CN212863919U - Lifting mechanism of tower crane and tower crane - Google Patents

Abstract

The embodiment of the application provides a lifting mechanism of a tower crane and the tower crane. The hoisting mechanism of the tower crane comprises a hoisting motor, a frequency converter, a steel wire rope, a lifting hook, a signal comparison circuit and a signal sending circuit, wherein the hoisting motor is connected with the steel wire rope and drives the steel wire rope to wind or unwind, and the lifting hook is arranged on the steel wire rope and moves upwards or downwards along with the winding or unwinding of the steel wire rope; the frequency converter is respectively electrically connected with the lifting motor and a torque sensor arranged on the lifting motor, and receives a torque electric signal of the lifting motor from the torque sensor; the frequency converter sends torque electric signals of the lifting motor in a first time period and a second time period to the signal comparison circuit, the signal comparison circuit compares the torque electric signals and sends a comparison result to the signal sending circuit, and the signal sending circuit sends a speed reduction electric signal according to the comparison result. The lifting mechanism makes the heavy object more stable to lift off the ground.

Description

Lifting mechanism of tower crane and tower crane

Technical Field

The embodiment of the application relates to the field of hoisting equipment, in particular to a hoisting mechanism of a tower crane and the tower crane.

Background

With the rapid development of economy and the popularization of new technologies of assembly type buildings, the tower crane is more and more widely applied to the field of infrastructure. The tower crane has the working characteristics of large load of heavy objects, high lifting height, large turning radius, more work in dense personnel areas and the like, so that the requirement on the working safety of the tower crane is higher.

The existing heavy objects lifted by the tower crane are mostly irregular objects such as steel bars, precast slabs and the like, so that the heavy objects are shaken due to unstable gravity center when being lifted off the ground, and further the suspension arm (namely, the rotary big arm) of the tower crane swings up and down to cause danger. The existing tower crane can only depend on the experience of drivers to inhibit the shaking of heavy objects when the heavy objects are lifted off the ground, so that the lifting safety can not be ensured, and the lifting efficiency is lower.

SUMMERY OF THE UTILITY MODEL

In order to solve the above problem, embodiments of the present application provide a lifting mechanism of a tower crane and a tower crane, so as to at least partially solve the above problem.

According to a first aspect of the embodiments of the present application, a hoisting mechanism of a tower crane is provided, which includes a hoisting motor, a frequency converter, a steel wire rope, a hook, a signal comparison circuit, and a signal transmission circuit, wherein the hoisting motor is connected to the steel wire rope and drives the steel wire rope to wind or unwind, the hoisting motor is provided with a torque sensor, and the hook is arranged on the steel wire rope and moves up or down along with the winding or unwinding of the steel wire rope; the frequency converter is electrically connected with the lifting motor to drive the lifting motor, electrically connected with the torque sensor and used for receiving a torque electric signal of the lifting motor from the torque sensor; the frequency converter sends torque electric signals of the lifting motor in a first time period and a second time period to the signal comparison circuit, the signal comparison circuit compares that the torque electric signals in the first time period are smaller than the first comparison signal to obtain a first comparison result, the signal comparison circuit compares that the torque electric signals in the second time period are larger than the second comparison signal to obtain a second comparison result, and the signal sending circuit receives the first comparison result and the second comparison result and outputs a speed reduction electric signal for reducing the driving speed of the lifting motor to the frequency converter.

Optionally, the lifting mechanism includes a roller and a band-type brake, the roller is connected to the lifting motor and is driven by the lifting motor to rotate, the band-type brake is disposed outside the roller and has a band-type state for clamping the roller and a brake-off state separated from the roller, the frequency converter sends torque electric signals of the lifting motor at multiple times in a third time period to the signal comparison circuit, the signal comparison circuit compares the torque electric signals at multiple times with a third comparison signal respectively, when the torque electric signals are greater than the third comparison signal, a third comparison result is obtained, and the signal transmission circuit receives the third comparison result and sends the brake-off signal to the band-type brake.

Optionally, the band-type brake comprises a band-type brake clamping piece, a band-type brake transmission assembly and a driving piece, the band-type brake transmission assembly is connected between the band-type brake clamping piece and the driving piece, the driving piece is electrically connected with the signal sending circuit, and the driving piece receives the brake opening signal and moves along the brake opening direction to drive the band-type brake transmission assembly to move so that the band-type brake clamping piece moves to the brake opening state.

Optionally, the band-type brake clamping piece is two, and relative movably sets up, and band-type brake transmission subassembly includes: the driving transmission rack is arranged on one of the two band-type brake clamping pieces; the driven transmission rack is arranged on the other of the two band-type brake clamping pieces; the driving piece is connected with the driving transmission rack and drives the driving transmission rack to move so as to drive the two band-type brake clamping pieces to move to an open state.

Optionally, the lifting mechanism further includes a timer, the timer is connected to the signal sending circuit, when the timing duration of the timer satisfies the set timing duration, the timer sends a trigger signal to the signal sending circuit, and the signal sending circuit receives the trigger signal and outputs an acceleration electrical signal for increasing the driving speed of the lifting motor to the frequency converter.

Optionally, the hoisting mechanism further comprises a switch disposed in the cab of the crane, the switch being connected between the frequency converter and the signal comparison circuit, the switch having a closed position in which the frequency converter is connected to the signal comparison circuit and an open position in which the frequency converter is disconnected from the signal comparison circuit.

Optionally, the lifting mechanism further comprises a switch box, the switch comprises a first portion and a second portion, the first portion is arranged in the switch box, the second portion protrudes out of the top surface of the switch box, a circuit board is arranged in the switch box, the signal comparison circuit and the signal sending circuit are both arranged on the circuit board, and a potting material layer covering the circuit board, the signal comparison circuit and the signal sending circuit is arranged in the switch box.

Optionally, the signal comparison circuit includes a comparator and a comparison signal source, the comparator includes a forward input terminal, a backward input terminal and an output terminal; the forward input end is connected with the frequency converter and receives a torque electric signal in a first time period and a torque electric signal in a second time period which are sent by the frequency converter; the reverse input end is connected with the comparison signal source and receives a first comparison signal sent by the comparison signal source in a first time interval and a second comparison signal sent by the comparison signal source in a second time interval; the output end is connected with the signal transmitting circuit.

According to the utility model discloses an on the other hand provides a tower crane, and it includes body of the tower, rotation mechanism, davit and hoist mechanism, and rotation mechanism sets up on the body of the tower, and the davit sets up on rotation mechanism, and hoist mechanism sets up on the davit, and hoist mechanism is foretell hoist mechanism.

According to the lifting mechanism of the tower crane provided by the embodiment of the application, the lifting motor is used for driving the steel wire rope to wind or unwind, so that the steel wire rope drives the lifting hook to move upwards or downwards, and the lifting or descending of a heavy object is realized. The lifting motor is connected with a torque sensor to detect the torque of the lifting motor in real time. The frequency converter is respectively connected with the torque sensor and the lifting motor and is used for controlling the rotating speed of the lifting motor, so that the torque of the lifting motor can be adjusted. The signal comparison circuit and the signal sending circuit are both connected with the frequency converter, if the torque electric signal in the first time period is compared by the signal comparison circuit and is always smaller than a first comparison signal, the condition that the hoisting motor is in a rope loosening state is indicated, and the signal comparison circuit outputs a first comparison result to the signal sending circuit. If the signal comparison circuit compares that the torque electric signal in the second time interval is always larger than the second comparison signal, the lifting motor is in a loading state, and the signal comparison circuit outputs a second comparison result to the signal sending circuit. At this moment, the lifting motor is in the process of lifting the heavy object off the ground, the situation that the heavy object is stable off the ground is ensured, shaking is reduced, the signal sending circuit sends a speed reduction electric signal to the frequency converter, the frequency converter controls the lifting motor to reduce the rotating speed, and therefore the speed of the heavy object off the ground is reduced, and shaking is reduced.

Drawings

The drawings are only for purposes of illustrating and explaining the present application and are not to be construed as limiting the scope of the present application. Wherein the content of the first and second substances,

FIG. 1 shows a schematic structural diagram of a lifting mechanism of a tower crane according to an embodiment of the present application;

FIG. 2 shows a schematic diagram of the connection of electrical parts in a lifting mechanism of a tower crane according to an embodiment of the present application;

FIG. 3 is a schematic diagram illustrating a state that a tower crane hoists a heavy object according to an embodiment of the application;

FIG. 4 shows a schematic view of a drive assembly in a band-type brake of a lifting mechanism of a tower crane according to an embodiment of the present application;

FIG. 5 shows a schematic view of a tower crane according to an embodiment of the present application;

FIG. 6 shows a pin diagram of a PLC of a tower crane according to an embodiment of the present application.

Description of reference numerals:

10. a lifting mechanism;

11. a hoisting motor;

12. a frequency converter;

13. a wire rope;

14. a hook;

15. a signal transmitting circuit;

16. a roller;

161. a band-type brake clamping piece;

162. a driving transmission rack;

163. a driven transmission rack;

164. a transmission gear;

17. a signal comparison circuit;

18. a torque sensor;

20. a tower body;

30. a swing mechanism;

40. a luffing mechanism.

Detailed Description

In order to more clearly understand the technical features, objects and effects of the embodiments of the present application, specific embodiments of the present application will be described with reference to the accompanying drawings.

Referring to fig. 1 and 2, fig. 1 shows a schematic diagram of a lifting mechanism of a tower crane according to an embodiment of the present invention. Fig. 2 shows a schematic diagram of the connection of the signal comparison circuit, the signal transmission circuit, the frequency converter, the hoisting motor and the torque sensor according to the embodiment of the present invention.

The lifting mechanism of the tower crane of the embodiment comprises a lifting motor 11, a frequency converter 12, a steel wire rope 13, a lifting hook 14, a signal comparison circuit 17 and a signal sending circuit 15, wherein the lifting motor 11 is connected with the steel wire rope 13 and drives the steel wire rope 13 to wind or unwind, the lifting motor 11 is provided with a torque sensor 18, and the lifting hook 14 is arranged on the steel wire rope 13 and moves upwards or downwards along with the winding or unwinding of the steel wire rope 13; the frequency converter 12 is electrically connected with the lifting motor 11 to drive the lifting motor, the frequency converter is electrically connected with the torque sensor 18, and the frequency converter 12 receives a torque electric signal of the lifting motor 11 from the torque sensor 18; the frequency converter 12 sends torque electric signals of the lifting motor 11 in a first time period and a second time period to the signal comparison circuit 17, the signal comparison circuit 17 compares that the torque electric signals in the first time period are smaller than a first comparison signal to obtain a first comparison result, the signal comparison circuit 17 compares that the torque electric signals in the second time period are larger than a second comparison signal to obtain a second comparison result, and the signal sending circuit 15 receives the first comparison result and the second comparison result and outputs a deceleration electric signal for reducing the driving speed of the lifting motor 11 to the frequency converter 12.

A lifting motor 11 of a lifting mechanism 10 of the tower crane is used for driving a steel wire rope 13 to wind or unwind the rope, so that the steel wire rope 13 drives a lifting hook 14 to move upwards or downwards to lift or descend a heavy object. A torque sensor 18 is connected to the hoist motor 11 to detect the torque of the hoist motor 11 in real time. The frequency converter 12 is connected to the torque sensor 18 and the hoisting motor 11, respectively, and is used to control the rotation speed of the hoisting motor 11, thereby implementing the adjustment of the torque thereof. The signal comparison circuit 17 and the signal sending circuit 15 are both connected with the frequency converter 12, if the signal comparison circuit 17 compares that the torque electric signal in the first time period is always smaller than the first comparison signal, it indicates that the hoisting motor 11 is in a rope loosening state, and the signal comparison circuit 17 outputs the first comparison result to the signal sending circuit 15. If the signal comparison circuit 17 compares that the torque electric signal in the second time interval is always greater than the second comparison signal, it indicates that the hoisting motor 11 is in the loading state, and the signal comparison circuit 17 outputs the second comparison result to the signal sending circuit 15. At this time, it is indicated that the hoisting motor 11 is in the process of hoisting the heavy object off the ground, and in order to ensure that the heavy object is stable off the ground and reduce the shaking, the signal sending circuit 15 sends a deceleration electric signal to the frequency converter 12, so that the frequency converter 12 controls the hoisting motor 11 to reduce the rotating speed, and the speed of the heavy object off the ground is reduced, so as to reduce the shaking.

In the present embodiment, the time interval between the first time period and the second time period is smaller than an interval threshold (the interval threshold may be determined according to the rotation speed of the hoist motor 11 or other suitable factors, and the interval threshold may be 100 milliseconds, 500 milliseconds, 1 second, 2 seconds, 5 seconds, 10 seconds, 30 seconds, 1 minute, etc.).

The first comparison signal may be a preset empty hook torque of the hoist motor 11, which is a torque when no weight is hung on the hook 14 or gravity of a weight is not carried, for example, a torque generated by the wire rope 13 and the hook 14.

The second comparison signal may be a preset loading torque, and the loading torque may be determined as needed, and if the load is required to be reduced and shaken in the process of lifting the load over 1 ton, the loading torque may be determined according to 1 ton, so that it is ensured that the rotation speed of the lifting motor 11 can be reduced when the load over 1 ton or 1 ton is lifted, thereby reducing the shake.

In the present embodiment, the signal comparison circuit 17 includes a comparator and a comparison signal source, the comparator includes a positive input terminal, a negative input terminal and an output terminal; the positive input end is connected with the frequency converter 12 and receives the electric torque signal sent by the frequency converter 12 in the first time period and the electric torque signal sent by the frequency converter in the second time period; the reverse input end is connected with the comparison signal source and receives a first comparison signal sent by the comparison signal source in a first time interval and a second comparison signal sent by the comparison signal source in a second time interval; the output terminal is connected to the signal transmission circuit 15.

The comparison signal source may be a part of a circuit or other suitable circuit or device in the PLC (programmable logic controller) that is capable of generating the first comparison signal and the second comparison signal, or the comparison signal source may be an external signal source to which pins of the PLC are connected. The comparison signal source can output a corresponding first comparison signal and a second comparison signal according to preset idle hook torque, loading torque and the like.

The comparator may be of any suitable structure, and may be in the same PLC as the comparison signal source or may be independent of the circuit of the PLC, which is not limited in this embodiment.

The signal transmission circuit 15 may be any suitable circuit. For example, it may be a signal processing circuit based on a profinet network, or may be another circuit, an amplifier circuit connected to the signal comparison circuit 17 and the corresponding pin of the frequency converter 12, or the like.

Optionally, in order to facilitate the operation of the driver, the hoisting mechanism 10 further comprises a switch arranged in the cab of the crane, the switch being connected between the frequency converter 12 and the signal comparison circuit 17, the switch having a closed position in which the frequency converter 12 is connected to the signal comparison circuit 17 and an open position in which the frequency converter 12 is disconnected from the signal comparison circuit 17. Through setting up the switch, the switching-on and switching-off between converter 12 and the signal comparison circuit 17 can conveniently be controlled to the control is whether to control the rotational speed that promotes motor 11, makes it can satisfy navigating mate's demand better.

Optionally, in order to protect the switch and achieve miniaturization and integration, the lifting mechanism 10 further includes a switch box, the switch includes a first portion and a second portion, the first portion is disposed in the switch box, the second portion protrudes out of the top surface of the switch box, a circuit board is disposed in the switch box, the signal comparison circuit 17 and the signal transmission circuit 15 are both disposed on the circuit board, and a potting material layer covering the circuit board, the signal comparison circuit 17 and the signal transmission circuit 15 is disposed in the switch box. The embedment material layer can protect the circuit board on the one hand and the circuit on it, promotes waterproof and insulating nature, and on the other hand can increase the radiating efficiency, avoids the heat accumulation, promotes the security and the reliability of work.

Optionally, in order to facilitate a reliable fixation of the switch box, the bottom of the switch box is provided with a permanent magnet. The switch box is fixed through the magnetic attraction of the permanent magnet, so that the switch box is fixed more conveniently and quickly.

In order to facilitate understanding of the control principle of the lifting mechanism during the process of lifting a heavy object off the ground, the structure of the tower crane and the process of lifting the heavy object are described as follows:

as shown in fig. 5, the tower crane includes a tower body 20, a swing mechanism 30, a luffing mechanism 40, and a lifting mechanism 10. The swing mechanism 30 is arranged at the top end of the tower body 20, the luffing mechanism 40 is arranged on the swing mechanism 30, and the lifting mechanism 10 is arranged on the luffing mechanism 40. The lifting mechanism 10 is used for lifting a heavy object, and the lifting mechanism 10 includes a lifting motor 11, a wire rope 13, a hook 14, and the like. Wherein, hoist motor 11 drives wire rope 13 and coils the rope or unreel the rope to control lifting hook 14 on wire rope 13 to remove, and lifting hook 14 is connected with the lifting rope on the heavy object, thereby promotes the heavy object.

Referring to fig. 3, a process of a tower crane lifting a weight is shown. In the process of lifting the heavy object by the tower crane, the process of lifting the heavy object can be divided into several states, namely a contracting brake opening state, a rope releasing state, a loading state and a completely off-ground state according to different stress states of a lifting motor 11 for lifting the heavy object in the crane.

The state of the open band-type brake is used for indicating that the band-type brake of the crane is open, and the band-type brake is a structure arranged in the crane for preventing the lifting hook 14 from slipping off the hook. When the lifting motor 11 is started, the band-type brake is in a tightly-holding state, and when the torque of the lifting motor 11 meets the preset band-type brake opening torque, the band-type brake is opened. The magnitude of the brake opening torque can be set according to the requirement, and the embodiment does not limit the magnitude.

For example, the value of the open band brake torque may be 60% to 80% of the rated torque of the hoist motor 11. The numerical range can fully ensure the safety of the crane operation.

Specifically, as shown in fig. 4, the lifting mechanism 10 includes a roller 16 and a band-type brake, the roller 16 is connected to the lifting motor 11 and is driven by the lifting motor 11 to rotate, and the wire rope 13 is wound around the roller 16. The band-type brake is arranged outside the roller 16 and has a band-type tight state for clamping the roller 16 and an open brake state separated from the roller 16, the frequency converter 12 sends torque electric signals of the lifting motor 11 at a plurality of moments in a third time period to the signal comparison circuit 17, the signal comparison circuit 17 compares the torque electric signals at the plurality of moments with a third comparison signal, when the torque electric signals are greater than the third comparison signal, a third comparison result is obtained, and the signal transmission circuit 15 receives the third comparison result and sends an open brake signal to the band-type brake.

The third period may be the period between the start of the lifting motor 11 and the switching of the band-type brake to the open state. After the hoisting motor 11 is started, the torque sensor 18 can collect the torque of the hoisting motor 11 in real time and send the torque to the frequency converter 12, the frequency converter 12 sends the torque electric signals collected at a plurality of moments to the signal comparison circuit 17, the input of the signal comparison circuit 17 at this time is a real-time torque electric signal and a third comparison signal (i.e. a signal corresponding to a preset brake opening torque), when the torque electric signal at a certain moment is received, the signal comparison circuit 17 compares the torque electric signal with the third comparison signal, if the torque electric signal is not greater than the third comparison signal, the signal is not activated, and the torque electric signal at the next moment is waited (for example, a low level is output); if the torque electric signal is greater than the third comparison signal, a third comparison result (such as outputting a high level) is obtained. The result indicates that the band-type brake can be opened. The signal sending circuit 15 receives the third comparison result and sends an opening signal to the internal contracting brake, so that the internal contracting brake is opened, and the automatic control of the opening of the internal contracting brake can be realized.

In this embodiment, the internal contracting brake comprises an internal contracting brake clamping piece 161, an internal contracting brake transmission component and a driving component, wherein the internal contracting brake transmission component is connected between the internal contracting brake clamping piece 161 and the driving component, the driving component is electrically connected with the signal sending circuit 15, and the driving component receives an opening signal and moves along the opening direction to drive the internal contracting brake transmission component to move, so that the internal contracting brake clamping piece 161 moves to the opening state. The band-type brake with the structure can be conveniently and quickly driven through the signal sending circuit 15, so that the band-type brake can be opened in time, and the working efficiency is improved.

Preferably, in order to improve the stability of opening the band-type brake and avoid abrasion to the roller 16 caused by asynchronous movement of the band-type brake clips, the two band-type brake clips are arranged movably, the band-type brake transmission assembly comprises a driving transmission rack 162, a driven transmission rack 163 and a transmission gear 164, and the driving transmission rack 162 is arranged on one of the two band-type brake clips; the driven transmission rack 163 is arranged on the other of the two internal contracting brake clamping pieces; the transmission gear 164 is rotatably disposed between the driving rack 162 and the driven rack 163 and respectively engaged with the driving rack 162 and the driven rack 163, and the driving member is connected to the driving rack 162 and drives the driving rack 162 to move so as to drive the two internal contracting brake clamping pieces to move to the open state. Therefore, the moving synchronism of the two band-type brake clamping pieces can be fully ensured.

After the contracting brake state is opened, the torque (i.e., the output torque) of the lifting motor 11 may be different according to the load of the lifting motor 11. When hoist motor 11 is in slack rope state 11, hoist motor 11 does not bear the weight of the weight, i.e., I state shown in fig. 3. In this state, although the hook 14 is connected to the hoist rope of the weight, the hoist rope is in a slack state, and thus the hoist motor 11 is not subjected to the gravity from the weight, and the load of the hoist motor 11 is the load (i.e., the empty hook load) generated by the hook 14 and the wire rope 13. At this time, the load of the hoisting motor 11 is small, and due to PID regulation, the output torque of the hoisting motor 11 may be adjusted to be smaller than the empty hook torque for a certain period of time, and detection may be performed based on this when detecting whether the rope is in a slack state.

After passing the slack rope state, the hoisting motor 11 is in a loaded state, which is used to indicate the gravity of the part of the weight carried by the hoisting motor 11, i.e. the state II shown in fig. 3. In this state, the lifting rope of the weight is straightened, and the gravity of the weight acts on the lifting hook 14 and further acts on the lifting motor 11, so that the torque of the lifting motor 11 is increased. In this state, the weight undergoes a lift-off process.

After the loading state, the lift motor 11 is in a completely lifted-off state, i.e., state III shown in fig. 3. At this time, the lifting motor 11 bears the weight of the heavy object and lifts the heavy object.

In the above-mentioned heavy object lifting process, the gravity center position change of the heavy object lift off the ground process is the main reason for shaking, in order to avoid shaking, the heavy object lift off the ground process needs to be detected in time, and the lifting motor 11 is controlled in the process, so that the heavy object can lift off the ground more stably, thereby reducing the shaking and improving the safety.

Alternatively, in order to improve the accuracy of the detection, a rotation speed sensor may be further provided, and the rotation speed (including an actual value, a rotation direction, an acceleration state, and the like) of the hoist motor 11 is detected by the rotation speed sensor, and is determined by combining the rotation speed and the torque, so as to improve the accuracy.

The following description will be made of the determination logic, taking as an example the determination of the state of the hoist motor 11 based on the rotation speed and torque:

operation A: and determining whether the hoisting motor 11 is in a rope loosening state or not according to a torque electric signal of the hoisting motor 11 of the crane in a first period and a preset empty hook torque.

The first period of time may be any suitable period of time. The duration of the first period may be determined as desired, for example, the duration may be 40 milliseconds.

In the present embodiment, the torque of the hoisting motor 11, which can be obtained by the frequency converter 12 of the hoisting motor 11, is collected. In order to avoid the misjudgment, it may be determined in advance whether the hoisting motor 11 is in the process of hoisting the heavy object according to the actual value, the rotation direction and the acceleration state of the rotation speed of the hoisting motor 11.

For example, it is determined whether the hoist motor 11 is in a hoist state for hoisting a heavy object, based on the actual value of the rotation speed of the hoist motor 11 for the first period of time, the rotation direction.

Specifically, if the actual value of the rotation speed of the hoist motor 11 in the first period is greater than zero and the rotation direction of the hoist motor 11 in the first period is a positive direction, it is determined that the hoist motor 11 is in the hoisting state for hoisting the heavy object.

By judging the lifting state, the false triggering in the descending process can be avoided, so that the detection accuracy is improved.

If the lifting motor 11 is in the lifting state and the lifting motor 11 is in the acceleration state or the constant speed state, the torque electric signal of the lifting motor 11 in the first time period is compared with a first comparison electric signal (determined according to the empty hook torque).

By eliminating the deceleration state of the hoisting motor 11, the error judgment caused by the fact that the torque is reduced to be smaller than the idle hook torque when the hoisting motor 11 is in the deceleration state and the rotation direction of the hoisting motor 11 is the positive direction is avoided.

The condition that the torque of the lifting motor 11 is smaller than the empty hook torque can be detected in time by comparing the torque of the lifting motor 11 with the empty hook torque, if the duration time of the condition reaches the duration time of the first time period, the condition that the lifting motor 11 is in the rope loosening state can be determined according to the condition, and meanwhile, misjudgment caused by deceleration of the lifting motor 11 can be eliminated.

And operation B: when it is determined that the hoist motor 11 is in the rope-released state at the first period, it is determined whether the hoist motor 11 is in the loaded state according to the torque electric signal of the hoist motor 11 at the second period and a preset loading torque.

Since the rope slackening state and the loading state occur sequentially in the process of lifting the heavy object, under the condition that it is determined that the lifting motor 11 is in the rope slackening state, the torque electric signal of the lifting motor 11 in the second time period is acquired, and it is determined whether the lifting motor 11 is in the loading state in the second time period.

Specifically, since the reference torque according to which whether the hoist motor 11 is in the loaded state is determined to be different when the hoist motor 11 is in the acceleration state and the constant speed state, it is necessary to determine the reference torque according to the state of the rotation speed of the hoist motor 11.

For example, if it is determined that the hoist motor 11 is in the acceleration state for the second period of time based on the rotation speed of the hoist motor 11, the reference torque is the sum of the loading torque and the idling acceleration torque of the hoist motor 11.

The loading torque may be determined as required, for example, if it is required to ensure the stability of a heavy object of one ton or more during the lift-off process, the loading torque is set to a torque corresponding to the weight of one ton. The loading torque is not suitable to be too large, and needs to be ensured to be larger than the idle hook torque. The loading torque should be much less than the loading torque (i.e. the torque when the hoisting motor 11 fully bears the weight of the weight), because the rotation speed of the hoisting motor 11 is fast in the slack-rope state, so the duration of the process of the weight leaving the ground is short, and the loading state needs to be detected as soon as possible, so that the rotation speed of the hoisting motor 11 is reduced quickly and timely, and therefore setting the loading torque as small as possible facilitates the quick detection of the loading state.

Or, if it is determined that the hoist motor 11 is in the constant speed state in the second period of time according to the rotation speed of the hoist motor 11, the reference torque is equal to the loading torque.

When the lifting motor 11 is in the acceleration state, the sum of the loading torque and the idling acceleration torque required for accelerating the lifting motor 11 (i.e. the reference torque in the acceleration state) is compared with the torque of the lifting motor 11 in the second time period, and if the torque of the lifting motor 11 at each time in the second time period is determined to be greater than the reference torque based on the torque electric signal at each time in the second time period and the second comparison signal, the lifting motor 11 is determined to be in the loading state.

When the hoisting motor 11 is in the constant speed state, the loading torque is the reference torque, and the comparison process is consistent with that in the acceleration state, so the description is omitted.

And operation C: upon determining that the load state is present, the ramp deceleration time of the hoist motor 11 is reduced from the rated deceleration time to a first set value, and the rotation speed of the hoist motor 11 is reduced from the rated rotation speed to a second set value.

When it is determined that the hoisting motor 11 is in the loading state in the second time period, which indicates that the heavy object lifted by the hoisting motor 11 is in the process of lifting off the ground, in order to ensure that the heavy object is stable off the ground and reduce the shaking, the rotating speed of the hoisting motor 11 needs to be quickly adjusted to a lower rotating speed, for this reason, the rotating speed of the hoisting motor 11 is reduced by a second set value, and the ramp deceleration time of the hoisting motor 11 is reduced from the rated deceleration time to the first set value, so that the hoisting motor can reduce the rotating speed to the second set value in a shorter time.

In this embodiment, the first set value is set to a value less than or equal to 10% of the rated deceleration time of the hoisting motor 11. The first setting value in this range can ensure that the rotation speed of the hoisting motor 11 can be reduced quickly, avoiding too late adjustment. Of course, in other embodiments, other suitable ranges may be adopted, and the embodiment does not limit this.

In order to ensure the stability of the process of leaving the ground and also consider the efficiency of hoisting heavy objects, the rotating speed of the hoisting motor 11 is reduced from the rated rotating speed to a second set value. For example, the second set value ranges from 1.5% to 3% of the rated rotation speed of the hoisting motor 11, such as 30 rpm. This range of values may be sufficient to ensure stability.

Optionally, since the load change of the hoisting motor 11 tends to be stable after the heavy object is lifted off the ground, the shaking of the heavy object may also be reduced, and therefore, in order to improve the efficiency, the hoisting is avoided too slow, and the method may further include:

the process D is as follows: when it is determined that the period in which the rotation speed of the hoist motor 11 is maintained at the second set value satisfies the set period, the rotation speed of the hoist motor 11 is increased from the second set value to the third set value, and the ramp deceleration time of the hoist motor 11 is increased from the first set value to the fourth set value.

In order to realize timing, the lifting mechanism 10 further includes a timer, the timer is connected to the signal transmitting circuit 15, when the timing duration of the timer satisfies the set duration, the timer transmits a trigger signal to the signal transmitting circuit 15, and the signal transmitting circuit 15 receives the trigger signal and outputs an acceleration electric signal for increasing the driving speed of the lifting motor 11 to the frequency converter 12.

The frequency converter 12 receives the speed-increasing electric signal, so that the rotation speed of the hoist motor 11 is increased from the second set value to the third set value.

The set length of time corresponds to the time required for the weight to be lifted off the support surface, which may be equal to or greater than the time required for lifting off the support surface. Which may be determined from empirical values or from the rotational speed of the hoist motor 11, e.g. 2 seconds, 5 seconds, etc.

Taking the set time period of 2 seconds as an example, the timer starts timing from the time point when the rotation speed of the hoist motor 11 is reduced to the second set value, and when the time period determined that the rotation speed of the hoist motor 11 is maintained at the second set value reaches (the reaching can be understood as being equal to or greater than 2 seconds), the timer sends a trigger signal to the signal sending circuit 15, so that the signal sending circuit sends an acceleration electric signal to the frequency converter 12 based on the received trigger signal, thereby increasing the rotation speed of the hoist motor 11 to a third set value, so as to increase the rotation speed of the hoist motor 11, and improve the hoisting efficiency.

It is also possible to increase the ramp down time of the hoisting motor 11 to a fourth set value. The third setting value and the fourth setting value may be determined as needed, which is not limited in this embodiment. For example, the third setting may be a rated rotational speed and the fourth setting may be a rated deceleration time.

It should be noted that the above-mentioned idle hook torque, acceleration torque and loading torque can be obtained by automatic detection of the frequency converter 12, for example, before hoisting, the crane is started to perform one detection to obtain these torques. Of course, it may be determined empirically. The first set point, the second set point and the set time period may be determined empirically or through testing and debugging.

In this embodiment, the signal comparison circuit 17 and the signal transmission circuit 15 may be integrated in a controller, such as a PLC. For example, the PLC control chip includes:

the first enable pin (EN), P1 shown in fig. 6, is used to control whether the PLC is available.

A first enable output pin (ENO), P13 shown in fig. 6, is used to output a high level when the PLC is available.

A function Enable pin (Enable), P2 shown in fig. 6, is used to control whether the PLC controls the hoist motor. This pin can be connected with the switch, by navigating mate control, when needing to control the rotational speed that promotes the motor, makes the switch close.

The actual Torque PZD pin (Act Torque PZD), P3 shown in fig. 6, is used to connect with the inverter 12, receive the actual Torque transmitted by the inverter 12 in a binary manner, and convert it into a real number, such as converting the actual Torque represented in binary into a decimal value.

The reference torque pin (torque reference), P4 shown in fig. 6, is used to obtain a preset reference torque, such as the rated torque of the hoisting motor 11, for example, 965 NM.

A null hook acceleration torque pin (null vector) P5 shown in fig. 6 is used to determine the null hook acceleration torque when the hoist motor 11 is in the acceleration state. For example, the empty hook acceleration torque is 45% of the reference torque.

A blank hook torque pin (P6 shown in fig. 6) is used to determine a preset blank hook torque, for example, the blank hook torque may be 17% of the reference torque.

A loading torque pin (loading torque), P7 shown in fig. 6, is used to determine the preset loading torque, for example, the loading torque may be 21% of the reference torque. When the hoist motor 11 is in the acceleration state, the reference torque is the sum of the loading torque determined from the input of the loading torque pin and the acceleration torque determined from the input of the empty hook acceleration torque pin.

A loose rope state holding time pin (lose detect time), i.e., P8 shown in fig. 6, is used to obtain the holding time required for determining that the loose rope state is satisfied, i.e., the duration of the first period.

A load state retention time pin (loading detection time), P9 shown in fig. 6, is used to obtain the retention time required for determining that the load state is satisfied, i.e., the duration of the second period.

The holding time pin (loading time), i.e., P10 shown in fig. 6, is used to obtain a holding time period for the rotation speed of the hoist motor 11 to be at the second set value, for example, 5 seconds.

A ramp deceleration time coefficient pin (loading ramp factor), P11 shown in fig. 6, is used to obtain a coefficient for determining the first set point. For example 0.03, i.e. the first set value is 0.03 times the nominal deceleration time.

A speed coefficient pin (loading speed), P12 shown in fig. 6, is used to acquire the coefficient for determining the second set value. For example, 1.5, i.e. the second set point is 1.5% of the nominal speed.

A loading speed validation pin (loading speed condition), P14 shown in fig. 6, is used to output a high level signal when the rotation speed of the hoist motor 11 is the second set value.

A load speed 3gear condition pin (loading speed 3gear condition), P15 shown in fig. 6, is used to output a high level when the rotation speed of the hoist motor 11 is the rotation speed of the load gear control.

A load speed PZD pin (loaded speed PZD), P16 shown in fig. 6, is used to connect with the inverter 12 and output the binary rotation speed of the hoist motor 11 to the inverter 12.

A ramp down factor PZD pin (ramp down factor PZD) P17 shown in fig. 6 is used to connect to the inverter 12 and output a binary ramp down time to the inverter 12.

A PLC control pin (control by PLC), P18 shown in fig. 6, is used to interface with converter 12 to enable converter 12 to communicate with the PLC. These pins may be connected to the frequency converter 12 via the network of a profinet network to read the motor status information it collects from the frequency converter 12 and output a signal to the frequency converter 12.

For example, the PLC acquires the torque electric signal of the hoist motor 11 collected by the PLC from the frequency converter 12 for the first time period. In a first time period, each acquisition time frequency converter 12 sends a torque electric signal obtained at the current time to the PLC, the signal comparison circuit compares the torque electric signal at the current time with a first comparison signal, if the duration of the torque electric signal is less than 40 milliseconds, which is set, the 40 milliseconds can be regarded as the first time period, and a first comparison result is sent to the signal sending circuit, so that it can be determined that the hoisting motor 11 is in a rope loosening state.

Upon determining that it is in the slack condition, the PLC obtains from the frequency converter 12 the torque electrical signal of the hoist motor 11 it collected for the second period of time. In a second time period, each acquisition time frequency converter 12 sends a torque electric signal obtained at the current time to the PLC, the signal comparison circuit compares the torque electric signal at the current time with a second comparison signal (the second comparison signal is determined according to the reference torque), and if the torque electric signal is greater than the second comparison signal and the duration time meets the set 20 milliseconds, the 20 milliseconds can be the second time period, and a second comparison result is sent to the signal sending circuit, so that the lifting motor 11 is determined to be in a loading state.

The signal transmission circuit transmits a deceleration electric signal to the inverter 12 to reduce the rotation speed of the hoist motor 11.

In addition, the signal sending circuit can also send speed and speed adjusting signals to the frequency converter 12 to reduce the slope deceleration time, so that the slope deceleration time and the rotating speed of the lifting motor 11 are automatically reduced at the moment when the heavy object leaves the ground, and the purpose of stably leaving the ground is achieved. After the heavy object is lifted off the ground, the rotation speed and the ramp deceleration time of the hoisting motor 11 are restored to the initial ramp deceleration time (i.e., the rated deceleration time) and the initial speed.

Detect and control through independent circuit, can realize the steady promotion of heavy object automatically, avoid manual operation error's problem, improve hoist mechanism 10 efficiency for the heavy object can be faster, more stable promotion. And the use of an independent controller can reduce the resource occupancy rate of the frequency converter 12, simplify the debugging process, and avoid debugging in the frequency converter 12.

According to the utility model discloses a another aspect provides a tower crane, and it includes body of the tower 20, rotation mechanism 30, davit and hoist mechanism 10, and rotation mechanism 30 sets up on body of the tower 20, and the davit sets up on rotation mechanism 30, and hoist mechanism 10 sets up on the davit, and hoist mechanism 10 is foretell hoist mechanism 10.

The frequency converter 12 on the lifting mechanism 10 can be debugged in advance, so that an empty hook torque, a loading torque, an accelerating torque and the like meeting the use scene are obtained, the lifting motor 11 can be controlled in the process of lifting the heavy object, and the process of lifting the heavy object off the ground is more stable and less in shaking. For example, when the hoisting is not performed stably by the control system, the speed and torque of the hoisting motor 11 greatly fluctuate due to the fluctuation of the heavy object, and the fluctuation of the torque reaches 90NM, so that the boom of the luffing mechanism 40 is seriously fluctuated, and the hoisting process is very dangerous. When the control system is used for carrying out stable lifting, torque fluctuation is very small and is only about 10NM in the lifting process no matter in the lift-off process or after the lift-off process is completed, and the rotating speed mechanism of the lifting motor 11 does not fluctuate, so that the effect of stably lifting the ground is achieved.

According to the embodiment of the application, the lifting mechanism of the tower crane has the following beneficial effects:

the lifting mechanism can automatically detect the lift-off process of the heavy object, automatically adjust the rotating speed and the slope deceleration time of the lifting motor 11, automatically and stably lift the heavy object in the lift-off process, avoid manual operation errors, improve the lifting efficiency and enable the heavy object to be lifted stably and quickly. In addition, the control is carried out through an independent circuit, the resource of the frequency converter 12 is not required to be occupied, the debugging process can be simplified, and additional debugging in the frequency converter 12 is not required.

It should be understood that although the present description has been described in terms of various embodiments, not every embodiment includes only a single embodiment, and such description is for clarity purposes only, and those skilled in the art will recognize that the embodiments described herein may be combined as suitable to form other embodiments, as will be appreciated by those skilled in the art.

The above description is only an exemplary embodiment of the present disclosure, and is not intended to limit the scope of the present disclosure. Any person skilled in the art should be able to make equivalent changes, modifications and combinations without departing from the concept and principle of the embodiments of the present application.

Claims (9)

1. The lifting mechanism of the tower crane is characterized by comprising a lifting motor (11), a frequency converter (12), a steel wire rope (13), a lifting hook (14), a signal comparison circuit (17) and a signal sending circuit (15), wherein the lifting motor (11) is connected with the steel wire rope (13) and drives the steel wire rope (13) to wind or unwind, a torque sensor (18) is arranged on the lifting motor (11), and the lifting hook (14) is arranged on the steel wire rope (13) and moves upwards or downwards along with the winding or unwinding of the steel wire rope (13);

the frequency converter (12) is electrically connected with the lifting motor (11) to drive the lifting motor (11), the frequency converter (12) is electrically connected with the torque sensor (18), and the frequency converter (12) receives a torque electric signal of the lifting motor (11) from the torque sensor (18);

the frequency converter (12) sends torque electric signals of the lifting motor (11) in a first time period and a second time period to the signal comparison circuit (17), the signal comparison circuit (17) compares that the torque electric signals in the first time period are smaller than a first comparison signal to obtain a first comparison result, the signal comparison circuit (17) compares that the torque electric signals in the second time period are larger than a second comparison signal to obtain a second comparison result, and the signal sending circuit (15) receives the first comparison result and the second comparison result and outputs a deceleration electric signal for reducing the driving speed of the lifting motor (11) to the frequency converter (12).

2. The lifting mechanism of tower crane according to claim 1, wherein the lifting mechanism comprises a roller (16) and a band-type brake, the roller (16) is connected with the lifting motor (11) and driven by the lifting motor (11) to rotate, the band-type brake is arranged outside the roller (16) and has a tightly-holding state for clamping the roller (16) and an open-brake state separated from the roller (16), the frequency converter (12) sends torque electric signals of the lifting motor (11) at a plurality of moments in a third time period to the signal comparison circuit (17), the signal comparison circuit (17) compares the torque electric signals at the plurality of moments with a third comparison signal respectively, and when the torque electric signals are greater than the third comparison signal, a third comparison result is obtained, the signal sending circuit (15) receives the third comparison result, and sending a brake opening signal to the band-type brake.

3. The hoisting mechanism of tower crane according to claim 2, wherein the band-type brake comprises a band-type brake clamping piece (161), a band-type brake transmission assembly and a driving piece, the band-type brake transmission assembly is connected between the band-type brake clamping piece (161) and the driving piece, the driving piece is electrically connected with the signal sending circuit (15), and the driving piece receives the brake opening signal and moves along the brake opening direction to drive the band-type brake transmission assembly to move, so that the band-type brake clamping piece (161) moves to the brake opening state.

4. The lifting mechanism of a tower crane according to claim 3, wherein the brake clips (161) are two and relatively movably disposed, and the brake transmission assembly comprises:

a driving transmission rack (162), wherein the driving transmission rack (162) is arranged on one of the two band-type brake clamping pieces (161);

a driven transmission rack (163), the driven transmission rack (163) being provided on the other of the two band-type brake clips (161);

drive gear (164), drive gear (164) rotationally set up drive transmission rack (162) with between driven transmission rack (163), and respectively with drive transmission rack (162) with driven transmission rack (163) meshing, the driving piece with drive transmission rack (162) are connected, and the drive transmission rack (162) remove, in order to drive two band-type brake clamping piece (161) remove to the state of opening the floodgate.

5. The lifting mechanism of a tower crane according to claim 1, further comprising a timer, wherein the timer is connected to the signal transmission circuit (15), and when the timing duration of the timer satisfies a set duration, the timer transmits a trigger signal to the signal transmission circuit (15), and the signal transmission circuit (15) receives the trigger signal and outputs an acceleration electric signal for increasing the driving speed of the lifting motor (11) to the frequency converter (12).

6. The hoisting mechanism of a tower crane according to claim 1, characterized in that it further comprises a switch arranged in the cab of the crane, said switch being connected between the frequency converter (12) and the signal comparison circuit (17), said switch having a closed position in which the frequency converter (12) and the signal comparison circuit (17) are connected, and an open position in which the frequency converter (12) and the signal comparison circuit (17) are disconnected.

7. The hoisting mechanism of tower crane according to claim 6, further comprising a switch box, wherein the switch comprises a first portion and a second portion, the first portion is disposed in the switch box, the second portion protrudes from the top surface of the switch box, a circuit board is disposed in the switch box, the signal comparison circuit (17) and the signal transmission circuit (15) are disposed on the circuit board, and a potting material layer covering the circuit board, the signal comparison circuit (17) and the signal transmission circuit (15) is disposed in the switch box.

8. The hoisting mechanism of a tower crane according to any one of claims 1-7, wherein the signal comparison circuit (17) comprises a comparator and a comparison signal source, the comparator comprising a forward input, a backward input and an output;

the positive input end is connected with the frequency converter (12) and receives the torque electric signal in the first time period and the torque electric signal in the second time period which are sent by the frequency converter (12);

the reverse input end is connected with the comparison signal source and receives a first comparison signal sent by the comparison signal source in the first time interval and a second comparison signal sent by the comparison signal source in the second time interval;

the output end is connected with the signal transmitting circuit (15).

9. A tower crane, characterized by comprising a tower body (20), a slewing mechanism (30), a boom and a lifting mechanism (10), said slewing mechanism (30) being arranged on said tower body (20), said boom being arranged on said slewing mechanism (30), said lifting mechanism (10) being arranged on said boom, said lifting mechanism (10) being a lifting mechanism according to any one of claims 1-8.

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