a generated overload by more quickly stopping a winding device when the overload is generated.SOLUTION: A crane 1 including a winding device 2, wire ropes 3, a hoisting accessory 4, a load measurement device 5, and a calculation device 6 includes a storage unit 15 in which a speed limit Va set to a speed of 30% or less of a rated value of a winding speed of the winding device 2 is stored. when a container Ca is lifted by the winding device 2, the load measurement device 5 acquires a load datum D1. The operation device 6 executes data-processing for determining the completion of lifting of the container Ca from the ground based on the load datum D1, and control for limiting the winding speed to the limit speed Va until the lifting of the container Ca from the ground is completed, and releasing the limit to the winding speed when the lifting of the container Ca from the ground is completed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a crane and a control method thereof, and more particularly to a crane and a control method thereof that can more quickly stop a winding device when an overload occurs, thereby reducing the load caused by the overload that has occurred. [Background technology]

[0002] Containers stored in the holds or on the upper decks of container ships are secured with lashing devices such as lashing rods and stacking cones to prevent the cargo from shifting. When an attempt is made to lift a container that has not yet been released from its lashing devices, an overload (snag load) occurs. This overload places a significant strain on the reeling device and the crane equipped with the reeling device. Therefore, it is essential for cranes to take measures to prevent overloads from occurring.

[0003] A hoist for a crane has been proposed that stops its hoisting operation when an overload condition is identified (see Patent Document 1). In the invention described in Patent Document 1, the time required from when the hoisting operation of the hoist is prohibited until the hoisting operation actually stops depends on the hoisting speed at the time the hoisting operation is prohibited. Therefore, the faster the hoisting speed, the longer the hoisting operation continues in an overload condition, and the load on the hoist and the crane equipped with the hoisting machine increases accordingly. Therefore, there is room for improvement in how to more quickly stop the winding device when an overload occurs and reduce the load caused by the overload. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-11165 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a crane and a control method thereof that can more quickly stop a winding device when an overload occurs, thereby reducing the load caused by the overload that has occurred. [Means for solving the problem]

[0006] The crane of the present invention, which achieves the above-mentioned object, is equipped with a winding device that winds in / out a wire rope connected to a hoisting device, a load measuring device that acquires load data showing changes in the load value acting on the wire rope over time, and a computing device that processes the load data, and is characterized in that it has a memory unit that stores a speed limit set to a speed that is 30% or less of the rated value of the winding speed of the winding device, and when the winding device winds in the wire rope and lifts a load attached to the hoisting device, the computing device performs data processing to determine completion of lifting of the load based on the load data, and controls to limit the winding speed of the winding device to the speed limit until the load is lifted from the ground, and to release the limit on the winding speed to the speed limit when the load is lifted from the ground.

[0007] The crane control method of the present invention is a method for controlling a crane that winds up a wire rope using a winding device and lifts a load using a sling connected to the wire rope, and is characterized in that when lifting the load, a speed limit is set to 30% or less of the rated winding speed of the winding device, winding of the wire rope by the winding device is started at this speed limit, load data showing changes in the load value acting on the wire rope over time is obtained using a load measuring device, the obtained load data is processed by a computing device to determine whether the load has been lifted from the ground, and when the load has been lifted from the ground, the load is lifted at a predetermined winding speed. [Effects of the Invention]

[0008] According to the present invention, when lifting a load, the winding speed of the winding device is limited to the limited speed until the load is lifted from the ground. The time required to stop the winding device with such a limit is only the time it takes to reduce the winding speed from the limited speed to zero, so the winding device can be stopped more quickly when an overload occurs. As a result, the load on the winding device and the crane caused by the overload can be reduced. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an explanatory diagram illustrating a state at the start of lifting in an embodiment of a crane. [Figure 2] FIG. 10 is an explanatory diagram illustrating a state in which the lifting tool of the embodiment of the crane is lifted from the ground. [Figure 3] FIG. 10 is an explanatory diagram illustrating a state in which one side of a container in an embodiment of a crane is lifted off the ground. [Figure 4] FIG. 10 is an explanatory diagram illustrating a state in which the container of the embodiment of the crane has been lifted off the ground. [Figure 5] 10 is a graph illustrating load data. [Figure 6] FIG. 1 is a flow chart illustrating the procedure of a crane control method. [Figure 7] 6 is a graph showing an enlarged portion of the load data in FIG. 5. [Figure 8] 1 is an explanatory diagram illustrating each step in the operation of lifting a container by a crane. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a crane and a control method thereof according to the present invention will be described based on an embodiment shown in the drawings.

[0011] The embodiment of the crane 1 illustrated in Figures 1 to 4 is operated at a container terminal and handles containers Ca and Cb as cargo. Using this crane 1, the crane control method illustrated in Figure 6 is carried out.

[0012] This control method is performed when the reeling device 2 reels in each of the wire ropes 3a (3b), 3c (3d) (hereinafter referred to as each wire rope 3) and lifts the container Ca using the slings 4 connected to each of the wire ropes 3. In the procedure of this control method, the calculation device 6 executes control to limit the reeling speed of the reeling device 2 to a speed limit Va, and the reeling device 2 starts reeling in each of the wire ropes 3 at the speed limit Va (S110). Next, the load measuring device 5 acquires load data D1 and D2 illustrated in FIG. 5 (S120). Next, the calculation device 6 processes the load data D1 and D2 to determine whether the container Ca has been lifted from the ground (S130). Then, when the container Ca has been lifted from the ground, the calculation device 6 executes control to release the restriction of the reeling speed to the speed limit Va, and the container Ca is reeled in at a command value (a preset reeling speed), and the container Ca is lifted (S150).

[0013] 1 to 4 show the various states in sequence during the process in which the reeling device 2 reels in each wire rope 3 and lifts container Ca with the hoisting device 4. Specifically, FIG. 1 shows the state immediately after lifting begins, FIG. 2 shows the state after the hoisting device 4 has been lifted from the ground, FIG. 3 shows the state after one side of container Ca has been lifted from the ground, and FIG. 4 shows the state after container Ca has been lifted from the ground. The state after the hoisting device 4 has been lifted from the ground is a state in which the hoisting device 4 and the top surface of container Ca are separated, and only the weight of the hoisting device 4 acts on each wire rope 3. The state after container Ca has been lifted from the ground is a state in which the bottom surface of container Ca and the top surface of container Cb are completely separated.

[0014] Various known cranes such as a gantry crane or a transfer crane can be used as the crane 1. The crane 1 is not limited to cranes operated in container terminals, but may also be an overhead crane, a bucket unloader, a jib crane, a stacker crane, or the like. The crane 1 of the embodiment is, for example, a monobox gantry crane.

[0015] This crane 1 travels in the depth direction of the page on a traveling device (not shown), a trolley 8 moves laterally in the left-right direction of the page along girders 7 such as girders or booms, and containers are handled by a reeling device 2 reeling in each wire rope 3 to raise the hoisting device 4, and a reeling device 2 letting out each wire rope 3 to lower the hoisting device 4. Containers Ca and Cb, which are on the upper deck UD of a container ship, are connected and secured to container Cb, and container Cb is connected and secured to the upper deck UD, respectively, by a securing device LD such as a stacking cone.

[0016] The crane 1 is equipped with a winding device 2, wire ropes 3, a hoisting device 4, a load measuring device 5, and a computing device 6. The hoisting device 4 has four sets of flippers 9, twist locks 10, twist lock sensors 11, and floor landing sensors 12, one set of which is located at each of the four corners when viewed from above (viewed from below).

[0017] The reeling device 2 can be installed in any location depending on the specifications of the crane 1. In this embodiment, the reeling device 2 is installed in a machine room 13 installed on the girder 7. This reeling device 2 has drums that reel in each wire rope 3, a motor that rotates and drives the drum, an inverter that controls the motor speed, a brake that stops the drum rotation, and the like. The number of reeling devices 2 is not limited to one, and multiple reeling devices 2 may be provided for one hoisting device 4, and one reeling device 2 may be configured to drive multiple drums with a single motor and inverter. The reeling device 2 also has a sensor that detects the length of each wire rope 3 that has been reeled in or reeled out.

[0018] One end of each wire rope 3 is fixed to the reeling device 2, the other end is fixed to the girder 7 or trolley 8, and the intermediate portion between the two ends is connected to the hoisting device 4 via a sheave. The number and hanging method of each wire rope 3 can be selected as desired depending on the specifications of the crane 1 and the hoisting device 4. In this embodiment, for example, there are four wire ropes 3. Two wire ropes 3a and 3b overlap in the depth direction of the page, with wire rope 3a facing the front and wire rope 3b facing the rear. The intermediate portion of wire rope 3a (3b) is connected to the hoisting device 4 via a sheave on the left side of the page (land side). The other end of wire rope 3a (3b) is fixed to a double-rod cylinder 14a fixed to one end of the girder 7 (one end of the boom) extending to the right side of the page (sea side). That is, the other ends of wire rope 3a and wire rope 3b are connected to each other via the double-rod cylinder 14a. Similarly, the remaining two wire ropes 3c and 3d are stacked in the depth direction of the paper, with wire rope 3c on the front side of the paper and wire rope 3d on the back side of the paper. The middle part of wire rope 3c (3d) is connected to hoisting tool 4 via a sheave on the right side of the paper (sea side), and the other end is fixed to double-rod cylinder 14b.

[0019] Various known hoisting devices such as hooks and spreaders can be used as the hoisting device 4 depending on the specifications of the cargo to be handled. When the cargo to be handled is a container, the hoisting device 4 is, for example, a spreader that can lift various containers such as 20-foot containers and 40-foot containers. This spreader can, for example, lift two 20-foot containers or one 40-foot container at the same time.

[0020] The flippers 9, twist locks 10, twist lock sensors 11, and landing sensors 12 can be devices that are standardly installed on known spreaders. The flippers 9 are used to align the hoisting fixtures 4 with the containers Ca and Cb. The twist locks 10 are used to connect the hoisting fixtures 4 with the containers Ca and Cb. The twist lock sensors 11 detect the connection and release of the connection between the hoisting fixtures 4 and the containers Ca and Cb by the twist locks 10. The landing sensor 12 detects the landing of the hoisting fixtures 4 on the containers Ca and Cb and the landing of the containers Ca and Cb hoisted by the hoisting fixtures 4 on the upper deck UD, etc.

[0021] The load measuring device 5 measures the load value acting on each wire rope 3 at a predetermined cycle. Various known load meters such as load cells can be used for this load measuring device 5. The load values ​​measured by the load measuring device 5 are transmitted to the calculation device 6 and stored in the memory unit 15 of the calculation device 6 as load data D1 and D2 indicating changes in the load values ​​over time.

[0022] The predetermined period can be set arbitrarily, but is preferably greater than 0 ms and less than or equal to 30 ms, and more preferably greater than or equal to 15 ms and less than or equal to 25 ms. A smaller predetermined period is more advantageous for identifying finer fluctuations in the load value, but the amount of data D1 and D2 increases, and a larger predetermined period is more advantageous for reducing the amount of data D1 and D2.

[0023] The location for installing this load measuring device 5 can be selected arbitrarily so that the load acting on each wire rope 3 can be measured, but it is preferable to install it at the dead rope portion of each wire rope 3 (a portion that does not move in the extension direction of each wire rope 3). The load measuring device 5 of this embodiment is installed at the connection portion between each of the double rod cylinders 14a, 14b and each of the wire ropes 3, and measures the tension acting on each of one set of wire ropes 3a (3b) and one set of wire ropes 3c (3d) as a load value.

[0024] An appropriate number of these load measuring devices 5 may be installed depending on the number of wire ropes 3 and how they are hung. The load measuring device 5 of the embodiment individually measures the load values ​​acting on each of a set of wire ropes 3a (3b) connected to the left side (land side) of the hoisting device 4 and a set of wire ropes 3c (3d) connected to the right side (sea side) in the left-right direction of the page (lateral direction of the trolley 8) when viewed in the depth direction of the page (travel direction of the crane 1). Note that the load measuring device 5 may also be capable of individually measuring the load values ​​acting on each of the front and back sides of the hoisting device 4 in the depth direction of the page when viewed in the left-right direction of the page.

[0025] The load data D1 and D2 shown in Fig. 5 are acquired by the load measuring device 5 and stored in the auxiliary memory of the calculation device 6 as the memory unit 15. In this graph, the horizontal axis represents time [s] and the vertical axis represents load value [N], with the solid line representing load data D1 of the change over time in the load value acting on one set of wire ropes 3a (3b) and the dashed line representing load data D2 of the change over time in the load value acting on one set of wire ropes 3c (3d). The difference between the fluctuation in the load value represented by the solid line and the fluctuation in the load value represented by the dashed line is due to factors such as the uneven load on the container Ca.

[0026] Time t0 indicates the time when lifting begins, i.e., the time when winding of each wire rope 3 by the reeling device 2 begins. Time t1 indicates the time when the landing sensor 12 detects that the hoisting tool 4 has not yet landed, i.e., the time when the hoisting tool 4 has been lifted off the ground. Time t2 indicates the time when it is visually confirmed that only one side of the container Ca lifted by the hoisting tool 4 has been lifted off the ground. Time t3 indicates the time when it is visually confirmed that the container Ca has been lifted off the ground.

[0027] Time t4 indicates the time when a local maximum point P1 due to one side of container Ca being lifted off the ground is detected in the load data D1. This local maximum point P1 is caused by the inertial force of one side of container Ca being directed upward due to the lifting of one side of container Ca at time t2, resulting in the release of tension in the wire ropes 3a (3b). Time t5 indicates the time when a local maximum point P3 due to the completion of lifting of container Ca is detected in the load data D2. Note that around time t5, a local maximum point P2 due to the completion of lifting of container Ca is detected in the load data D1, and a local maximum point P3 due to the completion of lifting of container Ca is detected in the load data D2. The local maximum points P2 and P3 are caused by the completion of lifting of container Ca at time t3, when the bottom surface of container Ca and the top surface of container Cb are completely separated, the overall inertial force of container Ca is directed upward, and the tension in each wire rope 3 is released. The difference in time between visual confirmation of ground clearance and detection of the maximum point is caused by the delay time required for the load measuring device 5 to acquire the fluctuation in the load value acting on the wire rope 3.

[0028] The judgment value Na in Fig. 5 is set to a value that allows for determining whether an overload has occurred. This judgment value Na is, for example, about 300 kN. When the load value becomes equal to or greater than the judgment value Na, the calculation device 6 executes control to stop the winding of each wire rope 3 by the winding device 2.

[0029] The arithmetic device 6 is configured as a computer, and various data are input and stored therein, and this data is used to process data and control the winding device 2. Various known computers can be used as the arithmetic device 6. The arithmetic device 6 has a processing unit (CPU), a main storage unit (memory), and an auxiliary storage unit (e.g., HDD). The auxiliary storage unit corresponds to the storage unit 15 in which the speed limit Va is stored. There may be multiple arithmetic devices 6, and the multiple arithmetic devices 6 may individually perform different data processing and control.

[0030] The speed limit Va can be set to any positive speed up to 30% of the rated value (rated speed) of the winding speed of the winding device 2, but a speed within the range of 10% to 20% of the rated value is more preferable. The slower the speed limit Va, the longer the time required for winding, and the faster the speed limit Va, the longer the time required to stop the winding device 2 when an overload occurs.

[0031] Next, the procedure of an embodiment of the crane control method illustrated in Fig. 6 will be described. In this procedure, first, the calculation device 6 limits the winding speed of the winding device 2 to a speed limit Va, and the winding device 2 starts winding each wire rope 3 at the speed limit Va (S110). Next, the load measuring device 5 acquires load data D1 and D2 (S120). Next, the calculation device 6 continues to limit the winding speed to the speed limit Va (S140) until it is determined that the container Ca has been lifted from the ground based on the load data D1 and D2 (until S130: YES). When it is determined that the container Ca has been lifted from the ground (S130: YES), the limit on the winding speed is released (S150). That is, when the container Ca has been lifted from the ground, the container Ca is lifted at a preset winding speed (command value). This control method is a limited method for winding up the wire ropes 3 with the winding device 2 and lifting up the containers Ca and Cb connected to the hoisting devices 4. Each step (S110 to S150) will be described in detail below.

[0032] In step S110, the arithmetic device 6 executes data processing to limit the winding speed of the winding device 2 to the speed limit Va. When starting to lift the container Ca, a command value is input as a winding speed that is preset by operating the operating device or by the arithmetic device 6, and the winding device 2 attempts to wind each wire rope 3 at a winding speed according to the input command value. At this time, by executing this step S110, the winding speed of the winding device 2 is limited to the speed limit Va regardless of the input command value, and the winding of each wire rope 3 by the winding device 2 begins at the speed limit Va. The restriction on the winding speed to the speed limit Va is maintained until it is released in step S150, which will be described later.

[0033] In step S120, load data D1 and D2 are acquired by the load measuring device 5. Load values ​​measured by the load measuring device 5 are added to the load data D1 and D2 at predetermined intervals. The load data D1 and D2 may include all load values ​​from the start to the end of winding of each wire rope 3 by the winding device 2, but only need to include the number of load values ​​necessary for data processing in step S130, which will be described later. The required number is, for example, 5 to 15. Therefore, the load data D1 and D2 always include 5 to 15 load values, with the load values ​​measured by the load measuring device 5 being added at predetermined intervals and the oldest load value being deleted. In FIG. 6, a predetermined interval has elapsed when the process returns from step S140 to step S120.

[0034] In step S130, the calculation device 6 executes data processing to determine whether the container Ca has been lifted off the ground based on the load data D1 and D2. The state in which the container Ca has been lifted off the ground means the state in which the bottom surface of the container Ca and the top surface of the container Cb are completely separated, as illustrated in FIG. 4 above, and differs from the state in which only one side of the container Ca has been lifted off the ground, as illustrated in FIG. 3. If the calculation device 6 determines through data processing that the container Ca has not been lifted off the ground (S130: NO), the process proceeds to step S140, and if the calculation device 6 determines that the container Ca has been lifted off the ground (S130: YES), the process proceeds to step S150.

[0035] Those who manufacture and develop crane 1 or operate container terminals have accumulated vast amounts of data equivalent to the load data D1 and D2, such as data obtained during the manufacturing and development process and during operation, and the results of computer simulations. By analyzing this data, it is possible to determine that the container Ca has been lifted off the ground based on fluctuations in the load values ​​in the load data D1 and D2. In step S130, such knowledge can be used to determine that the container Ca has been lifted off the ground. In step S130, a prediction model may be generated by machine learning using the accumulated data, and the load data D1 and D2 may be input into the prediction model to predict the timing at which the container Ca has been lifted off the ground.

[0036] In step S130 of this embodiment, the lifting of container Ca is deemed to be completed when the cargo handling data D2 to be judged satisfies the following set condition: When there are multiple load data, the load data indicating the fluctuation of the load value of the wire rope connected to the side of container Cb that was in contact with container Ca until just before the lifting of container Ca was completed can be selected from the multiple load data as the load data to be judged. In the above-mentioned Figure 5, the load data D2 of the wire rope 3c (3d) connected to the side that was in contact with container Cb until just before the lifting of container Ca was completed, i.e., the side opposite to the side of container Ca that was previously lifted, is selected as the load data to be judged.

[0037] To select a judgment target from a plurality of load data, load data in which a maximum point has been detected from the plurality of load data is excluded from the candidates for the judgment target, and the last remaining load data is selected as the judgment target. For example, when a maximum point P1 is detected, load data D1 is excluded from the candidates for the judgment target. Next, the last remaining load data D2 is selected as the judgment target. To select a judgment target from a plurality of load data, when a maximum point is detected, the load data showing the largest load value among the plurality of load data is selected as the judgment target. For example, when maximum points P1 to P3 are detected, the load value of load data D2 is larger than the load value of load data D1 at each time. Therefore, load data D2 is selected as the judgment target.

[0038] To describe the conditions in more detail, in step S130 of the embodiment, the detection of the maximum point P3 in the load data D2 is deemed to be the completion of the lifting of the container Ca. Furthermore, in step S130, if the time elapsed from the completion of the lifting of the sling 4 to the detection of the maximum point P3 is less than a predetermined threshold value Δt, the lifting of the container Ca is deemed not to be complete. Generally, in step S130, the lifting of the container Ca is deemed to be complete when two conditions are met: the time elapsed from the completion of the lifting of the sling 4 is equal to or greater than the threshold value Δt, and the maximum point P3 is detected. For example, if the time from time t2, when the lifting of the sling 4 is completed, to time t5, when the maximum point P3 is detected, is less than the threshold value Δt, the lifting of the container Ca is deemed to be complete when a time equal to or greater than the threshold value Δt has elapsed since time t2. Furthermore, when the local maximum point P3 is detected after a time equal to or greater than the threshold value Δt has elapsed since time t2, it is deemed that the lifting of the container Ca has been completed. Furthermore, if the two conditions that the time elapsed since the lifting of the hoisting device 4 was completed is equal to or greater than the threshold value Δt and the local maximum point P3 is detected are not met, the lifting of the container Ca is deemed to have been completed when the condition that the length of each wire rope 3 wound by the reeling device 2 is equal to or greater than the preset threshold length ΔL is met.

[0039] To detect the local maximum point P3, it is necessary to determine the fluctuation of the load value in the period before and after time t5. The period for determining whether the local maximum point P3 has been detected in the load data D2 can be selected arbitrarily, but for example, it may be a period that includes at least about five measurement periods of the load measuring device 5 both before and after the time when the local maximum point occurred. For example, the determination of whether the local maximum point P3 has occurred is made after at least five periods have elapsed since time t5 when the local maximum point P3 occurred. In this way, the detection of the local maximum point P3 in the load data D2 is reliably determined at a timing that is later than the actual time t3 when the container Ca lifts off the ground.

[0040] The load data D1 and D2 are significantly affected by noise. Therefore, the load data D1 and D2 may contain local maximum points of load values ​​caused by noise other than the local maximum point P3. Therefore, in step S130, if 60% or more of 5 to 15 consecutive load values ​​immediately after the load value of the local maximum point is detected are less than the load value of the local maximum point, the local maximum point may be regarded as a local maximum point caused by ground breaking. In the embodiment, it is determined whether 7 or more (70% or more) of 10 consecutive load values ​​immediately after the load value of the local maximum point is detected are less than the load value of the local maximum point.

[0041] FIG. 7 shows the load data D2 illustrated in FIG. 5 from time t3 onward. In FIG. 7, the load value acting on the wire rope 3c (3d) increases until time t5, when the maximum point P3 occurs, and then decreases from time t5. The thin dashed lines indicating times t6 to t15 in FIG. 7 indicate the cycles at which the load measuring device 5 measures the load value. Since all of the 10 consecutive load values ​​immediately after detecting the load value of the maximum point P3 are less than the load value N3 of the maximum point P3, this maximum point P3 is considered to be a maximum point caused by the container Ca lifting off the ground. In this way, clearly distinguishing between a maximum point caused by noise and a maximum point P3 caused by the container Ca lifting off the ground is advantageous for more accurately identifying the state in which the container Ca has been lifted off the ground.

[0042] The threshold value Δt is set to a representative value (such as the average value, mode, or maximum value) of the period required from the completion of lifting of the hoisting gear 4 to the completion of lifting of the container Ca when the reeling speed of the reeling device 2 is limited to the speed limit Va, measured multiple times while changing the weight of the container Ca. While it is desirable to use the average or mode value as the representative value, using the maximum value makes it possible to more reliably determine the completion of lifting. If the period elapsed from the completion of lifting of the hoisting gear 4 to the occurrence of the local maximum point P3 is less than the threshold value Δt, it is determined that the lifting of the container Ca has not been completed. This threshold value Δt is, for example, greater than or equal to 1.0 seconds and less than or equal to 2.0 seconds.

[0043] The threshold length ΔL is set to a length greater than the maximum length of each wire rope 3 that can be wound by the winding device 2 in a situation where an overload occurs. This maximum length is the maximum value of the length of each wire rope 3 that can be wound by the winding device 2 in a state where an overload occurs (a state where the container Ca cannot be lifted). The threshold length ΔL is set based on data accumulated by the manufacturer and developer of the crane 1 or the operator of the container terminal. When the length of each wire rope 3 that can be wound by the winding device 2 is equal to or greater than the threshold length ΔL, it can be considered that the container Ca can be lifted, i.e., the container Ca has been lifted from the ground.

[0044] In step S130, it is sufficient to determine whether the container Ca has been lifted from the ground, and the conditions to be set can be selected as appropriate. For example, the condition may be simply the detection of the maximum point P3 in the load data D2, or the time elapsed since the lifting of the hoisting device 4 was completed. However, in order to more accurately determine whether the container Ca has been lifted from the ground, it is desirable to set various conditions rather than limiting the condition to one.

[0045] In step S140, the arithmetic device 6 executes data processing to continue limiting the winding speed of the winding device 2 to the speed limit Va. In step S150, the arithmetic device 6 executes data processing to release the limit on the winding speed of the winding device 2.

[0046] Next, a process of lifting a container Ca by the crane 1 implementing the control method illustrated in FIG. 6 will be described.

[0047] FIG. 8 shows the detection status of the twist lock sensor 11 and the landing sensor 12 in each process, the command value [%] for the winding speed of the winding device 2, and the applied winding speed [%]. The command value is a target value for the winding speed of the winding device 2 generated by the operation device or the calculation device 6. The applied winding speed is the actual winding speed of the winding device 2. The processes in the leftmost column are performed in order from top to bottom. The thick arrows in the figure indicate the same action or value as in the upper row (previous process).

[0048] First, steps (1) to (3) are carried out as preparation steps. In step (1), the hoisting device 4 is landed on the container Ca to be handled. At this time, the landing sensor 12 detects that the hoisting device 4 has landed on the container Ca (ON). Next, in step (2), the twist lock 10 connects the hoisting device 4 to the container Ca. At this time, the twist lock sensor 11 detects that the hoisting device 4 has been connected to the container Ca by the twist lock 10 (ON). Next, in step (3), the lashing device LD that connects and fastens the container Ca and container Cb is removed.

[0049] When the preparation process is completed, the processes from step (4) onwards are executed as the lifting process. In step (4), 100% (rated value) is input as the command value for the winding speed. Next, in step (5), the calculation device 6 limits the winding speed of the winding device 2 to the speed limit Va, and the winding device 2 starts winding each wire rope 3 at the speed limit Va. Next, in step (6), the landing sensor 12 detects (OFF) that the lifting of the hoisting device 4 has been completed. Next, in step (7), the calculation device 6 determines that one side of the container Ca has been completed. Next, in step (8), when the calculation device 6 determines that the lifting of the container Ca has been completed, the limitation of the winding speed to the speed limit Va is lifted. Then, the winding device 2 winds each wire rope 3 at a winding speed according to the command value.

[0050] In the lifting process, when the landing sensor 12 detects that the lifting device 4 has been lifted to the ground in step (6), the reeling of each wire rope 3 by the reeling device 2 may be temporarily stopped. Also, since it is not essential to identify the lifting of one side of the container Ca, step (7) can be omitted.

[0051] As described above, according to this embodiment, even if a winding speed equal to or greater than the rated value (e.g., 100[%]) is input as a command value, the winding speed applied to the winding device 2 is limited to the speed limit Va until the container Ca is lifted from the ground. The time required to stop the winding device 2 to which such a limit is imposed is the same as the time it takes to reduce the winding speed from the speed limit Va to zero, so if an overload occurs while the container Ca is not lifted from the ground by the lashing device LD, the winding device 2 can be stopped more quickly. As a result, the load on the winding device 2 and the crane 1 due to the overload that occurs can be reduced.

[0052] As a common measure to deal with overloads, cranes 1 are sometimes equipped with snag load prevention devices designed to loosen the wire ropes 3. These snag load prevention devices utilize shear pins. When the shear pins break due to overload, they move the sheaves around which the wire ropes 3 are wound, loosening them, thereby reducing the load caused by the overload. Restoring the snag load prevention device after it has been activated requires significant effort, resulting in reduced cargo handling efficiency. According to this embodiment, the reeling device 2 can be reliably stopped before the shear pins break when an overload occurs. Furthermore, because the time required to stop the reeling device 2 is short and the reeling device 2 can unwind the wire ropes 3 after stopping, the time the overload acts on the shear pins when an overload occurs can be further reduced. This reduces the deterioration of the shear pins' durability, thereby avoiding unnecessary shear pin breakage. Generally speaking, this embodiment can significantly reduce the frequency with which the snag load prevention device operates, thereby reducing the time required to restore the snag load prevention device and improving cargo handling efficiency.

[0053] Furthermore, the time required to lift the same container under the same conditions is roughly the same for a conventional winding device and a winding device 2 to which the control method of this embodiment is applied and to which the speed limit Va is imposed. Therefore, even if the control method of this embodiment is implemented, cargo handling efficiency will not be significantly reduced.

[0054] Although the embodiments of the present invention have been described above, the motorized crane and control method of the present invention are not limited to the specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0055] 1 crane 2 Winding device 3a(3b), 3c(3d) Wire rope 4 Hanging equipment 5. Load measuring device 6 Arithmetic unit 7 digit part 8 Trolley 9 Flipper 10 Twist Lock 11 Twistlock sensor 12 Implantation sensor 13 Machine room 14a, 14b double rod cylinder 15 Storage section Ca, Cb container UD upper deck LD Securing Device Va speed limit

Claims

1. A crane equipped with a winding device that winds and unwinds a wire rope connected to a sling, a load measuring device that acquires load data that indicates changes over time in load values ​​acting on the wire rope, and a computing device that processes the load data, a memory unit that stores a speed limit set to 30% or less of a rated winding speed of the winding device, When the winding device winds up the wire rope and lifts the load attached to the sling, the computing device performs data processing to determine completion of the load being lifted from the ground based on the load data, and controls to limit the winding speed of the winding device to the limited speed until the load is lifted from the ground, and to release the limit on the winding speed to the limited speed when the load is lifted from the ground.

2. 2. The crane according to claim 1, wherein the data processing determines that lifting of the load from the ground is complete when a maximum point is detected in the load data.

3. The crane according to claim 2, wherein at least 60% of the load values ​​of 5 to 15 consecutive load values ​​detected immediately after the load value of the local maximum point is less than the load value of the local maximum point.

4. The crane according to claim 2, wherein the data processing determines that the load has not been lifted from the ground if the time elapsed from the completion of lifting of the lifting tool to the detection of the maximum point is less than a preset threshold value.

5. The crane according to claim 4, wherein the threshold value is a value within a range of 1.0 seconds to 2.0 seconds.

6. 6. The crane according to claim 4 or 5, wherein, in the data processing, if the maximum point is not detected after a time equal to or greater than the threshold has elapsed, the lifting of the load from the ground is deemed to be completed when the length of the wire rope wound by the winding device becomes equal to or greater than a predetermined threshold length.

7. The crane according to any one of claims 1 to 5, wherein the speed limit is a speed within a range of 10% to 20% of a rated value of the winding speed of the winding device.

8. A method for controlling a crane that winds a wire rope using a winding device and lifts a load using a hoisting tool connected to the wire rope, comprising: When lifting the load, a speed limit is set to 30% or less of the rated value of the winding speed of the winding device, and winding of the wire rope by the winding device is started at this speed limit; load data indicating a change over time in the load value acting on the wire rope is acquired by a load measuring device; A crane control method in which the acquired load data is processed by a computing device to determine whether the cargo has been lifted from the ground, and when the cargo has been lifted from the ground, the cargo is lifted at a preset winding speed.

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