Cranes and methods for stopping them

Abstract

To provide a crane capable of reducing energy required for operation, saving a space of a device, and reducing the weight, and a stop method of the crane.SOLUTION: Driving sources 32, 42 include permanent magnet exciting motors 36, 46. The permanent magnet exciting motors 36, 46 can secure the capacity (kW) sufficient for operating a crane 1 with low rotation speed without reducing the rotation speed by using a reducing gear. Accordingly, rotation shafts 34, 44 of driving parts 31, 41 are provided coaxially to output shafts 37, 47 of the permanent magnet exciting motors 36, 46 without through the reducing gear. A space required for the reducing gear can be omitted by omitting the reducing gear. In addition, it is not necessary that the rotation shafts 34, 44 of the driving parts 31, 41 and the output shafts 37, 47 of the motors are arranged to be shifted from one another through the reducing gear. The driving parts 31, 41 can efficiently use driving force from the output shafts 37, 47 of the permanent magnet exciting motors 36, 46.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a crane and a method for stopping a crane. [Background technology]

[0002] Conventionally, there is known a crane equipped with a suspending part that holds an object by suspending it, and a moving part that moves the suspending part horizontally (see, for example, Patent Document 1). In order to move the object to be held to a target position, this crane winds up the wire of the suspending part with a hoisting device, travels with a traveling device, and travels laterally with a traversing device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-216220 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned crane, the drive devices such as the hoisting device, traveling device, and traverse device include a drive unit such as a winding drum and wheels, and a motor that generates drive power for the drive unit. The rotating shaft of the drive unit and the output shaft of the motor are connected via a reducer. As a result, the crane reduces the rotation speed of the motor using the reducer, allowing the drive unit to be driven at a desired speed. However, there has been a demand for cranes that require less energy for operation, are more space-saving, and are lighter in weight.

[0005] The present invention has been made to solve these problems, and has an object to provide a crane and a method for stopping a crane that can reduce energy consumption for operation, save space for the device, and reduce weight. [Means for solving the problem]

[0006] The crane of the present invention has a suspending part that holds an object by suspending it, and moves the suspending part. It is equipped with a drive unit that operates the crane, and a drive source that generates a driving force for the drive unit, and the drive source has a permanent magnet excitation motor, and the rotating shaft of the drive unit is arranged coaxially with the output shaft of the permanent magnet excitation motor.

[0007] In this crane, the drive source that generates the driving force for the drive unit includes a permanent magnet excited motor. This permanent magnet excited motor can ensure sufficient capacity for crane operation at low rotational speeds without using a reducer to reduce its rotational speed. Therefore, the rotating shaft of the drive unit is coaxial with the output shaft of the permanent magnet excited motor without using a reducer. By eliminating the reducer, the space required for the reducer can be saved, and it is no longer necessary to offset the rotating shaft of the drive unit and the output shaft of the motor via a reducer. Furthermore, the drive unit can efficiently use the driving force from the output shaft of the permanent magnet excited motor. As a result, it is possible to reduce the energy required to operate the crane, save space in the device, and reduce its weight.

[0008] The crane includes an electric braking unit that brakes the drive unit by performing control processing to electrically generate a braking force on the permanent magnet excited motor, and a mechanical braking unit that brakes the drive unit by mechanical braking force. The drive unit has a normal stop mode and an emergency stop mode in which it stops more quickly than in the normal stop mode. In the normal stop mode, the drive unit may be stopped using both the electric braking unit and the mechanical braking unit. For example, if the drive unit is braked using only the mechanical braking unit during stopping, there is a possibility that the mechanical braking unit will deteriorate. Therefore, in the normal operation mode, by using not only the mechanical braking unit but also the electric braking unit, deterioration of the mechanical braking unit can be suppressed.

[0009] In the normal stop mode, the mechanical braking unit may start operating after the control process of the electrical braking unit has started. In this case, the mechanical braking unit can apply a mechanical braking force after the electrical braking unit has sufficiently reduced the speed of the drive unit, thereby suppressing deterioration.

[0010] In emergency stop mode, the drive unit may be stopped only by the operation of the mechanical braking unit. In emergency stop mode, the drive unit must be stopped quickly, but if braking is performed suddenly by the electrical braking unit, the heat generated by the permanent magnet excitation motor may increase, which could result in damage. Therefore, by stopping the drive unit quickly only by the operation of the mechanical braking unit, damage to the permanent magnet excitation motor can be reduced.

[0011] The crane may further include a mechanical braking unit that brakes the drive unit by mechanical braking force, and the drive unit may be provided with a flange that extends outward, and the mechanical braking unit may apply braking force to the flange. For example, if a take-up drum or the like originally has a flange, the existing flange can be used as the member to which the mechanical braking unit applies braking force.

[0012] The number of poles of a permanent magnet excitation motor can be more than 10. In this case, sufficient capacity can be ensured at low rotation speeds.

[0013] The method for stopping a crane according to the present invention is a method for stopping a crane that has a suspending part that holds an object by suspending it and that moves the suspending part, wherein the crane is equipped with a drive part that operates the crane and a drive source that generates a drive force for the drive part, and the drive source has a permanent magnet excitation motor and performs control processing to electrically generate a braking force on the permanent magnet excitation motor, thereby braking the drive part.

[0014] According to this method for stopping a crane, the drive source that generates the drive force for the drive unit has a permanent magnet excitation motor. This permanent magnet excitation motor can ensure sufficient capacity for crane operation at a low rotation speed without using a reducer to reduce the rotation speed. In addition, a control process can be performed to electrically generate a braking force for the permanent magnet excitation motor, so that the braking process can be performed to brake the drive unit. [Effects of the Invention]

[0015] According to the present invention, a crane and a method for stopping a crane are provided that can reduce energy consumption for operation, save space for the device, and reduce weight. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic front view of a crane according to an embodiment of the present invention. FIG. [Figure 2] FIG. 2 is a perspective view showing an example of the configuration of a traveling device. [Figure 3] FIG. 2 is a perspective view showing an example of the configuration of a hoisting device. [Figure 4] 10 is a flowchart showing the operation of the crane. [Figure 5] FIG. 10 is a perspective view showing an example of the configuration of a traveling device according to a comparative example. [Figure 6] FIG. 10 is a perspective view showing an example of the configuration of a hoisting device according to a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic front view of a crane 1 according to an embodiment of the present invention. As shown in FIG. 1, the crane 1 is an overhead crane, and is a device that holds an object with a suspending part 6 and moves the suspending part 6 together with the object. Note that the crane 1 is not limited to an overhead crane, and may be a hoist crane, a gantry crane, a jib crane, or the like. The object is also not particularly limited, and various items such as coils, slabs, bundled steel bars, and steel plates may be used.

[0018] As shown in FIG. 1 , the crane 1 includes a rail 2 , a girder 3 , a trolley 4 , a suspension unit 6 , a traveling device 7 , a traverse device 8 , a hoisting device 9 , and a control unit 10 .

[0019] The rails 2 are members that guide the movement of the suspending part 6 in the traveling direction D1 via the girders 3 and the trolley 4. The rails 2 are a pair of guide members that are spaced apart from each other in the lateral direction D2 and extend parallel to the traveling direction D1. The rails 2 are fixed to the ceiling of the building in which the crane 1 is installed. The girders 3 are a pair of members that guide the movement of the suspending part 6 in the lateral direction D2 via the trolley 4. The girders 3 are a pair of guide members that are spaced apart from each other in the traveling direction D1 and extend parallel to the lateral direction D2 so as to be spanned across the pair of rails 2. The girders 3 can travel in the traveling direction D1 along the rails 2 by means of a traveling device 7 described below. The trolley 4 suspends the suspending part 6 while supported by the girders 3. The trolley 4 can travel laterally in the lateral direction D2 along the girders 3 by means of a lateral travel device 8 described below.

[0020] The traveling devices 7 are devices for causing the girder 3 to travel along the rails 2. The traveling devices 7 are provided at both ends of the girder 3 in the lateral direction D2. Each traveling device 7 has wheels 21. The traverse device 8 is a device for causing the trolley 4 to travel lateral along the girder 3. The traverse device 8 has wheels 22 provided on the trolley 4.

[0021] The suspending part 6 holds an object by suspending it. The suspending part 6 is suspended from the trolley 4 by a wire 23. The suspending part 6 is connected to a hoisting device 9 provided on the trolley 4 via the wire 23. Therefore, the hoisting device 9 can lift the suspending part 6 by winding up the wire 23.

[0022] Here, a specific configuration of the traveling device 7 will be described with reference to FIG. 2. FIG. 2 is a perspective view showing an example of the configuration of the traveling device 7. As shown in FIG. 2, the traveling device 7 includes a drive unit 31, a drive source 32, and a mechanical braking mechanism 33. The drive unit 31 is a device that operates the crane 1. The drive unit 31 includes the wheels 21 (see also FIG. 1) and a rotating shaft 34 provided on the wheels 21. The rotating shaft 34 is fixed to the center position of the wheels 21 and extends parallel to the lateral direction D2. The drive source 32 is a device that generates a driving force for the drive unit 31. The drive source 32 includes a permanent magnet excitation motor 36. The permanent magnet excitation motor 36 has an output shaft 37 that extends from the center position toward the drive unit 31. The output shaft 37 extends parallel to the lateral direction D2 and is connected to the rotating shaft 34 of the drive unit 31. Therefore, when the permanent magnet excitation motor 36 rotates, a rotational force is transmitted via the output shaft 37 and the rotating shaft 34, thereby rotating the wheels 21. The relationship between the output shaft 37 and the rotating shaft 34 will be described later.

[0023] The mechanical braking mechanism 33 is a mechanism that brakes the rotation of the drive unit 31 by mechanical braking force. The mechanical braking mechanism 33 has brake pads 33a that can reciprocate in the lateral direction D2. Meanwhile, the drive source 32 is provided with a brake disc plate 38 that is disposed coaxially with the output shaft 37 and rotates in conjunction with the output shaft 37. The mechanical braking mechanism 33 presses the brake pads 33a against the brake disc plate 38, thereby generating a frictional force between the brake pads 33a and the brake disc plate 38 that rotates together with the output shaft 37. This frictional force acts on the brake disc plate 38 as a braking force, thereby slowing down or stopping the rotation of the brake disc plate 38. In this way, the mechanical braking mechanism 33 can apply a mechanical braking force to the drive unit 31 via the brake disc plate 38.

[0024] The traversing device 8 has the same configuration as the traveling device 7, except that the rotation shaft 34 of the drive unit 31 and the output shaft 37 of the permanent magnet excitation motor 36 extend in the traveling direction D1.

[0025] Next, a specific configuration of the hoisting device 9 will be described with reference to FIG. 3. FIG. 3 is a perspective view showing an example of the configuration of the hoisting device 9. As shown in FIG. 3, the hoisting device 9 includes a drive unit 41, a drive source 42, and a mechanical braking mechanism 43. The drive unit 41 is a device that operates the crane 1. The drive unit 41 includes a winding drum 40 that rotates to wind up and down the wire 23, and a rotating shaft 44 provided on the winding drum 40. The rotating shaft 44 is fixed to the center position of the winding drum 40 and extends parallel to the traveling direction D1. The drive source 42 is a device that generates a driving force for the drive unit 41. The drive source 42 includes a permanent magnet excitation motor 46. The permanent magnet excitation motor 46 has an output shaft 47 that extends from the center position toward the drive unit 41. The output shaft 47 extends parallel to the traveling direction D1 and is connected to the rotating shaft 44 of the drive unit 41. Therefore, when the permanent magnet excitation motor 46 rotates, a rotational force is transmitted via the output shaft 47 and the rotating shaft 44, thereby rotating the winding drum 40. The relationship between the output shaft 47 and the rotating shaft 44 will be described later. The direction in which the rotating shaft 44 and the output shaft 47 extend is not particularly limited, and they may extend parallel to the lateral direction D2.

[0026] The mechanical braking mechanism 43 applies a mechanical braking force to the drive unit 41, thereby braking the rotation of the drive unit 41. The mechanical braking mechanism 43 has brake pads 43a that can move back and forth in the traveling direction D1. Meanwhile, the drive unit 41 is provided with a flange 49 that widens toward the outer periphery. The flange 49 is a disk-shaped portion with a diameter larger than that of the take-up drum 40. The flange 49 rotates in conjunction with the take-up drum 40. This flange 49 functions as a brake disc plate 48 for the mechanical braking mechanism 43. The mechanical braking mechanism 43 presses the brake pads 43a against the brake disc plate 48, thereby generating a frictional force between the brake disc plate 48, which rotates together with the take-up drum 40. This frictional force acts on the brake disc plate 48 as a braking force, slowing down or stopping the rotation of the brake disc plate 48. This allows the mechanical braking mechanism 43 to apply a mechanical braking force to the drive unit 41 via the brake disc plate 48. The flange 49 of the winding drum 40 used as the brake disc plate 48 may be an existing flange that is used as the brake disc plate 48 as is, or may have a larger diameter than the existing flange and be used as the brake disc plate 48.

[0027] Next, the permanent magnet excitation motors 36, 46 will be described in detail. A "permanent magnet excitation motor" is a motor that uses a permanent magnet as a rotor. The rotor rotates in synchronization with a rotating magnetic field generated by an AC voltage applied to the stator winding and a permanent magnet. The permanent magnet excitation motors 36, 46 are also called PM (Permanent Magnet) motors. For example, an IPM motor in which a permanent magnet is embedded in the rotor, or an SPM motor in which a permanent magnet is attached to the surface of the rotor, may be used as the permanent magnet excitation motors 36, 46. The number of poles (the number of electromagnets in the stator) of the permanent magnet excitation motors 36, 46 is preferably more than 10 poles, and may be, for example, 20 poles or more, 24 poles or more, or 40 poles or more. Note that there is no particular upper limit on the number of poles.

[0028] Next, the relationship between the rotating shafts 34, 44 of the driving units 31, 41 and the output shafts 37, 47 of the permanent magnet excitation motors 36, 46 will be described. As shown in FIG. 2, the rotating shaft 34 of the driving unit 31 is provided coaxially with the output shaft 37 of the permanent magnet excitation motor 36. As shown in FIG. 3, the rotating shaft 44 of the driving unit 41 is provided coaxially with the output shaft 47 of the permanent magnet excitation motor 46. In this case, the central axes CL1, CL3 of the rotating shafts 34, 44 of the driving units 31, 41 coincide with the central axes CL2, CL4 of the output shafts 37, 47 of the permanent magnet excitation motors 36, 46. The rotating shafts 34, 44 of the driving units 31, 41 and the output shafts 37, 47 of the permanent magnet excitation motors 36, 46 are coupled so that their rotation speeds are the same. That is, the rotating shafts 34, 44 of the drive units 31, 41 rotate at the same rotation speed as the output shafts 37, 47 of the permanent magnet excitation motors 36, 46. Therefore, the rotating shafts 34, 44 of the drive units 31, 41 rotate at the same rotation speed as the output shafts 37, 47 of the permanent magnet excitation motors 36, 46. The coupling members 35, 45 connecting the rotating shafts 34, 44 of the drive units 31, 41 to the output shafts 37, 47 of the permanent magnet excitation motors 36, 46 are fixed to prevent slippage in the rotational direction. Note that, as long as the above relationship is satisfied, the diameter of the rotating shafts 34, 44 of the drive units 31, 41 may be different from the diameter of the output shafts 37, 47 of the permanent magnet excitation motors 36, 46.

[0029] Returning to FIG. 1 , the control unit 10 will be described. The control unit 10 includes a processor, memory, storage, a communication interface, and a user interface, and is configured as a general computer. The processor is a computing device such as a CPU (Central Processing Unit). The memory is a storage medium such as a ROM (Read Only Memory) or a RAM (Random Access Memory). The storage is a storage medium such as a HDD (Hard Disk Drive). The communication interface is a communication device that realizes data communication. The user interface is an output device such as an LCD or a speaker, and an input device such as a control lever, buttons, a keyboard, a touch panel, or a microphone. The processor controls the memory, storage, communication interface, and user interface, and realizes the functions described below. The control unit 10 realizes various functions by, for example, loading a program stored in the ROM into the RAM and executing the program loaded into the RAM with the CPU. The control unit 10 may be composed of multiple computers.

[0030] The control unit 10 is a device that comprehensively controls the entire crane 1. The control unit 10 includes a motor control unit 11 and a braking mechanism control unit 12. The control unit 10 is electrically connected to the traveling device 7, the traverse device 8, and the hoisting device 9, and is capable of receiving various detection signals and transmitting various control signals. The motor control unit 11 is a unit that inverter controls the permanent magnet excitation motors 36, 46 of the traveling device 7, the traverse device 8, and the hoisting device 9.

[0031] The motor control unit 11 includes a drive control unit 13 and an electric braking unit 14. The drive control unit 13 drives the permanent magnet excitation motors 36, 46 of the traveling device 7, the traverse device 8, and the hoisting device 9 at a predetermined speed by transmitting a command value for a predetermined speed to the permanent magnet excitation motors 36, 46.

[0032] The drive control unit 13 performs initial magnetic pole detection when starting operation of the permanent magnet excitation motors 36, 46. As a method for initial magnetic pole detection, the drive control unit 13 may employ a pull-in method in which the rotor is started by a pull-in current, a high frequency superposition method in which a high frequency is applied to the motor to detect the rotor position, or a pulse method in which a pulse signal is input to the motor to detect the rotor position.

[0033] The drive control unit 13 may also use PM PG-less vector control as the control method for the permanent magnet excitation motors 36, 46. This control method can control IPM motors and SPM motors. This control method is a control mode for general variable speed applications that do not require high responsiveness or accurate speed control. The speed control range is 1:20.

[0034] Furthermore, the drive control unit 13 may employ advanced vector control without a PG for PM as the control method for the permanent magnet excitation motors 36, 46. This control method can control IPM motors. This control method is a control mode for general variable speed applications that require high-precision speed control and torque limiting operation. The speed control range is 1:20. When "High frequency superposition selection = Yes" is set, the speed control range becomes 1:100. Note that the speed control range of 1:100 is the instantaneous speed region. For continuous operation, the capacity of the inverter and motor must be adjusted.

[0035] The drive control unit 13 may also employ PM PG vector control as the control method for the permanent magnet excitation motors 36, 46. This control method is capable of controlling PM motors. This control method is a control mode for constant torque applications that require high-precision control. It is also a control mode for general variable speed applications that require fast torque response and high-performance torque control. A speed feedback signal from the motor is required. The speed control range is 1:1500.

[0036] The drive control unit 13 may also employ simple vector control as a control method for the permanent magnet excitation motors 36, 46. This control method can control induction motors and PM motors. This control method can drive the motors with high efficiency using simpler procedures.

[0037] The drive control unit 13 may perform current compensation in the low-speed range (10% of the rated speed). For example, the drive control unit 13 may perform torque compensation when the angle between the magnetic flux of the permanent magnet and the rotating magnetic field is shifted by 90°.

[0038] Since it is theoretically impossible to avoid voltage generation when the motor is coasting, it is acceptable to set the induced voltage so that it does not damage the inverter.

[0039] The electrical braking unit 14 is a unit that brakes the drive units 31, 41 of the traveling unit 7, the traverse unit 8, and the hoisting unit 9 by performing braking processing that electrically generates braking force on the permanent magnet excitation motors of the traveling unit 7, the traverse unit 8, and the hoisting unit 9. That is, in this embodiment, inverter-controllable permanent magnet excitation motors 36, 46 are used for the drive units 31, 41 of the crane 1, so that electrical braking force can be generated by performing braking processing.

[0040] The electrical braking unit 14 can perform DC braking, short-circuit braking, zero-speed control, and combinations of these to generate an electrical braking force. DC braking is a process in which a DC current is passed through the windings of the permanent magnet excitation motors 36, 46, consuming power and generating a braking force on the rotor. Short-circuit braking is a process in which the induced electromotive force generated during motor rotation is short-circuited, causing a current to flow through the windings in the opposite direction to the rotation, generating a braking force on the rotor. Zero-speed control is a process in which the current and speed of the permanent magnet excitation motors 36, 46 are controlled to maintain the rotational speed of the permanent magnet excitation motors 36, 46 at zero speed, i.e., to stop the output shaft of the permanent magnet excitation motors 36, 46. Zero-speed control maintains the output shaft of the permanent magnet excitation motors 36, 46 in a stopped state even when an external force is applied to the output shaft. The electrical braking unit 14 sets the frequency at which DC braking starts, and when the frequency drops below the set value, passes a preset DC current through the permanent magnet excitation motor 36, 46 for a preset time. The electrical braking unit 14 sets the frequency at which short circuit braking starts, and when the frequency drops below the set value, performs short circuit braking for a preset time, and when short circuit braking is complete, performs DC braking for the preset time. The electrical braking unit 14 sets the frequency at which zero speed control starts, and when the frequency drops below the set value, performs zero speed control for a preset time.

[0041] Note that even if the drive control unit 13 outputs a command value for a speed lower than the current speed, which results in a decrease in the speed of the permanent magnet excitation motors 36, 46, this process does not result in deceleration by generating a braking force. Therefore, the control process for deceleration by speed control does not fall under the category of braking process for generating an electrical braking force.

[0042] The brake mechanism control unit 12 is a unit that controls the mechanical brake mechanisms 33, 43 of the traveling device 7, the traversing device 8, and the hoisting device 9. The brake mechanism control unit 12 switches the brake pads 33a, 43a between contact and non-contact with the brake disc plates 38, 48 by sending control signals to the mechanical brake mechanisms 33, 43. The mechanical brake mechanisms 33, 43 may be hydraulic mechanisms or electromagnetic mechanisms. As described above, the combination of the brake mechanism control unit 12 and the mechanical brake mechanisms 33, 43 constitutes a mechanical brake unit 50 that brakes the drive units 31, 41 by mechanical braking force.

[0043] Next, the control details when the crane 1 is stopped will be explained. Note that stopping the crane 1 here means that any one of the traveling device 7, the traversing device 8, and the hoisting device 9 is stopped, and it is not necessary that all of the traveling device 7, the traversing device 8, and the hoisting device 9 are stopped. Stopping the drive units 31 of the traveling device 7 and the traversing device 8 means that the rotation of the wheels 21, 22 is stopped. Stopping the hoisting device 9 means that the operation of the winding drum is stopped, and the operation of the suspending unit 6 is stopped.

[0044] The drive units 31, 41 have a normal stop mode and an emergency stop mode. That is, the control unit 10 stops the drive units 31, 41 in either the normal stop mode or the emergency stop mode. The emergency stop mode is a stop mode that requires a quicker stop than the normal stop mode. For example, the emergency stop mode is selected when the operation of the crane 1 needs to be stopped quickly in the event of an operator pressing the emergency stop button or a malfunction of equipment related to the operation of the crane 1 (such as a major hoisting malfunction). The normal stop mode is selected in cases other than the emergency stop mode. For example, the normal stop mode is selected when the operation of the crane 1 is stopped in accordance with an operator's instruction or stop control in automatic operation.

[0045] In the normal stop mode, the drive units 31, 41 are stopped by using both the electric brake unit 14 and the mechanical brake unit 50. That is, in the normal stop mode, the control unit 10 stops the drive units 31, 41 through cooperation between the electric brake unit 14 and the brake mechanism control unit 12. For example, in the normal stop mode, the mechanical brake unit 50 starts operating after the control process of the electric brake unit 14 starts. In this case, the electric brake unit 14 starts the braking process to decelerate the drive units 31, 41 to a certain speed, and then the mechanical brake unit 50 completely stops the drive units 31, 41 by mechanical braking force.

[0046] In emergency stop mode, the drive units 31, 41 are stopped only by the operation of the mechanical braking unit 50. When the control unit 10 detects an abnormality in the crane 1, the drive units 31, 41 are immediately stopped by the mechanical braking force of the mechanical braking unit 50, without performing control processing by the electrical braking unit 14. For example, if hydraulic brakes are used as the mechanical braking mechanisms 33, 43, the mechanical braking unit 50 normally keeps the main circuit turned on to operate the solenoid valve and separate the brake pads 33a, 43a from the brake disc plates 38, 48, and when the emergency stop mode is entered, the main circuit is immediately turned off to stop the operation of the solenoid valve and press the brake pads 33a, 43a against the brake disc plates 38, 48.

[0047] Next, the operation of the crane 1 will be described with reference to FIG. 4. FIG. 4 is a flowchart showing the operation of the crane 1. The control processing shown in FIG. 4 is executed by the control unit 10. Note that, although the operation of the hoisting device 9 will be described here as an example, similar processing is also performed in the traveling device 7 and the traversing device 8. First, the control unit 10 performs processing for preparing to start operation (step S110). In S110, the control unit 10 turns on the inverter power supply for the permanent magnet excitation motor 46 of the hoisting device 9. The drive control unit 13 performs initial magnetic pole detection, turns on an operation command, and detects the output frequency. Furthermore, the brake mechanism control unit 12 releases the mechanical brake mechanism 43.

[0048] Next, the drive control unit 13 outputs a speed command for an arbitrary speed to the permanent magnet excitation motor 46, thereby operating the permanent magnet excitation motor 46 at the arbitrary speed (step S120). Then, the control unit 10 determines whether the operation command is OFF (step S130). If it is determined in step S130 that the operation command is not OFF, the control unit 10 repeats the process from step S120.

[0049] On the other hand, if it is determined in step S130 that the operation command is OFF, the control unit 10 determines whether the stop is a normal stop (step S140). At this time, the control unit 10 makes the determination by detecting the state of the stop button pressed by the worker, the falling speed of the hanging part 6, etc.

[0050] If it is determined in step S140 that the drive unit 41 is in a normal stop state, the drive control unit 13 decelerates the drive unit 41 for a set deceleration time to stop the drive unit 41 in the normal stop mode (step S150). Next, when the drive unit 41 has decelerated to a predetermined speed (or when a predetermined time has elapsed), the electrical braking unit 14 performs control processing to electrically generate a braking force on the permanent magnet excitation motor 46, thereby braking the drive unit 41 (step S160). Next, when the drive unit 41 has decelerated to a predetermined speed (or when a predetermined time has elapsed), the braking mechanism control unit 12 controls the mechanical braking mechanism 43 to brake the drive unit 41 by a mechanical braking force (step S170). As a result, the drive unit 41 stops, and the control processing shown in FIG. 4 ends.

[0051] On the other hand, if the control unit 10 determines in step S140 that the normal stop is not being performed, it performs emergency stop processing to stop the drive unit 41 in emergency stop mode (step S180). The braking mechanism control unit 12 immediately controls the mechanical braking mechanism 43 to brake the drive unit 41 by mechanical braking force (step S190). As a result, the drive unit 41 stops, and the control processing shown in FIG. 4 ends.

[0052] Next, the functions and effects of the crane 1 and the method for stopping the crane 1 according to this embodiment will be described.

[0053] First, referring to FIGS. 5 and 6, a traveling device 7 and a hoisting device 9 of a crane according to a comparative example will be described. As shown in FIG. 5, an induction motor such as a squirrel-cage motor is used as the motor 136 of the traveling device 7 of the crane according to the comparative example, rather than a permanent magnet excitation motor. In this case, to ensure the capacity (kW) required to operate the crane 1, a reducer 135 must be provided between the rotating shaft 34 of the drive unit 31 and the output shaft 37 of the motor 136. In this case, the central axis CL1 of the rotating shaft 34 and the central axis CL2 of the output shaft 37 are arranged eccentrically with respect to each other. As shown in FIG. 6, a squirrel-cage motor is also used as the motor 146 in the hoisting device 9, and therefore a reducer 145 must be provided between the rotating shaft of the drive unit 41 and the output shaft of the motor 146. In this case, the central axis CL3 of the rotating shaft and the central axis CL4 of the output shaft are arranged eccentrically with respect to each other.

[0054] In contrast, in the crane 1 according to this embodiment, the drive sources 32, 42 that generate the drive force of the drive units 31, 41 include permanent magnet excitation motors 36, 46. These permanent magnet excitation motors 36, 46 can ensure sufficient capacity (kW) for operating the crane 1 at low rotational speeds without using a speed reducer to reduce the rotational speed. Therefore, the rotating shafts 34, 44 of the drive units 31, 41 are coaxial with the output shafts 37, 47 of the permanent magnet excitation motors 36, 46 without a speed reducer. Eliminating the need for a speed reducer not only eliminates the need to offset the rotating shafts 34, 44 of the drive units 31, 41 from the motor output shafts 37, 47 via a speed reducer, but also allows the drive units 31, 41 to efficiently use the drive force from the output shafts 37, 47 of the permanent magnet excitation motors 36, 46. As a result, the energy required for operating the crane 1 can be reduced, and the device can be made more compact and lighter. In addition, it is possible to reduce the cost of maintaining the reducer.

[0055] The crane 1 includes an electric braking unit 14 that brakes the drive units 31, 41 by performing control processing to electrically generate braking force on the permanent magnet excitation motors 36, 46, and a mechanical braking unit 50 that brakes the drive units 31, 41 by mechanical braking force. The drive units 31, 41 have a normal stop mode and an emergency stop mode in which they stop more quickly than in the normal stop mode. In the normal stop mode, the drive units 31, 41 may be stopped using both the electric braking unit 14 and the mechanical braking unit 50. For example, if the drive units 31, 41 are braked using only the mechanical braking unit 50 when stopping from a relatively high-speed operation, deterioration of the brake pads 33a, 43a of the mechanical braking unit 50 may occur. Therefore, in the normal operation mode, not only the mechanical braking unit 50 but also the electric braking unit 14 is used to suppress deterioration of the brake pads 33a, 43a of the mechanical braking unit 50.

[0056] In the normal stop mode, the mechanical braking unit 50 may start operating after the start of the control process of the electrical braking unit 14. In this case, the mechanical braking unit 50 can apply a mechanical braking force after the electrical braking unit 14 has sufficiently reduced the speed of the drive units 31, 41, thereby suppressing deterioration of the brake pads 33a, 43a.

[0057] In the emergency stop mode, the drive units 31, 41 may be stopped only by the operation of the mechanical braking unit 50. In the emergency stop mode, the drive units 31, 41 must be stopped quickly, but if braking is performed suddenly by the electrical braking unit 14, the heat generation of the permanent magnet excitation motors 36, 46 may increase, potentially causing damage. Therefore, by quickly stopping the drive units 31, 41 only by the operation of the mechanical braking unit 50, damage to the permanent magnet excitation motors 36, 46 can be reduced.

[0058] The crane 1 further includes a mechanical braking unit 50 that brakes the drive units 31, 41 by mechanical braking force, and the drive units 31, 41 are provided with flanges 49 that extend outward, and the mechanical braking unit 50 may apply a braking force to the flanges 49. For example, if the take-up drum 40 or the like is originally provided with a flange 49, the existing flange 49 can be used as a member to which the mechanical braking unit 50 applies a braking force.

[0059] The number of poles of the permanent magnet excitation motors 36, 46 may be greater than 10. In this case, sufficient capacity can be ensured at low rotation speeds.

[0060] The method for stopping a crane according to this embodiment has a suspending part 6 that holds an object by suspending it, and is a method for stopping a crane that moves the suspending part 6, in which the crane 1 is equipped with drive parts 31, 41 that operate the crane 1, and drive sources 32, 42 that generate drive forces for the drive parts 31, 41, and the drive sources 32, 42 have permanent magnet excitation motors 36, 46, and perform control processing to electrically generate braking forces for the permanent magnet excitation motors 36, 46, thereby braking the drive parts 31, 41.

[0061] According to this method for stopping the crane 1, the drive sources 32, 42 that generate the drive force of the drive units 31, 41 have permanent magnet excitation motors 36, 46. These permanent magnet excitation motors 36, 46 can ensure sufficient capacity for operating the crane 1 at low rotation speeds without the need to reduce the rotation speed using a reducer. In addition, because control processing for electrically generating a braking force for the permanent magnet excitation motors 36, 46 is possible, the braking processing can be performed to brake the drive units 31, 41.

[0062] The present invention is not limited to the above-described embodiments.

[0063] For example, the configuration of the crane described above is merely an example and may be modified as appropriate without departing from the spirit of the present invention. Furthermore, the configurations of the components shown in Figures 2 and 3 are merely an example and may be modified as appropriate. [Explanation of symbols]

[0064] 1...crane, 14...electrical braking unit, 31, 41...drive unit, 32, 42...drive source, 34, 44...rotating shaft, 36, 46...permanent magnet excited motor, 37, 47...output shaft, 49...flange portion, 50...mechanical braking unit.

Claims

1. A crane having a suspending part that holds an object by suspending it and moves the suspending part, a drive unit that operates the crane; a drive source that generates a driving force for the drive unit and has a permanent magnet excitation motor; an electric braking unit that brakes the drive unit by performing control processing to electrically generate a braking force on the permanent magnet excitation motor, a rotation shaft of the drive unit is provided coaxially with an output shaft of the permanent magnet excitation motor, The electric braking unit performs zero speed control to set the rotational speed of the permanent magnet excitation motor to zero as a braking process for generating an electric braking force.

2. The electrical braking unit performs the following braking process to generate an electrical braking force: DC braking in which a DC current is passed through the windings of the permanent magnet excitation motor; or and performing at least one of short-circuit braking to short-circuit the induced electromotive force generated during rotation of the permanent magnet excitation motor. The crane according to claim 1 , wherein the zero speed control is performed when the frequency becomes equal to or lower than a predetermined frequency.

3. The electrical braking unit performs the following braking process to generate an electrical braking force: performing the short-circuit braking; The DC braking is performed at a timing when the frequency becomes equal to or lower than the frequency at which the DC braking is started. The crane according to claim 2 , wherein the zero speed control is performed at a timing when the frequency becomes equal to or lower than a predetermined frequency.

4. a mechanical braking unit that brakes the drive unit by a mechanical braking force, the drive unit has a normal stop mode and an emergency stop mode in which the drive unit stops more quickly than in the normal stop mode, The crane according to claim 2 or 3, wherein in the normal stop mode, the drive unit is stopped by using both the electrical brake unit and the mechanical brake unit.

5. The crane according to claim 4, wherein in the normal stop mode, the mechanical brake unit starts operating after the control process of the electrical brake unit starts.

6. 6. The crane according to claim 4 or 5, wherein in the emergency stop mode, the drive unit is stopped solely by operation of the mechanical brake unit.

7. a control unit for controlling the crane, The crane according to claim 4 or 5, wherein the control unit, when determining that the stop is not a normal stop, performs emergency stop processing to stop the drive unit in the emergency stop mode.

8. Further provided is a mechanical braking unit that brakes the drive unit by a mechanical braking force, The drive unit is provided with a flange that expands toward the outer periphery, The crane according to any one of claims 1 to 7, wherein the mechanical braking portion applies a braking force to the flange portion.

9. The crane according to any one of claims 1 to 8, wherein the number of poles of the permanent magnet excited motor is greater than 10.

10. A method for stopping a crane that has a suspending part that holds an object by suspending it and moves the suspending part, The crane includes a drive unit that operates the crane; a drive source that generates a drive force for the drive unit, the drive source has a permanent magnet excitation motor, performing a control process to electrically generate a braking force on the permanent magnet excitation motor, thereby braking the drive unit; The control process includes: A method for stopping a crane, comprising zero speed control for setting the rotational speed of the permanent magnet excited motor to zero.

Images