High-speed crane with light load

Abstract

To provide a crane that performs high-speed operation using remaining power of a motor during acceleration time light load, in which the crane shortens a braking distance from high-speed operation to improve safety of high-speed operation during light load, and expands a range allowing speed control that increases speed from rated speed to high speed, thereby making it possible to further shorten cargo handling and transportation time.SOLUTION: A crane that is provided with a high-speed operation function of hoisting speed during light load that rotates at high speed to a rotation speed region that exceeds a rated rotation speed where a torque of a hoisting motor decreases when the load lifted by the crane is light compared to a rated load of the crane, and when decelerating from a high-speed rotation state during the light load, a deceleration rate is changed briefly according to the torque of the hoisting motor recovering and increasing as the rotation speed of the hoisting motor decreases.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a technique for increasing the hoisting speed of a crane by utilizing the excess power generated in a hoisting motor to rotate the motor beyond the rated rotation speed when the load hoisted by the crane is light. [Background technology]

[0002] A crane's hoisting device is able to hoist heavy loads into the air with a relatively small force by slowing down the hoisting speed using a reducer with a high reduction ratio and by using a number of wire ropes hung on the sheaves.By rolling the iron wheels on the traversing or running iron rails, it is an efficient loading and transporting machine that can move horizontally with little force. However, because the speed of the hoisting device is slow, when no cargo is being lifted or when the cargo is light in weight, no hoisting force is required, but the hoisting speed is slow, taking a long time to operate, and there is a problem that it is not time-efficient. Technologies have been proposed to increase the hoisting speed above the rated speed by utilizing the surplus motor power generated when the cargo is not being lifted or the load is light, thereby shortening the cargo-handling and transportation time and improving time efficiency (see, for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 60-219999 [Patent Document 2] Japanese Patent Application Publication No. 4-66498 [Patent Document 3] Public Relations, Patent Publication No. 7-187565 Summary of the Invention [Problem to be solved by the invention]

[0004] By the way, when no cargo is being lifted or the load is extremely light, the hoisting speed can be three or four times the rated speed, if we only consider the motor's spare power and load. However, if the motor is actually rotated at a speed far exceeding the rated speed, a large centrifugal force acts on the rotating parts of the motor, such as the rotor. Also, the hoisting brake for holding the load is also a sliding brake. The speed of the moving surface becomes too fast, causing a decrease in friction and problems such as vibration and noise, so currently high-speed operation under light load is limited to about twice the rated speed, and it is not possible to go any faster than that.

[0005] In addition, the braking distance during high-speed operation under a light load is the square of the braking distance at the rated speed, so if the speed during high-speed operation under a light load is increased to twice the rated speed, the braking distance will be four times the braking distance at the rated speed, and if the speed is increased by more than twice the rated speed, up to three times the rated speed, the braking distance will be nine times, which can cause problems in operability and pose a danger. Therefore, Patent Document 3 describes a technology for shortening the braking distance by increasing the deceleration above the rated speed. However, since the output torque of the motor decreases above the rated speed, in order to realize the technology described in Patent Document 3, it is necessary to use a large-capacity motor and inverter, which poses a cost issue.

[0006] In view of the problems with the conventional cranes described above, an object of the present invention is to provide a crane that operates at high speeds by using the spare power of the motor when the load is light during acceleration, shortening the braking distance from high speed operation and improving the safety of high speed operation under light load, while widening the range in which speed control is possible to increase the speed from the rated speed to a high speed, thereby further shortening the time required for loading and unloading. [Means for solving the problem]

[0007] In order to achieve the above object, the high-speed operation crane under light load of the present invention is a crane equipped with a high-speed operation function for a hoisting speed under light load, which rotates the crane at high speed up to a rotation speed range exceeding the rated rotation speed where the torque of the hoisting motor decreases when the load lifted by the crane is lighter than the rated load of the crane, and when decelerating from the high-speed operation state under light load, the deceleration rate is increased in accordance with the torque of the hoisting motor recovering and increasing as the rotation speed of the hoisting motor decreases. To a large value The present invention is characterized in that the above-mentioned is changed. In other words, when the motor exceeds its rated speed due to high-speed operation under light load and is rotating in a speed range where the motor generated torque is decreasing, if the motor is decelerated from that state, the motor generated torque will recover and increase as the rotation speed decreases. To a large value By varying this, it is possible to shorten the braking distance without increasing the capacity of the motor or inverter, solving the problem of long braking distance during high-speed operation under light load.

[0008] In this case, Large value When decelerating at a deceleration rate, the deceleration rate is changed just before the deceleration ends and the motor stops. Change to a smaller value By adding this function, the deflection of the crane girder caused by the force of sudden deceleration is slowly returned to its original position just before the crane comes to a stop, reducing the vibration of the girder after the crane has stopped, and thereby suppressing the vertical vibration of the suspended load after the crane has stopped.

[0009] In addition, when accelerating the hoisting motor under light load, the acceleration rate is increased by using the motor's surplus power. Large value and accelerating, and as the rotation speed of the motor exceeds the rated rotation speed, the torque that the hoisting motor can output decreases, Large value The acceleration rate set in the Change to a smaller value By doing so, it is possible to add a function of accelerating in a short time.

[0010] Also, when accelerating immediately after starting, Small valueAccelerate at the acceleration rate, then change the acceleration rate Change to a larger value This allows the deflection of the crane girder that occurs during acceleration to occur slowly, reducing the vibration of the girder after starting and suppressing up and down vibration during operation.

[0011] In addition, the acceleration time can be lengthened when accelerating the winding up, and the acceleration time can be shortened when accelerating the winding down, and the deceleration time can be shortened when decelerating the winding up, and the deceleration time can be lengthened when decelerating the winding down.

[0012] In addition, by setting a torque limit value so as not to exceed the maximum output torque value of the hoisting motor and setting the acceleration or deceleration time to the shortest time, it is possible to accelerate in a short time using the remaining power of the hoisting motor when accelerating under a light load, and to decelerate in a short time according to the motor torque so that the rotation speed of the hoisting motor decreases due to deceleration and increases as it recovers.

[0013] In addition, by using a motor with a low rated rotation speed for the hoisting motor, specifically a multi-pole motor with a low rated rotation speed or a low-rotation AC motor with a low frequency as a rated power source for the hoisting motor, the speed output range for high-speed operation under light load can be widened. In other words, by using a low-speed, high-torque motor for the hoisting motor, it is possible to eliminate the high-speed rotating parts from the rotating parts of the hoisting device and solve the effect of centrifugal force on the strength of the high-speed rotating parts, making it possible to increase the speed under light load to higher speeds than before. Effect of the Invention

[0014] According to the high-speed operation crane under light load of the present invention, during the crane's cargo handling and transporting process, when the crane is operating at high speed under light load when the motor load is small due to empty operation or when the suspended load is extremely light, the problems of increased centrifugal force in the rotating parts and longer braking distance that previously occurred when operating at high speed are solved, making it possible to increase the speed faster than before, thereby providing a highly efficient crane that significantly shortens the time required for cargo handling and transporting operations. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is an explanatory diagram of a typical crane transport process. [Diagram 2] FIG. 4 is an explanatory diagram of the output torque characteristics of a motor. [Diagram 3] FIG. 1 is an explanatory diagram of a hoisting device with an expanded speed range for high-speed operation under light load. [Figure 4] FIG. 1 is an explanatory diagram of the maximum speed that can be outputted relative to the load factor of a crane. [Diagram 5] FIG. 2 is an explanatory diagram of a deceleration curve in a high-speed operation crane under a light load according to the present invention. [Figure 6] FIG. 2 is an explanatory diagram of an acceleration curve in a high-speed operation crane under a light load according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, a high-speed operation crane under light load according to the present invention will be described based on an embodiment with reference to the drawings.

[0017] Figure 1 shows a diagram of a typical crane transport process. When a crane CR transports a cargo CA, there is a calling process CL where the crane CR moves to the cargo CA while empty.Then, the cargo CA is sling-loaded, hoisted by the crane CR, and the crane CR transports the cargo CA to its destination while loaded through a transport process TP, where the cargo CA is transported to its destination. After the sling is released at the destination, the crane CR moves again empty to the location of another cargo CA, or moves to a waiting location for a storage process RT. As described above, in addition to the transport process TP in which the cargo CA is hoisted, the crane transport process always includes a high proportion of empty processes such as the calling process CL and the storing process RT. Therefore, shortening the time for the empty process by operating at high speed under light load is effective in improving the efficiency of the transport work.

[0018] When a load value M is hoisted by a crane CR at a speed V, the hoisting load torque Th applied to the hoisting device at a rotation speed N at the speed V is as shown in equation (1). Th=(M×V)÷(2×π×N)...Equation (1) Here, π is the constant of the circumference of a circle. As shown in formula (1), when the load value M is small, the hoisting load torque Th applied to the hoisting motor is proportionally small. In other words, in the calling process CL and the storing process RT, where the cargo CA is not suspended, the hoisting load torque Th applied to the hoisting motor is nearly zero. Also, in the transportation process TP, the only cranes that always hoist the rated load are some process cranes built into the line. Most cranes are used to hoist light loads, and high-speed operation with light loads is often used effectively. Incidentally, in an inherent hoisting device in which the ratio of the speed V to the number of rotations N in equation (1) is constant (the reduction gear ratio of the machine is constant), even if the number of rotations N and the speed V are changed by controlling the speed of the hoisting motor, the hoisting load torque Th relative to the load value M is constant.

[0019] FIG. 2 shows the motor characteristics of the motor output torque Tm versus the motor rotation speed N when the rotation speed of an AC motor is controlled using a frequency conversion device such as an inverter. The characteristic of a continuous torque CT, which can continuously output 100% rated torque, is that the motor output torque Tm decreases once the rated rotation speed exceeds 100%. At this time, it is necessary to ensure that the hoisting load torque Th does not exceed the continuous torque CT. For this reason, when the load value M is the rated load, which is the maximum load that the crane can hoist, Th is set so that it does not exceed the continuous torque CT when the speed is below 100%, and as the load value M decreases, the speed can be increased accordingly to a speed that does not exceed the continuous torque CT.

[0020] Incidentally, in the case of a six-pole AC motor, when it is rotated by a 50Hz AC power supply, the synchronous speed at 100% rotation is 1000 rotations per minute, and when the power supply frequency is raised to 100Hz, the rotation speed at 200% becomes 2000 rotations per minute. At this time, centrifugal force acts on the rotating parts on the motor shaft, such as the motor rotor and the coupling that connects to the load, in proportion to the square of the rotation speed. This centrifugal force causes strength problems in the high-speed rotating parts, with a rotation speed of about 2000 rotations per minute being the limit. A special structure to give the rotating parts the strength to rotate beyond this is economically inefficient and physically difficult to achieve with the configuration of a typical device. In addition to the strength issues caused by centrifugal force, a rotation speed of 2000 revolutions per minute, which is 200%, reduces the friction of the brake attached to the motor shaft, reducing the holding power of the load, and can also cause problems such as vibration and noise from the reducer.

[0021] In order to solve this problem and achieve a speed output exceeding 200% when the load is light, the hoisting device of the high-speed operation crane under light load of the present invention uses a multi-pole motor DM used in a so-called direct drive system as the hoisting motor as shown in FIG. 3, thereby eliminating the high-speed rotating portion and enabling a speed output of 200% or more when the load is light. For example, if the multi-pole motor DM used in a direct drive system has 30 poles, it will rotate at 200 revolutions per minute when run on a 50 Hz power supply, and even if the rotation speed is increased to 300%, it will only be 600 revolutions per minute, and even at 400%, it will only be 800 revolutions per minute. This prevents the coupling CP and brake BR attached to the motor rotor and motor shaft from becoming weak due to centrifugal force, eliminates problems such as vibration and noise from the reducer GR, and allows the high speed rotation under light load to be increased to even higher speeds.

[0022] Incidentally, when hoisting a crane, even if a 30-pole direct drive multi-pole motor DM is used, if a so-called direct drive is used without a reducer, the hoisting speed of the crane becomes too fast, and the power to hoist a heavy load is insufficient. Therefore, as shown in Figure 3, the power to hoist a heavy load is secured by transmitting the rotational force to the wire drum WD through a one-stage reducer GR. In this way, whereas conventional hoisting reducers for cranes usually have three stages of reduction, this has been reduced to one stage, and a multi-pole motor DM for direct drive is used to keep all axes of the hoisting device at low speeds, preventing problems caused by centrifugal force and other high-speed rotations even when the motor is rotated at speeds significantly exceeding the rated speed when the load is light and the motor load is small.

[0023] Multi-pole motors for direct drive with low rated speeds are generally AC synchronous motors with permanent magnet rotors, but it is also possible to manufacture multi-pole AC induction motors with low rated speeds, which can similarly achieve the effect of light-load, high-speed operation up to high speeds. Also, by manufacturing the motor so that its AC power supply is rated at a low frequency, it is possible to manufacture a motor with a similarly low rated speed, and in this case too, the effect of being able to operate at high speeds with a light load can be obtained.

[0024] Fig. 4 is an explanatory diagram of the maximum speed that the hoisting device can output for the load value M hoisted by the crane. As shown in Fig. 4, when the load value M hoisted by the crane is 100% of the rated load, the combination of the machines is set so that the hoisting load torque Th is equal to the motor's continuous torque CT, and the speed V is controlled so that 100% of the rated speed is output. As the load value M being hoisted becomes lighter, the speed that the motor can output becomes faster, and conventionally, the motor was controlled to increase its rotation speed to 200% of the rated speed when the load value was 25% of the rated load, and a speed limit was imposed so that the speed would not exceed 200% of the rated speed even with a load lighter than 25%. In the high-speed operation crane under light load of the present invention, by restricting all axes of the hoisting device to slow rotation, when the load being hoisted is extremely light or when no load is being hoisted, the motor rotation speed N is increased to 300% or 400% of the rated rotation speed, making it possible to output a hoisting speed of 300% or 400%, a high speed under light load.

[0025] Here, the torque required when accelerating from a stop to the rotation speed Na or when decelerating from the rotation speed Na to a stop in the acceleration / deceleration time ta is the acceleration / deceleration torque Ta shown in equation (2). Ta=(GD 2 ×Na)÷(375×ta) ··· Formula (2) Here, G.D. 2 indicates the moment of inertia. Normally, in inverter control, the short-time torque ST is often set to 150% of the continuous torque CT, as shown in Figure 2. In this case, 100% of the continuous torque CT value is used to supply the hoisting load torque Th, and the remaining 50% of the short-time torque ST is used as the acceleration / deceleration torque Ta. At this time, the value of the acceleration / deceleration time ta is set so that the value of the acceleration / deceleration torque Ta becomes 50%.

[0026] The speed V of the crane's hoisting device is slow, so the moment of inertia caused by the linear movement of the load due to its up and down movement is small. Therefore, the moment of inertia of the high-speed rotating parts such as the hoisting motor, brake, and coupling is the moment of inertia GD of the hoisting device.2 The moment of inertia GD due to the linear movement of the suspended load 2 varies proportionally to the weight of the load, whereas the moment of inertia GD of the rotating parts such as the hoisting motor varies proportionally to the weight of the load. 2 is a fixed value specific to the lifting device and is not affected by the load value M. In other words, the moment of inertia GD 2 The majority of the moment of inertia GD 2 For the hoisting device of a crane, the moment of inertia GD 2 is hardly affected by the load value of the suspended load and is a fixed value specific to the hoisting device.

[0027] Incidentally, when the crane accelerates in the hoisting direction, both the hoisting load torque Th and the acceleration / deceleration torque Ta act as loads on the motor output torque Tm, but when decelerating in the hoisting direction, the hoisting load torque Th and the acceleration / deceleration torque Ta act in opposite directions, so that surplus power is generated in the hoisting motor, and the deceleration time can be shortened. During acceleration in the lowering direction, the hoisting load torque Th and the acceleration / deceleration torque act in opposite directions, so the acceleration time can be set short, but during deceleration in the lowering direction, the hoisting load torque Th and the acceleration / deceleration torque act in the same direction as a load on the motor output torque Tm, so the deceleration time becomes long. The time required for acceleration and deceleration can be improved by lengthening the acceleration time when accelerating in the winding-up direction, shortening the acceleration time when accelerating in the winding-down direction, shortening the deceleration time when decelerating in the winding-up direction, and lengthening the deceleration time when decelerating in the winding-down direction. In this case, however, the braking distance required when decelerating the lowering becomes long, which can lead to the risk of misjudging the start point of deceleration and causing the load to drop forcefully to the floor before it has fully decelerated, so it is necessary to make this as short as possible.

[0028] Here, when decelerating simply at the same deceleration rate from high-speed operation under light load, the braking distance from 200% speed is four times longer than the braking distance when operating at rated speed, the braking distance from 300% speed is nine times longer, and the braking distance from 400% speed is 16 times longer. Even with the conventional high-speed operation under light load limited to a speed of 200%, a braking distance of four times longer was difficult to drive, but exceeding this and reaching a braking distance of nine times longer from a speed of 300% makes it dangerous.

[0029] Therefore, in the light-load high-speed operation of the present invention, if the load value M being lifted is, for example, 10%, the hoisting load torque Th is also 10% of the rated load, so the rotation speed is increased to 300% with the motor's reserve power. Then, when decelerating from that rotation speed N, at the start of deceleration, only the small value remaining after subtracting 10% of the hoisting load torque Th from the value of the motor's short-time torque ST at 300% rotation can be allocated to the acceleration / deceleration torque Ta, so the motor can only output torque for deceleration at the normal deceleration rate. However, after that, as the rotation speed N decreases with deceleration, the short-time torque ST of the motor recovers and increases. At this time, the hoisting load torque Th remains at 10% regardless of the rotation speed, so the value obtained by subtracting 10% of the hoisting load torque Th from the recovered and increased short-time torque ST value can be used as the acceleration / deceleration torque Ta, and the deceleration rate is Large Then, when the rotation speed N is decelerated to 100% rotation speed and the short-time torque ST of the motor at this time is 150%, the remaining 140% after subtracting 10% of the hoisting load torque Th can be allocated to the acceleration / deceleration torque Ta. , braking distance of 、 The acceleration / deceleration torque Ta, which was previously set at 50%, can now be reduced to 1 / 2.8.

[0030] This deceleration curve is shown in the diagram as the shortened braking curve DL in FIG. By decelerating along this shortened braking curve DL, it is possible to decelerate in about half (about 4.5 times) the braking distance for D3 from 300% speed, which was nine times longer than when decelerating along the braking curve D1 from 100% speed, and it is possible to make the braking distance closer to the braking distance for the braking curve D2 from 200%.This expands the control range of high-speed driving under light load up to 300% speed with the same braking distance as high-speed driving under light load with a speed limit added at 200%, while suppressing a significant increase in braking distance and preventing an increase in danger due to higher speeds.

[0031] However, when trying to maximize the motor's capacity and decelerate in a short time, the reaction force of the deceleration force at that time is generated as a deflection of the crane girder, and if the crane is decelerated to a stop at the same momentum, the deflection of the crane girder disappears instantly, causing the crane girder to oscillate up and down after the crane has stopped. As a result, the suspended load vibrates up and down, which hinders precise positioning and stopping. Therefore, in order to suppress the up and down oscillation of the crane girder, the deceleration rate is set to 0.05 at the end of the deceleration of the shortened braking curve DL just before the crane stops. Change to a smaller value By slowly returning the deflection of the crane girder during deceleration while stopping it, the up and down amplitude of the crane girder after stopping can be suppressed, making it easier to precisely position and stop the crane, and providing a crane with good operability.

[0032] On the other hand, when accelerating, it is safer to accelerate slowly along the acceleration curve A1 shown in Figure 6, so there is little need for sudden acceleration. However, in applications where the transportation time must be shortened, the acceleration characteristics of the shortened acceleration curve AL are provided when the load is light, so that high-speed operation at light load can be achieved in a short time. This can shorten the transportation time. The shortened acceleration curve AL is a curve that shows that when the load is light, the hoisting load torque Th becomes smaller, so that the torque obtained by subtracting the hoisting load torque Th from the short-time torque ST of the hoisting motor becomes larger. This allows the acceleration / deceleration torque Ta to be large, so that acceleration can be achieved in a short time. As the motor output torque Tm becomes smaller once the motor speed exceeds the rated speed, the acceleration rate becomes gentler. Change to a smaller valueIt follows the characteristics of In addition, at the beginning of the acceleration start Small value Start with the acceleration rate, then increase the acceleration rate Large value This acceleration characteristic at startup can reduce the vertical vibration of the crane girder, especially when starting and stopping repeatedly in a short period of time with inching operation, and improve operability.

[0033] By the way, in order to create the shortened braking curve DL and the shortened acceleration curve AL, a method has been explained in which the acceleration / deceleration rate is changed in accordance with the change in the rotation speed N under the load state based on the load value of the suspended load or the load factor of the motor, etc. However, it is also possible to create curves similar to the shortened braking curve DL and the shortened acceleration curve AL by setting a torque limit value in the curve of the short-time torque ST in Fig. 2 and setting the acceleration / deceleration time to be short. In this case as well, the deceleration rate or acceleration rate at the end of deceleration or the start of acceleration is set to Set it to a smaller value This reduces vibration of the crane girder, improving operability. By the way, this method of creating the shortest acceleration / deceleration curve with torque limit values ​​and short acceleration / deceleration time settings increases the possibility of an overcurrent trip when control deviates unless a control device with good current control characteristics is used. However, motors used for direct drives often use AC servo motors with permanent magnet rotors that have excellent current control characteristics, and high-performance current control allows the torque to be exerted to the very limit of the short-term torque ST curve with torque limit and short acceleration / deceleration times without causing an overcurrent trip, resulting in the optimum torque according to the lifting load and rotation speed. large This allows the vehicle to accelerate and decelerate at an acceleration / deceleration rate of 0.01 m / s, thereby achieving the shortest acceleration and braking distances.

[0034] FIG. 5 shows the shortened braking curve DL, which enables deceleration in approximately half the braking distance required when simply decelerating from a speed of 300%, but the same is true when accelerating to a speed of 400%; whereas simply decelerating would result in a braking distance 16 times that of braking curve D1 from a speed of 100%, the shortened braking curve DL makes it possible to reduce the braking distance to approximately 8 times that distance. However, a braking distance of 8 times is difficult to use with a general crane, and its use is required for cranes with extremely slow rated speeds, cranes with extremely long hoisting distances, inclines for transporting inclined shafts, etc. In such cases, it is necessary to take safety measures such as installing a deceleration limit switch to limit the speed by 400% to prevent danger from occurring due to the long braking distance.

[0035] Incidentally, permanent magnet rotor AC servo motors, which are widely used as direct drive motors, generally have a large short-term torque ST of 200% or 300% compared to the continuous torque CT, and by utilizing this large short-term torque ST, it is possible to accelerate and decelerate in a short period of time. Furthermore, by combining this large short-time torque with acceleration and deceleration on the shortened braking curve DL and the shortened acceleration curve AL, acceleration and deceleration in an even shorter time can be achieved.

[0036] Here, we have described a technology that makes maximum use of the capabilities of the hoisting motor to accelerate and decelerate in a short period of time. However, at the same time, this accumulates repeated stress on the motor structure, the reducer, the keys and other mechanical parts, and the power semiconductors of the control device, so it is necessary to design with a margin that takes into consideration the lifespan of the relevant parts.

[0037] The high-speed operation crane under light load according to the present invention has been described above based on the embodiments thereof. However, the present invention is not limited to the configurations described in the above embodiments, and the present invention can be modified without departing from the spirit of the present invention. The configuration can be modified appropriately within the scope. [Industrial Applicability]

[0038] The high-speed operation crane under light load of the present invention solves the problem of the strength of the rotating parts against the centrifugal force caused by high-speed rotation when operating at high speed under light load, and also solves the problem of extended braking distance even when operating at high speed under light load, making the crane safer and easier to handle.It can also be operated up to higher speeds without increasing the motor capacity under light load, thereby shortening the time required for loading and transporting operations and making it highly useful in industry. [Explanation of symbols]

[0039] CR Crane CA cargo handling CL Crane Call Process TP transportation process RT Crane storage process Tm Motor output torque Th Winding load torque Ta Acceleration / deceleration torque N Number of revolutions CT Continuous Torque ST Short-time torque DM Multi-pole Motor CP Coupling BR Brake GR reducer WD Wire Drum SH Sheaves TS Traverse Device M Load Value V speed t time td deceleration time D1 Braking curve (100% speed) D2 braking curve (200% speed) D3 braking curve (300% speed) DL shortening damping curve ta acceleration time A1 acceleration curve AL shortening acceleration curve

Claims

1. In a crane equipped with a high-speed operation function for hoisting and lowering at light loads, which rotates the hoisting motor at high speeds up to a rotational speed range exceeding the rated rotational speed where the torque of the hoisting motor decreases when the load hoisted by the crane is light compared to the rated load of the crane, when decelerating from the high-speed operation state at light loads, the torque of the hoisting motor recovers and increases as the rotational speed of the hoisting motor decreases.

1. A high speed crane for light load operation, characterized in that the deceleration rate is changed to a large value in response to the load.

2. A high-speed operating crane under light load as described in Claim 1, characterized in that a function is added to change the deceleration rate to a small value just before the deceleration ends and the crane stops when decelerating at a large deceleration rate.

3. 3. The high-speed operation crane under light load according to claim 1 or 2, characterized in that, when accelerating the hoisting motor under light load, the acceleration rate is set to a large value using the motor's spare power for acceleration, and as the torque that the hoisting motor can output decreases when the rotation speed of the motor exceeds the rated rotation speed, the acceleration rate that was set to a large value is changed to a small value as the rotation speed increases from the point where the rated rotation speed is exceeded, thereby adding a function of accelerating in a short time.

4. 4. A high speed operation crane under light load according to claim 1, 2 or 3, wherein the acceleration rate is initially small when accelerating immediately after start-up, and then the acceleration rate is changed to a large value.

5. 5. A high speed operation crane under light load according to claim 1, 2, 3 or 4, characterized in that the acceleration time is lengthened when accelerating hoisting, the acceleration time is shortened when accelerating lowering, the deceleration time is shortened when decelerating hoisting, and the deceleration time is lengthened when decelerating lowering.

6. 6. A high-speed operation crane under light load as claimed in claim 1, 2, 3, 4 or 5, characterized in that a torque limit value is set so as not to exceed the maximum output torque value of the hoisting motor, and the acceleration or deceleration time is set to the shortest time, thereby accelerating in a short time using the remaining power of the hoisting motor when accelerating under light load, and decelerating in a short time according to the motor torque so that the rotation speed of the hoisting motor decreases due to deceleration.

7. 7. A crane for high speed operation under light load according to claim 1, 2, 3, 4, 5 or 6, characterized in that a motor having a low rated rotation speed is used as the hoisting motor, thereby widening the speed output range for high speed operation under light load.

Images