Suspended load derivation method and crane

Abstract

To avoid the adverse effect of a heavy suspended load on various kinds of processing due to the operation of a boom when the boom is raised and lowered by the power of a hydraulic cylinder.SOLUTION: The crane 10 raises and lowers the boom 2 by the hydraulic cylinder 433. The processor 60 derives the pressure loss caused by the flow of the hydraulic fluid accompanying the operation of the hydraulic cylinder 433 based on the variation amount of the variable parameter representing the derricking operation of the boom 2 (S102). Further, the processor 60 derives the suspended load of the boom 2 based on the detected values of the head pressure and the rod pressure of the hydraulic cylinder 433 and the derived pressure loss (S103).SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for deriving a lifting load of a boom and a crane. [Background technology]

[0002] In the crane, the control device derives the lifting load of the boom and causes the derivation result of the lifting load to be displayed on the display device.

[0003] The control device outputs the derived information on the lifting load to a display device. Furthermore, the control device executes various safety controls, such as outputting an alarm, when the derived lifting load exceeds a limit load.

[0004] For example, the hydraulic device of the crane may include a hydraulic cylinder that raises and lowers the boom. In this case, the control device can derive the thrust of the hydraulic cylinder based on the head pressure and rod pressure of the hydraulic cylinder.

[0005] It is known that the control device derives the lifting load based on the derived thrust of the hydraulic cylinder and information on the shape and attitude of the boom (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-186155 Summary of the Invention [Problem to be solved by the invention]

[0007] Incidentally, an increase or decrease in the lifting load is reflected as an increase or decrease in the difference between the head pressure of the hydraulic cylinder and the rod pressure of the hydraulic cylinder corrected by a correction coefficient. The correction coefficient is set based on the cylinder diameter, rod diameter, etc. of the hydraulic cylinder.

[0008] However, when the boom is in the raising or tilting operation, the flow of hydraulic oil accompanying the operation of the hydraulic cylinder causes a pressure loss of the hydraulic oil in the hydraulic device.

[0009] Therefore, when the hoisting load is calculated based on the head pressure and rod pressure of the hydraulic cylinder, an error in the calculation of the hoisting load occurs due to the pressure loss.

[0010] Specifically, when the boom is in an erecting operation, a value greater than the actual load value is derived as the lifting load, and when the boom is in a tilting operation, a value smaller than the actual load value is derived as the lifting load.

[0011] The error in deriving the lifting load may lead to an incorrect judgment by the pilot or an incorrect control by the control device.

[0012] An object of the present invention is to provide a method for deriving a lifting load and a crane that can avoid the adverse effect on various processes of a lifting load with a large error caused by the operation of the boom when the boom is raised and lowered by the power of a hydraulic cylinder. [Means for solving the problem]

[0013] A method for deriving a lifting load according to one aspect of the present invention is a first method for deriving a lifting load of a boom of a crane that raises or lowers a boom using a hydraulic cylinder. The first method includes a processor deriving a pressure loss caused by the flow of hydraulic oil accompanying operation of the hydraulic cylinder based on a change in a variable parameter representing the boom hoisting operation. The first method further includes the processor deriving the lifting load based on detected values ​​of head pressure and rod pressure of the hydraulic cylinder, detected value of the boom angle, and the derived pressure loss.

[0014] A crane according to another aspect of the present invention includes a boom, a hydraulic device, a head pressure detection device, a rod pressure detection device, a boom angle detection device, and the processor that derives the boom's lifting load using the first method. The boom is supported so as to be able to be raised and lowered and is capable of lifting a load. The hydraulic device includes a hydraulic cylinder that raises and lowers the boom. The head pressure detection device detects the head pressure of the hydraulic cylinder. The rod pressure detection device detects the rod pressure of the hydraulic cylinder. The boom angle detection device detects the angle of the boom.

[0015] A second method for deriving a lifting load according to another aspect of the present invention is a method for deriving a lifting load of a boom of a crane that raises or lowers a boom using a hydraulic cylinder. The second method includes a processor deriving the lifting load based on the detected values ​​of head pressure and rod pressure of the hydraulic cylinder and the detected value of the boom angle and updating the lifting load to the derived value when a change in a variable parameter representing the boom hoisting operation represents a stopped state of the boom. The second method further includes the processor maintaining the lifting load without updating it when the change in the variable parameter represents a tilting operation of the boom.

[0016] A crane according to another aspect of the present invention includes the boom, the hydraulic device, the head pressure detection device, the rod pressure detection device, the boom angle detection device, and the processor that derives the lifting load of the boom using the second method. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a method for deriving a lifting load and a crane that can avoid the adverse effect on various processes of a lifting load with a large error caused by the operation of the boom when the boom is raised and lowered by the power of a hydraulic cylinder. [Brief explanation of the drawings]

[0018] [Figure 1]FIG. 1 is a configuration diagram of a crane according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing the configuration of control-related devices in the crane according to the embodiment. [Figure 3] FIG. 3 is a block diagram showing the configuration of the control device in the crane according to the embodiment. [Figure 4] FIG. 4 is a flowchart showing a first example of a procedure for processing to derive a suspended load in the crane according to the embodiment. [Figure 5] FIG. 5 is a flowchart showing an example of a procedure for a hanging load handling process in the crane according to the embodiment. [Figure 6] FIG. 6 is a flowchart illustrating an example of a procedure for parameter adjustment processing in the crane according to the embodiment. [Figure 7] FIG. 7 is a flowchart showing a second example of the procedure of the processing for deriving the suspended load in the crane according to the embodiment. [Figure 8] FIG. 8 is a flowchart showing a third example of the procedure of the processing for deriving the suspended load in the crane according to the embodiment. [Figure 9] FIG. 9 is a graph showing an example of the relationship between the flow rate of hydraulic oil flowing in the elevation cylinder and pressure loss. [Figure 10] FIG. 10 is a schematic cross-sectional view of an undulating cylinder. [Figure 11] FIG. 11 is a flowchart showing a fourth example of the procedure of the processing for deriving the suspended load in the crane according to the embodiment. [Figure 12] FIG. 12 is a graph showing an example of the relationship between the dimensionless characteristic number and the friction coefficient for the packing of an undulating cylinder. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the following embodiment is an example of the present invention, and does not limit the technical scope of the present invention.

[0020] 1, the crane 10 includes a lower traveling body 11, an upper rotating body 12, a cab 13, a boom 2, a hoisting rope 3, a hoisting device 20, a hoisting device 30, and a hook 300. The hoisting rope 3 is a wire rope.

[0021] The upper rotating body 12 is a rotating body that is rotatably supported by the lower traveling body 11. The cab 13, the hoisting device 20, and the hoisting device 30 are supported by the upper rotating body 12.

[0022] The lower traveling body 11 is a base portion that rotatably supports the upper rotating body 12. The upper rotating body 12 is driven by a rotating device (not shown) provided on the lower traveling body 11 to rotate along a horizontal plane.

[0023] 1 is a mobile crane. Therefore, the crane 10 further includes a traveling device 14. The traveling device 14 supports the lower traveling body 11 and is capable of traveling.

[0024] 1 shows an example in which the traveling device 14 is a crawler type device. However, the traveling device 14 may also be a wheel type device having a plurality of tires. The crane 10 further includes outriggers (not shown).

[0025] The cab 13 is a control room. The base of the boom 2 is connected to the upper rotating body 12. The boom 2 can be raised and lowered around the base connected to the upper rotating body 12.

[0026] The hoisting device 20 changes the angle of the boom 2. The angle of the boom 2 is the elevation angle of the boom 2.

[0027] The hoisting rope 3 is hung on an idler sheave 31 and a main sheave 32 provided at the tip of the boom 2. The hook 300 is suspended by the hoisting rope 3. That is, the hoisting rope 3 is connected to the hook 300 and hangs down from the tip of the boom 2.

[0028] The hoisting device 30 changes the length of the hanging portion of the hanging rope 3 by winding up or letting out the hanging rope 3. The hanging portion is the portion of the hanging rope 3 that hangs down from the tip of the boom 2.

[0029] The change in the length of the hanging part causes the hook 300 to rise and fall. A load is suspended from the hook 300. The boom 2 hoists the load via the hoisting rope 3 and the hook 300.

[0030] In this embodiment, the boom 2 is a telescopic boom that can be extended and retracted. Therefore, the boom 2 includes a plurality of box booms 2a that are connected so as to be able to be extended and retracted (see FIG. 1). The crane 10 further includes a boom extension device 21 that extends and retracts the boom 2 (see FIG. 1).

[0031] 2 , the crane 10 further includes an engine 1, a hydraulic device 4, an operating device 5, a control device 6, a display device 7, and a state detection device 8. The hydraulic device 4 includes a hydraulic pump 41, a plurality of hydraulic control valves 42, and a plurality of actuators 43.

[0032] Each of the actuators 43 is a hydraulic actuator. The control device 6 controls the crane 10.

[0033] Devices for human interface, such as the operation device 5 and the display device 7, are provided in the cab 13. The operation device 5 is a device that accepts operations by the operator. The operation device 5 is an example of an operation unit that accepts operations by a person. The display device 7 is a device that displays information.

[0034] For example, the display device 7 is a panel display device such as a liquid crystal display unit, etc. The operation device 5 includes a lever operation device 51, an operation button 52, an input device 53, and the like.

[0035] The lever operating device 51 includes a plurality of displaceable operating levers 511, 512, and 513. The lever operating device 51 further includes a displacement detecting device 510 that outputs an operating signal Sx1 that indicates the displacement state of each of the plurality of operating levers 511, 512, and 513.

[0036] The operation signal Sx1 indicates the direction of displacement of each of the plurality of operation levers 511, 512, and 513 from its home position and the amount of displacement from the home position.

[0037] The plurality of operation levers 511, 512, 513 include a swivel operation lever 511, a hoisting operation lever 512, and a lifting operation lever 513.

[0038] The multiple actuators 43 include a swing motor 431, one or more boom extension cylinders 432, a boom-lifting cylinder 433, and a winch motor 434.

[0039] The swing motor 431 and the winch motor 434 are hydraulic motors, and the boom extension cylinder 432 and the boom derrick cylinder 433 are hydraulic cylinders.

[0040] The swing motor 431 is a part of the swing device, and is a drive source that rotates the upper swing body 12. When the swing motor 431 rotates, the upper swing body 12 rotates.

[0041] The hoisting cylinder 433 is part of the hoisting device 20. The hoisting cylinder 433 is connected to the upper rotating body 12 and the boom 2, and raises or lowers the boom 2 (see Figure 1). The boom 2 is raised when the hoisting cylinder 433 extends. The boom 2 is tilted when the hoisting cylinder 433 retracts.

[0042] The winch motor 434 is a part of the hoisting device 30. The hoisting device 30 includes a winch that winds up or unwinds the hoisting rope 3. The winch motor 434 is a drive source for the winch.

[0043] When the winch motor 434 rotates in the first direction, the hoisting device 30 winds up the hoisting rope 3. When the winch motor 434 rotates in the second direction, the hoisting device 30 pays out the hoisting rope 3.

[0044] The boom telescopic cylinder 432 is a part of the boom telescopic device 21. For example, the boom telescopic device 21 includes one or more boom telescopic cylinders 432, a plurality of fixed sheaves, and interlocking ropes.

[0045] The fixed sheaves are attached to portions of the box booms 2a. The interlocking rope is a wire rope with both ends connected to portions of the box booms 2a. The interlocking rope is hung on the sheaves.

[0046] The boom 2 extends when the boom telescopic cylinder 432 extends, and the boom 2 retracts when the boom telescopic cylinder 432 retracts. The boom telescopic cylinder 432 is an example of a hydraulic actuator that extends and retracts the boom 2.

[0047] The swing operation lever 511 receives an operation to instruct the operation of the swing motor 431. The hoisting operation lever 512 receives an operation to instruct the operation of the hoisting cylinder 433. The lifting operation lever 513 receives an operation to instruct the operation of the winch motor 434.

[0048] The operation of the swing operation lever 511 is an operation to adjust the amount of hydraulic oil supplied to the swing motor 431. The operation of the hoisting operation lever 512 is an operation to adjust the amount of hydraulic oil supplied to the hoisting cylinder 433. The operation of the lifting operation lever 513 is an operation to adjust the amount of hydraulic oil supplied to the winch motor 434.

[0049] The input device 53 accepts information input by the operator. For example, the input device 53 is a touch panel that is integrated with the display device 7. The input device 53 may also be a device that accepts information input by voice operation of the operator.

[0050] The operating device 5 also includes a telescopic operating unit (not shown) that receives operations to instruct the operation of the boom telescopic cylinder 432.

[0051] The engine 1 drives a hydraulic pump 41. For example, the engine 1 is a diesel engine. The hydraulic pump 41 pressurizes hydraulic oil.

[0052] The plurality of hydraulic control valves 42 adjust the amount of hydraulic oil supplied from the hydraulic pump 41 to the plurality of actuators 43 in accordance with a control signal output from the control device 6 .

[0053] The state detection device 8 detects the state of various devices provided on the crane 10. The various detection results of the state detection device 8 are input to the control device 6. The state detection device 8 includes a plurality of oil pressure gauges 81, a boom angle gauge 82, a rotation speed gauge 83, and the like.

[0054] The plurality of hydraulic pressure gauges 81 detect the pressure of the hydraulic oil at various points in the hydraulic device 4. The plurality of hydraulic pressure gauges 81 constitute a part of the hydraulic device 4.

[0055] The boom angle meter 82 is an example of a boom angle detection device that detects the angle of the boom 2. For example, the boom angle meter 82 may be an inclinometer attached to the boom 2. In this case, the boom angle meter 82 detects the angle that the longitudinal direction of the boom 2 makes with respect to the horizontal direction.

[0056] The plurality of hydraulic pressure gauges 81 include a head pressure gauge 81 a and a rod pressure gauge 81 b that detect the pressure of the hydraulic oil in the elevation cylinder 433 .

[0057] The head pressure gauge 81a is an example of a head pressure detection device that detects the head pressure, which is the pressure of the hydraulic oil on the head side of the elevation cylinder 433. The rod pressure gauge 81b is an example of a rod pressure detection device that detects the rod pressure, which is the pressure of the hydraulic oil on the rod side of the elevation cylinder 433.

[0058] The tachometer 83 detects the rotation speed of the engine 1. The rotation speed of the engine 1 is changed by operating the operation device 5. For example, the engine 1 rotates at an arbitrary speed that is set, or at a speed selected from a plurality of predetermined candidate speed levels.

[0059] The control device 6 outputs a control signal to a control target such as the hydraulic control valve 42 in response to an operation on the operating device 5 or detection results from various state detection devices 8. Furthermore, the control device 6 starts the engine 1 when a start operation is performed on the operating device 5. The control device 6 also controls the display device 7.

[0060] 3, the control device 6 includes an MPU (Micro Processing Unit) 60, a RAM (Random Access Memory) 61, a nonvolatile memory 62, and a signal interface 63. The RAM 61 and the nonvolatile memory 62 are computer-readable storage devices.

[0061] The MPU 60 performs various data processing and control operations by executing computer programs stored in advance in the non-volatile memory 62. The MPU 60 is an example of a processor.

[0062] The RAM 61 is a volatile memory that temporarily stores the programs executed by the MPU 60 and data derived or referenced by the MPU 60 .

[0063] The nonvolatile memory 62 stores in advance the computer program executed by the MPU 60 and data referenced by the MPU 60. For example, the nonvolatile memory 62 may be an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory.

[0064] The signal interface 63 converts the detection signal of the state detection device 8 into digital data and transmits it to the MPU 60. Furthermore, the signal interface 63 converts the control command output by the MPU 60 into a control signal such as a current signal or a voltage signal, and outputs it to the device to be controlled.

[0065] The MPU 60 executes the computer program to operate as a plurality of processing modules, which include a determination unit 6a and a control unit 6b (see FIG. 3).

[0066] The determination unit 6a derives various index values ​​used for controlling the crane 10 based on the detection results of the state detection device 8. Furthermore, the determination unit 6a determines various states of the crane 10 based on some of the detection results of the state detection device 8, the index values, and the details of the operation of the operating device 5.

[0067] For example, the determination unit 6a derives the lifting load of the boom 2 based on the detection result of the state detection device 8. Furthermore, the determination unit 6a selects the operation mode of the control device 6 based on the content of the operation on the operation device 5.

[0068] In this embodiment, the determination unit 6a executes a boom length derivation process to derive the boom length. The boom length is the length of the boom 2. The determination unit 6a derives the boom length according to the operation of the boom telescopic cylinder 432 each time the boom telescopic cylinder 432 operates.

[0069] The control unit 6b controls various devices in the crane 10 based on one or both of the detection result of the state detection device 8 and the derived index value. For example, the control unit 6b outputs a control signal corresponding to the operation signal Sx1 to the plurality of hydraulic control valves 42.

[0070] Incidentally, an increase or decrease in the lifting load is reflected as an increase or decrease in the difference between the head pressure of the elevation cylinder 433 and the rod pressure of the elevation cylinder 433 corrected by a pressure correction coefficient. The pressure correction coefficient is set based on the cylinder diameter and rod diameter of the elevation cylinder 433, etc.

[0071] However, when the boom 2 is in the process of raising or tilting, the flow of the hydraulic oil caused by the operation of the boom raising / lowering cylinder 433 causes a pressure loss of the hydraulic oil in the hydraulic device 4.

[0072] Therefore, when the hoisting load is calculated based on the head pressure and the rod pressure of the elevation cylinder 433, an error in the calculation of the hoisting load occurs due to the pressure loss.

[0073] Specifically, when the boom 2 is in the raising operation, a value larger than the actual load value is derived as the lifting load, and when the boom 2 is in the tilting operation, a value smaller than the actual load value is derived as the lifting load.

[0074] The error in deriving the lifting load may lead to an erroneous judgment by the pilot or an erroneous control by the control unit 6b.

[0075] In the crane 10, the determination unit 6a derives the lifting load so that an erroneous lifting load is not derived due to the movement of the boom 2 when the boom 2 is raised or lowered by the power of the raising / lowering cylinder 433.

[0076] [First example of lifting load calculation process] Hereinafter, a first example of the procedure of the hanging load derivation process executed by the determining unit 6a will be described with reference to the flowchart shown in FIG.

[0077] The first example of the lifting load derivation process is a first example of a process that realizes a lifting load derivation method for deriving the lifting load of the boom 2.

[0078] In this embodiment, the determination unit 6a can select one of the normal mode and the adjustment mode as the operation mode in response to a mode selection operation on the operation button 52 or the input device 53.

[0079] When the normal mode is selected, the determination unit 6a repeats the hanging load derivation process at a predetermined cycle. The adjustment mode is the operation mode corresponding to the parameter adjustment process. The parameter adjustment process is a process for deriving correction parameters used to derive the hanging load. The parameter adjustment process will be described later.

[0080] In the following description, S101, S102, ... represent identification symbols of a plurality of steps in the first example of the hanging load derivation process. In the hanging load derivation process, the determination unit 6a first executes the process of step S101.

[0081] <Process S101> In step S101, the determination unit 6a acquires the detected angle, which is the value detected by the boom angle meter 82, and derives the amount of change in angle. The amount of change in angle is the amount of change in the detected angle. The detected angle is an example of a variable parameter that represents the raising and lowering operation of the boom 2.

[0082] For example, the determination unit 6a derives the difference between the detected angle obtained this time and the detected angle obtained one cycle before as the amount of change in angle.

[0083] Alternatively, the determination unit 6a may derive a plurality of unit angle differences over a plurality of periods and derive the average value of the plurality of unit angle differences as the amount of change in angle. Each unit angle difference is the difference between the detected angle at the current time and the detected angle at the previous time for each period.

[0084] The determination unit 6a shifts the process from step S101 to step S102.

[0085] <Process S102> In step S102, the determination unit 6a derives the pressure loss based on the angle change amount derived in step S101.

[0086] The pressure loss is an energy loss that occurs in the flow path of the hydraulic oil due to the flow of the hydraulic oil accompanying the operation of the boom raising / lowering cylinder 433. When the amount of change in angle represents a stopped state of the boom 2, the determination unit 6a sets the pressure loss to zero.

[0087] Specifically, the determination unit 6a derives the head-side pressure loss and the rod-side pressure loss as the pressure losses. The head-side pressure loss is the energy loss in the circuit on the head side of the undulating cylinder 433 in the specific circuit. The rod-side pressure loss is the energy loss in the circuit on the rod side of the undulating cylinder 433 in the specific circuit.

[0088] For example, the determining unit 6a derives the head side pressure loss and the rod side pressure loss through the processing of steps S102a to S102c.

[0089] In step S102a, the determining unit 6a derives the cylinder speed of the elevation cylinder 433 by applying the angle change amount to a preset speed calculation formula or speed conversion table.

[0090] The speed calculation formula or the speed conversion table is set based on the various dimensions and positional relationships of the boom 2 and the hoisting cylinder 433.

[0091] In step S102b, the determination unit 6a derives a specific oil volume by applying the cylinder speed to a preset flow rate calculation formula or a flow rate conversion table. The specific oil volume is the flow rate of the hydraulic oil flowing through a specific circuit including the elevation cylinder 433 in the hydraulic circuit of the hydraulic device 4.

[0092] The flow rate calculation formula or the flow rate conversion table is set based on the cylinder diameter and rod diameter of the undulating cylinder 433, etc.

[0093] In step S102c, the determination unit 6a derives the head-side pressure loss by applying the specific oil quantity to a preset first loss calculation formula or a preset first loss conversion table. Furthermore, the determination unit 6a derives the rod-side pressure loss by applying the specific oil quantity to a preset second loss calculation formula or a preset second loss conversion table.

[0094] The first loss calculation formula or the first loss conversion table is set based on the pipe friction coefficient, the pipe length, the pipe inner diameter, etc. for the head side portion of the undulating cylinder 433 in the specific circuit.

[0095] Similarly, the second loss calculation formula or the second loss conversion table is set based on the pipe friction coefficient, pipe length, pipe inner diameter, etc. for the rod side portion of the undulating cylinder 433 in the specific circuit.

[0096] Figure 9 shows an example of the correspondence relationship between the specific oil quantity and the head-side pressure loss. The specific oil quantity and the head-side pressure loss have a nonlinear positive correlation. The first loss calculation formula or the first loss conversion table exhibits, for example, the characteristics shown in Figure 9. The correspondence relationship between the specific oil quantity and the rod-side pressure loss is also similar.

[0097] The determination unit 6a may derive the head-side pressure loss and the rod-side pressure loss by applying the angle change amount to a preset direct conversion table, which represents a correspondence relationship between the angle change amount and the head-side pressure loss and the rod-side pressure loss.

[0098] The determination unit 6a shifts the process from step S102 to step S103.

[0099] <Process S103> In step S103, the determination unit 6a acquires the head pressure detection value and the rod pressure detection value corresponding to the elevation cylinder 433, and derives the suspension load. The head pressure detection value and the rod pressure detection value are detection values ​​of the head pressure gauge 81a and the rod pressure gauge 81b, respectively.

[0100] In step S103, the determination unit 6a derives the suspension load based on the head pressure detection value, the rod pressure detection value, and the pressure loss derived in step S102.

[0101] For example, the determination unit 6a derives the suspension load through the processes of steps S103a to S103d.

[0102] In step S103a, the determination unit 6a derives the sum of the head pressure detection value and the head-side pressure loss as the head-side pressure. Furthermore, the determination unit 6a derives the pressure obtained by correcting the sum of the rod pressure detection value and the rod-side pressure loss by the pressure correction coefficient as the rod-side corrected pressure.

[0103] In step S103b, the determination unit 6a derives the difference between the head-side pressure and the rod-side corrected pressure as the support pressure.

[0104] In step S103c, the determination unit 6a derives the boom weight pressure based on multiple boom-related parameters. The boom weight pressure is the difference between the hydraulic pressure on the head side and the hydraulic pressure on the rod side of the boom deriving cylinder 433, which is generated by the weight of the boom 2 and the members attached to the boom 2.

[0105] The plurality of boom-related parameters include the boom length, the boom-related mass, and the detected angle. The boom-related mass is the mass of the boom 2 and a member attached to the boom 2.

[0106] In step S103d, the determination unit 6a derives the load differential pressure, which is the difference between the support pressure and the boom weight pressure, as the hoisting load. Note that the determination unit 6a may derive the hoisting load by applying the load differential pressure, the boom length, the detected angle, etc. to a preset load conversion formula.

[0107] In the example described above, the determination unit 6a derives the lifting load based on the detected values ​​of the head pressure, the rod pressure, and the boom angle, and the derived boom length and pressure loss. The determination unit 6a shifts the process from step S103 to step S104.

[0108] <Process S104> In step S104, the determination unit 6a updates the suspension load used for display on the display device 7 and for various controls to the suspension load derived in step S103.

[0109] When the first example of the hanging load derivation process is adopted, the latest hanging load updated in step S104 is used for subsequent display on the display device 7 and various controls.

[0110] After executing the process of step S104, the determination unit 6a ends the hanging load derivation process. As described above, the determination unit 6a periodically repeats the processes of steps S101 to S104.

[0111] The determination unit 6a executes the lifting load derivation process to derive the lifting load from which the pressure loss factor has been removed, thereby preventing an erroneous lifting load from being derived due to the raising and lowering operation of the boom 2.

[0112] [Hanging load handling] Next, the hanging load response process executed by the control unit 6b will be described with reference to the flowchart shown in Fig. 5. The hanging load response process is a process executed based on the hanging load obtained in step S104.

[0113] When the normal mode is selected, the control unit 6b repeats the hanging load response process at a predetermined cycle. The control unit 6b may also execute the hanging load response process every time the hanging load is updated in step S104.

[0114] In the following description, S201, S202, ... represent identification codes of a plurality of steps in the hanging load handling process. In the hanging load handling process, the control unit 6b first executes the process of step S201.

[0115] <Process S201> In step S201, the control unit 6b derives a limit load based on the plurality of boom-related parameters including the detected value. The limit load is an upper limit of the allowable value of the lifting load to avoid dangerous situations such as the crane 10 tipping over.

[0116] The control unit 6b shifts the process from step S201 to step S202.

[0117] <Process S202> In step S202, the control unit 6b determines whether the current value of the suspension load exceeds the limit load.

[0118] The control unit 6b shifts the process to step S203 if the current value of the suspending load does not exceed the limit load, whereas the control unit 6b shifts the process to step S204 if the current value of the suspending load exceeds the limit load.

[0119] <Process S203> In step S203, the control unit 6b executes normal output of the hoisting load, which is a process of causing the display device 7 to display the hoisting load in a normal display format.

[0120] After executing the process of step S203, the control unit 6b ends the hanging load handling process.

[0121] <Process S204> In step S204, the control unit 6b executes an overload prevention process.

[0122] The overload prevention process includes outputting an alarm, which includes either or both of a process of outputting an alarm sound through a speaker (not shown) and a process of displaying the suspended load in an alarm format on the display device 7.

[0123] The overload prevention process may also include a process for prohibiting predetermined target operations by some or all of the multiple actuators 43. For example, the target operations include the operation of the hoisting cylinder 433 that tilts the boom 2, the operation of the winch motor 434 that pays out the hoisting rope 3, or the operation of the boom telescopic cylinder 432 that extends the boom 2.

[0124] When a predetermined restriction release operation is performed on the operation device 5, the control unit 6b releases the prohibition on the target action.

[0125] After executing the process of step S204, the control unit 6b ends the hanging load handling process.

[0126] By executing the hoisting load response process, it is possible to prevent the crane 10 from being put into a dangerous state due to an excessive hoisting load.

[0127] Furthermore, when the hanging load is derived by the first example of the hanging load derivation process, it is possible to prevent the hanging load with a large error resulting from the operation of the boom 2 from adversely affecting various processes. Specifically, it is possible to prevent the hanging load derivation error resulting from the pressure loss from leading to omission of the overload prevention process.

[0128] [Parameter adjustment process] Next, an example of the procedure of the parameter adjustment process executed by the determination unit 6a will be described with reference to the flowchart shown in Fig. 6. The determination unit 6a executes the parameter adjustment process when the adjustment mode is selected.

[0129] In the following description, S301, S302, ... represent identification codes of a plurality of steps in the parameter adjustment process. In the parameter adjustment process, the determination unit 6a first executes the process of step S301.

[0130] <Process S301> In step S301, the determination unit 6a executes a process of notifying a first guidance through the display device 7. The first guidance includes information instructing that a calibration weight be hung from the hook 300 and that the boom 2 hanging the calibration weight be kept stopped. The calibration weight is a weight with a known mass.

[0131] The determination unit 6a shifts the process from step S301 to step S302.

[0132] <Process S302> In step S302, the determining unit 6a waits until a predetermined confirmation operation is performed on the operation device 5.

[0133] When the crane 10 is in a state following the instructions of the first guidance, the operator performs the confirmation operation on the operation device 5. When the confirmation operation is performed on the operation device 5, the determination unit 6a shifts the processing from step S302 to step S303.

[0134] <Process S303> In step S303, the determining unit 6a derives the amount of change in angle, similarly to step S101 in FIG.

[0135] In the following description, the angle change amount derived in step S303 will be referred to as the first angle change amount. The first angle change amount is the angle change amount after the first guidance is notified. The first angle change amount is an example of a first parameter change amount. The determination unit 6a shifts the process from step S303 to step S304.

[0136] <Process S304> In step S304, the determination unit 6a repeats the process of step S303 until the first angle change amount indicates that the boom 2 is in a stopped state.

[0137] For example, the determination unit 6a determines that the first angle change amount represents the stopped state of the boom 2 when the first angle change amount is within a reference range including zero.

[0138] When the determining unit 6a determines that the first angle change amount indicates that the boom 2 is in a stopped state, the determining unit 6a shifts the processing from step S304 to step S305.

[0139] <Process S305> In step S305, the determination unit 6a sets the pressure loss to 0 and executes the processes of steps S103 and S104 in FIG. 1 to derive the first hanging load.

[0140] That is, the determination unit 6a derives the first lifting load based on the head pressure detection value and the rod pressure detection value, with the pressure loss set to 0. The first lifting load is the lifting load when the first angle change amount indicates that the boom 2 is in a stopped state.

[0141] The determination unit 6a shifts the process from step S305 to step S306.

[0142] <Process S306> In step S306, the determination unit 6a derives a first correction parameter, which is a part of the correction parameters, by comparing a preset calibration load with the first suspension load.

[0143] The calibration load is the mass of the calibration weight corresponding to the first guide, and the first correction parameter is a parameter related to correction of the hanging load when the pressure loss is zero.

[0144] The determining unit 6a derives, as the first correction parameter, a correction coefficient for making the derivation result of the hanging load when the pressure loss is 0 coincide with the calibrated load.

[0145] The determination unit 6a shifts the process from step S306 to step S307.

[0146] <Process S307> In step S307, the determination unit 6a executes a process of notifying a second guidance through the display device 7. The second guidance includes information instructing an operation to tilt the boom 2 that suspends the calibration weight.

[0147] The determination unit 6a shifts the process from step S307 to step S308.

[0148] <Process S308> In step S308, the determination unit 6a derives the amount of change in angle, similarly to step S101 in FIG.

[0149] In the following description, the angle change amount derived in step S308 will be referred to as the second angle change amount. The second angle change amount is the angle change amount after the second guidance is notified. The second angle change amount is an example of a second parameter change amount. The determination unit 6a shifts the process from step S308 to step S309.

[0150] <Process S309> In step S309, the determination unit 6a determines whether or not the second angle change amount represents a tilting operation of the boom 2. The determination unit 6a repeats the processing of step S308 until the second angle change amount represents a tilting operation of the boom 2.

[0151] For example, the determining unit 6a determines that the first angle change amount represents a tilting operation of the boom 2 when the second angle change amount is smaller than the reference range.

[0152] When the determining unit 6a determines that the second angle change amount represents a tilting operation of the boom 2, the determining unit 6a shifts the processing from step S309 to step S310.

[0153] <Process S310> In step S310, the determination unit 6a derives the second hanging load by executing the processes of steps S102 to S104 in FIG.

[0154] The second lifting load is the lifting load when the first angle change amount represents the tilting operation of the boom 2. The second lifting load is derived using the pressure loss and the first correction parameter derived in step S306.

[0155] The determination unit 6a shifts the process from step S310 to step S311.

[0156] <Process S311> In step S311, the determining unit 6a derives a second correction parameter, which is a part of the correction parameters, by comparing the calibration load with the second hanging load. The second correction parameter is a parameter related to the pressure loss.

[0157] Specifically, the second correction parameter is a correction coefficient for correcting the pressure loss. The determination unit 6a derives, as the second correction parameter, a correction coefficient for making the result of deriving the suspension load based on the head pressure detection value, the rod pressure detection value, and the pressure loss coincide with the calibrated load.

[0158] After executing the process of step S311, the determination unit 6a ends the parameter adjustment process. The determination unit 6a records the derived correction parameters in the nonvolatile memory 62.

[0159] Furthermore, when the normal mode is selected, the determining unit 6a derives the hanging load using the first correction parameter and the second correction parameter in step S103 of FIG.

[0160] The selection of the normal mode is an example of the selection of the adjustment mode. By performing the parameter adjustment process, the derivation error of the hanging load is reduced.

[0161] [Second example of lifting load calculation process] Next, a second example of the procedure of the hanging load derivation process executed by the determining unit 6a will be described with reference to the flowchart shown in FIG.

[0162] The second example of the lifting load derivation process is a second example of a process that realizes a lifting load derivation method for deriving the lifting load of the boom 2.

[0163] When the normal mode is selected, the determination unit 6a may derive the hanging load by executing a second example of the hanging load derivation process.

[0164] In the following description, S401, S402, ... represent identification symbols of a plurality of steps in the second example of the hanging load derivation processing. In the second example of the hanging load derivation processing, the determination unit 6a first executes the processing of step S401.

[0165] <Process S401> In step S401, the determination unit 6a derives the amount of change in angle, similarly to step S101 in FIG.

[0166] The determination unit 6a shifts the process from step S401 to step S402.

[0167] <Process S402> In step S402, the determination unit 6a determines whether or not the second angle change amount represents a tilting operation of the boom 2, similarly to step S309 in FIG.

[0168] The determination unit 6a shifts the process from step S402 to step S403 when it determines that the second angle change amount does not represent a tilting operation of the boom 2. That is, the determination unit 6a shifts the process from step S402 to step S403 when it determines that the second angle change amount represents a stopped state of the boom 2 or an erecting operation of the boom 2.

[0169] On the other hand, when the determining unit 6a determines that the second angle change amount represents a tilting operation of the boom 2, the determining unit 6a shifts the processing from step S402 to step S404.

[0170] <Process S403> In step S403, the determination unit 6a sets the pressure loss to 0. Thereafter, the determination unit 6a shifts the process from step S403 to step S405.

[0171] <Process S404> In step S404, the determination unit 6a derives the pressure loss in the same manner as in step S102 of Fig. 4. Thereafter, the determination unit 6a shifts the process from step S404 to step S405.

[0172] <Process S405> In step S405, the determination unit 6a derives the hanging load in the same manner as in step S103 of Fig. 4. In deriving the hanging load in step S405, the pressure loss obtained by the processing in step S403 or step S404 is used.

[0173] That is, when the derived angle change amount represents a tilting operation of the boom 2, the judgment unit 6a derives the lifting load based on the detected values ​​of the head pressure and the rod pressure and the derived pressure loss (see steps S402, S404, S405).

[0174] On the other hand, when the derived angle change amount indicates that the boom 2 is in an erecting operation or stopped state, the judgment unit 6a sets the pressure loss to 0 and derives the lifting load based on the detected values ​​of the head pressure and the rod pressure (see steps S402, S403, S405).

[0175] The determination unit 6a shifts the process from step S405 to step S406.

[0176] <Process S406> In step S406, the determination unit 6a updates the suspension load used for display on the display device 7 and for various controls to the suspension load derived in step S405.

[0177] When the second example of the hanging load derivation process is adopted, the latest hanging load updated in step S406 is used for subsequent display on the display device 7 and various controls.

[0178] After executing the process of step S406, the determination unit 6a ends the hanging load derivation process. As described above, the determination unit 6a periodically repeats the processes of steps S401 to S406.

[0179] When the second example of the processing for deriving the lifting load is adopted, the lifting load reflecting the pressure loss is used for various processing when the boom 2 is tilting (see steps S404, S405 and S406).

[0180] The first state in which the boom 2 is tilting is a state in which the lifting load, which does not reflect the pressure loss, is likely to be derived as a value smaller than the actual load. In the first state, the lifting load, which reflects the pressure loss, is derived.

[0181] As a result, it is possible to prevent an error in deriving the hanging load due to the pressure loss from leading to an oversight in the execution of the overload prevention process.

[0182] On the other hand, in the second state in which the boom 2 is being raised, the lifting load that does not reflect the pressure loss is likely to be derived as a value larger than the actual load. In the second state, the lifting load that does not reflect the pressure loss is derived.

[0183] In the second state, the error in deriving the hanging load due to the pressure loss does not lead to failure to execute the overload prevention process.

[0184] Therefore, when the hanging load is derived by the second example of the hanging load derivation process, it is possible to prevent the hanging load with a large error resulting from the operation of the boom 2 from adversely affecting various processes. Specifically, it is possible to prevent the hanging load derivation error resulting from the pressure loss from leading to omission of the overload prevention process.

[0185] [Third example of lifting load calculation process] Next, a third example of the procedure of the hanging load derivation process executed by the determining unit 6a will be described with reference to the flowchart shown in FIG.

[0186] The third example of the lifting load derivation process is a third example of a process that realizes a lifting load derivation method for deriving the lifting load of the boom 2.

[0187] When the normal mode is selected, the determination unit 6a may derive the hanging load by executing a third example of the hanging load derivation process.

[0188] In the following description, S501, S502, ... represent identification symbols of a plurality of steps in the third example of the hanging load derivation processing. In the third example of the hanging load derivation processing, the determination unit 6a first executes the processing of step S501.

[0189] <Process S501> In step S501, the determination unit 6a derives the amount of change in angle, similarly to step S101 in FIG.

[0190] The determination unit 6a shifts the process from step S501 to step S502.

[0191] <Process S502> In step S502, the determination unit 6a determines whether or not the second angle change amount represents a tilting operation of the boom 2, similarly to step S309 in FIG.

[0192] As described above, the state in which the second angle change amount does not represent the tilting operation of the boom 2 is the state in which the second angle change amount represents the stopped state or the erecting operation of the boom 2.

[0193] When the determination unit 6a determines that the second angle change amount does not represent a tilting operation of the boom 2, it terminates the lifting load derivation process without deriving or updating the lifting load. This maintains the lifting load that was most recently derived under a situation in which the second angle change amount represents a stopped state or an upright state of the boom 2.

[0194] On the other hand, when the determining unit 6a determines that the second angle change amount represents a tilting operation of the boom 2, the determining unit 6a shifts the processing from step S502 to step S503.

[0195] <Process S503> In step S503, the determination unit 6a derives the suspension load without reflecting the pressure loss, that is, the determination unit 6a derives the suspension load based on the head pressure detection value and the rod pressure detection value.

[0196] The determination unit 6a shifts the process from step S503 to step S504.

[0197] <Process S504> In step S504, the determination unit 6a updates the suspension load used for display on the display device 7 and for various controls to the suspension load derived in step S503.

[0198] As described above, when the derived angle change amount indicates that the boom 2 is stopped or in an erecting motion, the judgment unit 6a derives the lifting load based on the head pressure detection value and the rod pressure detection value and updates the lifting load to the derived value (see steps S502 to S504).

[0199] On the other hand, when the derived angle change amount represents a tilting operation of the boom 2, the determination unit 6a maintains the lifting load without updating it (see Yes in step S502).

[0200] When the third example of the hanging load derivation process is adopted, the same effects as when the second example of the hanging load derivation process is adopted can be obtained.

[0201] [Fourth example of lifting load calculation process] Next, a fourth example of the procedure of the hanging load derivation process executed by the determining unit 6a will be described with reference to FIGS.

[0202] 10, the undulating cylinder 433 includes a cylinder tube 4331, a rod 4332, and a piston 4333. The undulating cylinder 433 further includes a rod packing 433a supported by the cylinder tube 4331 and a piston packing 433b supported by the piston 4333.

[0203] The rod packing 433a slides on the surface of the rod 4332 when the elevation cylinder 433 operates. The piston packing 433b slides on the inner surface of the cylinder tube 4331 when the elevation cylinder 433 operates.

[0204] When the elevation cylinder 433 operates, the packing friction force, which is a dynamic friction force acting on the rod packing 433a and the piston packing 433b, affects the hanging load.

[0205] The friction coefficient of each of rod packing 433a and piston packing 433b changes depending on the acting pressure acting on each packing and the cylinder speed.

[0206] Therefore, the packing friction force changes depending on the operating conditions of the elevation cylinder 433, and becomes a disturbance in the derivation of the lifting load.

[0207] In this modification, the determination unit 6a derives the suspension load in which the influence of the packing friction force is reflected.

[0208] Hereinafter, a fourth example of the procedure of the hanging load derivation process executed by the determining unit 6a will be described with reference to the flowchart shown in FIG.

[0209] The fourth example of the lifting load derivation process is a fourth example of a process that realizes a lifting load derivation method for deriving the lifting load of the boom 2.

[0210] When the normal mode is selected, the determination unit 6a may derive the hanging load by executing a fourth example of the hanging load derivation process.

[0211] The procedure of the hanging load derivation process shown in FIG. 11 is a procedure in which steps S103a to S103d in step S103 of the hanging load derivation process shown in FIG. 4 are replaced with steps S103e to S103i.

[0212] That is, in the fourth example, the determining unit 6a derives the suspension load by executing the processes of steps S103e to S103i instead of the processes of steps S103a to S103d shown in FIG.

[0213] The processing of steps S103e to S103i in step S103 of the fourth example will be described below.

[0214] <Process S103> In step S103, the determination unit 6a acquires the head pressure detection value and the rod pressure detection value corresponding to the elevation cylinder 433, and derives the suspension load by the processing of steps S103e to S103i.

[0215] In step S103e, the determination unit 6a derives the head-side pressure and the rod-side corrected pressure, similarly to step S103a in FIG.

[0216] Furthermore, in step S103f, the determination unit 6a derives the packing friction force based on the head pressure detection value and the rod pressure detection value corresponding to the elevation cylinder 433 and the cylinder speed of the elevation cylinder 433 derived in step S102.

[0217] As described above, the determination unit 6a derives the cylinder speed by applying the angle change amount to a preset speed calculation formula or speed conversion table (see step S102a in FIG. 4). That is, the determination unit 6a derives the packing friction force based on the angle change amount, the head pressure detection value and the rod pressure detection value corresponding to the elevation cylinder 433.

[0218] The packing friction force is the sum of a first kinetic friction force applied to the rod packing 433a and a second kinetic friction force applied to the piston packing 433b.

[0219] Each of the first kinetic friction force and the second kinetic friction force is obtained by multiplying the tension force acting on each packing by the friction coefficient of each packing.

[0220] The tension force is obtained by multiplying the working pressure acting on each packing by the tension force coefficient corresponding to each packing. The working pressure of rod packing 433a is the higher of the rod-side corrected pressure and the head-side pressure derived in step S103e. The working pressure of piston packing 433b is the head-side pressure obtained in step S103e.

[0221] As described above, the determination unit 6a derives the head-side pressure and the rod-side corrected pressure based on the angle change amount and the head pressure detection value and the rod pressure detection value corresponding to the elevation cylinder 433 (see step S103a).

[0222] The tension coefficient is a constant determined by the tension force acting on each packing under atmospheric pressure and the width and circumferential length of the surface of each packing that comes into contact with the cylinder.

[0223] The coefficient of friction has a correlation with the dimensionless characteristic number corresponding to each packing, as shown in Figure 12. Figure 12 shows the relationship between the dimensionless characteristic number and the coefficient of friction for each packing in the liquid lubrication region. In the liquid lubrication region, each packing comes into contact with the rod 4332 or the cylinder tube 4331 via an oil film.

[0224] The dimensionless characteristic number is proportional to the cylinder speed and inversely proportional to the tension force. A characteristic coefficient, which is a proportionality coefficient between the dimensionless characteristic number and the cylinder speed, is a constant determined by the viscosity of the hydraulic oil and the circumferential length of the shaft.

[0225] Therefore, the determination unit 6a derives the tension force of each packing by multiplying each of the rod side corrected pressure and the head side pressure obtained in step S103e by the tension force coefficient.

[0226] Furthermore, the determining unit 6a derives the dimensionless characteristic number by dividing the value obtained by multiplying the cylinder speed by the characteristic coefficient by the tension force.

[0227] Furthermore, the determining unit 6a derives the friction coefficient of each packing by applying the dimensionless characteristic number to the calculation formula or conversion table showing the characteristics shown in FIG.

[0228] Furthermore, the determining unit 6a derives the sum of the kinetic friction forces of each packing obtained by multiplying the tension force of each packing by the friction coefficient of each packing as the packing friction force.

[0229] As described above, the determining unit 6a derives the packing friction force based on the amount of change in angle, the detected head pressure value and the detected rod pressure value corresponding to the elevation cylinder 433, and the pressure loss.

[0230] Furthermore, in step S103g, the determination unit 6a derives the support pressure by adding the packing friction force to the difference between the head side pressure and the rod side corrected pressure.

[0231] That is, the support pressure derived in step S103g is the support pressure derived in step S103b of FIG. 4 corrected by the packing friction force.

[0232] In step S103h, the determination unit 6a derives the boom own weight pressure based on the plurality of boom-related parameters, similar to step S103c.

[0233] In step S103i, similar to step S103d, the determination unit 6a derives the load differential pressure, which is the difference between the support pressure and the boom's own weight pressure, as the hoisting load. Note that the determination unit 6a may derive the hoisting load by applying the load differential pressure, the boom length, the detection angle, etc. to a preset load conversion formula.

[0234] As described above, in the fourth example, the determination unit 6a derives the suspension load corrected by the packing friction force. The determination unit 6a shifts the process from step S103 to step S104.

[0235] When the fourth example of the hanging load derivation process is adopted, the hanging load can be derived with higher accuracy than when the first example of the hanging load derivation process is adopted.

[0236] The process of deriving the suspension load in the fourth example may be applied to the second or third example.

[0237] [5th ​​example of lifting load calculation processing] Next, a fifth example of the procedure of the hanging load derivation process executed by the determining unit 6a will be described.

[0238] In the following description, the direction and amount of displacement of the hoisting operation lever 512 detected by the displacement detection device 510 will be referred to as the hoisting operation amount. The hoisting operation amount is an example of a variable parameter that represents the hoisting operation of the boom 2.

[0239] In the first to fourth examples, the determination unit 6a derives the pressure loss caused by the flow of the hydraulic oil accompanying the operation of the boom raising / lowering cylinder 433 based on the amount of change in angle of the boom 2 (see step 102 in FIG. 4).

[0240] On the other hand, the determination unit 6a of the fifth example derives the amount of change in the amount of undulation operation in step S101.

[0241] For example, the determining unit 6a derives the difference between the amount of undulation operation obtained this time and the amount of undulation operation obtained one cycle before as the amount of change in the amount of undulation operation.

[0242] Furthermore, in step S102, the determining unit 6a derives the pressure loss based on the amount of change in the amount of elevation / depression operation.

[0243] In the fifth example, the nonvolatile memory 62 stores a plurality of speed conversion tables each corresponding to a plurality of candidate rotation speeds that are candidates for the rotation speed of the engine 1.

[0244] Each of the plurality of speed conversion tables is a lookup table that converts the amount of hoisting operation into the cylinder speed of the hoisting cylinder 433.

[0245] In step S102a, the determination unit 6a of the fifth example selects a target conversion table corresponding to the speed detected by the tachometer 83 from the plurality of speed conversion tables.

[0246] Furthermore, the determination unit 6a derives the cylinder speed of the hoisting cylinder 433 by applying the amount of hoisting operation to the object conversion table.

[0247] Furthermore, the determination unit 6a executes the processes of steps S102b to S102c shown in Fig. 4 to derive the head-side pressure loss and the rod-side pressure loss of the elevation cylinder 433. Note that a plurality of speed conversion formulas may be employed instead of the plurality of speed conversion tables.

[0248] When the fifth example is adopted, the same effect as when the first example is adopted can be obtained. [Explanation of symbols]

[0249] 1: Engine 2: Boom 3: Hanging rope 4: Hydraulic system 5: Operating device 6: Control device 7:Display device 8: Status detection device 10: Crane 20:Luffing device 21: Boom extension device 30:Hoisting device 31: Idler sheave 32: Main sheave 41: Hydraulic pump 42: Hydraulic control valve 43: Actuator 51: Lever operating device 52: Operation button 53: Input device 60: MPU (processor) 81: Oil pressure gauge 510: Displacement detection device 511: Turning control lever 512: Elevation control lever 513: Lifting operation lever

Claims

1. A method for deriving a lifting load of a boom in a crane that raises and lowers a boom by a hydraulic cylinder, comprising: a processor deriving a pressure loss caused by a flow of hydraulic oil accompanying operation of the hydraulic cylinder based on a change amount of a variable parameter representing the boom hoisting operation; The processor derives the lifting load based on the detected values ​​of the head pressure and rod pressure of the hydraulic cylinder, the detected value of the boom angle, and the derived pressure loss.

2. The method for deriving a lifting load according to claim 1 , wherein the variable parameter is a detected value of the angle of the boom.

3. 2. The method for deriving a lifting load according to claim 1, wherein the variable parameter is an operation amount of a hoisting operation lever that is operated to adjust the amount of hydraulic oil supplied to the hydraulic cylinder.

4. The processor derives a kinetic friction force acting on a rod packing and a piston packing provided in the hydraulic cylinder based on the change amount of the variable parameter, the detected values ​​of the head pressure and the rod pressure of the hydraulic cylinder, and the pressure loss; The method for deriving a suspension load according to claim 1 , further comprising: the processor deriving the suspension load corrected by the kinetic friction force.

5. When the boom is extendable and retractable and a hydraulic actuator extends and retracts the boom, the processor further deriving a length of the boom in response to operation of the hydraulic actuator; The method for deriving a lifting load according to any one of claims 1 to 3, wherein the processor derives the lifting load based on the detected values ​​of the head pressure, the rod pressure, and the boom angle, and the derived length of the boom and the pressure loss.

6. the processor derives the lifting load based on the detected values ​​of the head pressure and the rod pressure and the derived pressure loss when the amount of change in the variable parameter represents a tilting operation of the boom; 4. The method for deriving a lifting load according to claim 1, wherein the processor, when the amount of change in the variable parameter represents the raising operation of the boom or the stopped state of the boom, derives the lifting load based on the detected values ​​of the head pressure and the rod pressure, with the pressure loss set to 0.

7. The method further includes executing a parameter adjustment process by the processor to derive a correction parameter used in deriving the suspension load when an adjustment mode is selected; The parameter adjustment process includes: the processor notifying a first instruction instructing the boom suspending the calibration weight to be kept stationary; the processor deriving a first parameter change amount, which is a change amount of the variable parameter after the first guidance is notified; the processor deriving a first lifting load, which is the lifting load when the first parameter change amount represents a stopped state of the boom; the processor notifies a second guide instructing an operation to raise or tilt the boom suspending the calibration weight; the processor deriving a second parameter change amount, which is a change amount of the variable parameter after the second guidance is notified; the processor deriving a second lifting load, which is the lifting load when the second parameter change amount represents an erecting operation or a tilting operation of the boom; The processor derives a first correction parameter, which is part of the correction parameters and relates to correction of the hanging load when the pressure loss is 0, by comparing the first hanging load with a preset calibration load; the processor deriving a second correction parameter relating to the pressure loss, the second correction parameter being part of the correction parameter, by comparing the calibration load with the second hanging load; The method for deriving a suspension load according to claim 1 , wherein the processor derives the suspension load using the first correction parameter and the second correction parameter when the adjustment mode is not selected.

8. a boom that is supported so as to be able to rise and fall and that is capable of lifting a load; a hydraulic device including a hydraulic cylinder that raises and lowers the boom; a head pressure detection device for detecting the head pressure of the hydraulic cylinder; a rod pressure detection device for detecting the rod pressure of the hydraulic cylinder; a boom angle detection device for detecting the angle of the boom; A crane comprising: a processor that derives the lifting load of the boom by the lifting load deriving method according to any one of claims 1 to 3.

9. the processor derives a limit load based on a plurality of boom-related parameters including the detection value of the boom angle detection device; The crane according to claim 8 , wherein the processor further executes an overload prevention process including a process of outputting an alarm when the derived lifting load exceeds the limit load.

10. A method for deriving a lifting load of a boom in a crane that raises and lowers a boom by a hydraulic cylinder, comprising: a processor, when a change in a variable parameter representing the boom hoisting operation represents a stopped state of the boom or an erecting operation of the boom, deriving the lifting load based on the detected values ​​of the head pressure and rod pressure of the hydraulic cylinder and the detected value of the boom angle, and updating the lifting load to the derived value; The processor maintains the lifting load without updating it when the change in the variable parameter represents a tilting operation of the boom.

11. a boom that is supported so as to be able to rise and fall and that is capable of lifting a load; a hydraulic device including a hydraulic cylinder that raises and lowers the boom; a head pressure detection device for detecting the head pressure of the hydraulic cylinder; a rod pressure detection device for detecting the rod pressure of the hydraulic cylinder; a boom angle detection device for detecting the angle of the boom; A crane comprising: a processor that derives the lifting load of the boom by the lifting load deriving method according to claim 10.

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