Slow stopping apparatus for working machine

Provided is a slow stopping apparatus for a working machine which can shorten a stopping time while suppressing a cargo swing. The slow stopping apparatus includes a first slow stopper 21 which calculates a cargo swing cycle T and takes a time T1 in a half of the cargo swing cycle T to stop an actuator 10 when a stop signal is input, a second slow stopper 22 which takes a shorter time T2 than the time T1 in the half of the cargo swing cycle T to stop the actuator 10, a cargo swing predictor 23 which predicts whether a load amplitude A would exceed an allowable value, and a switcher 24 which switches the first slow stopper 21 and the second slow stopper 22 in accordance with prediction of the cargo swing predictor 23. It is possible to suppress a cargo swing in stop of a motion of the working machine, thereby shortening a time required for stopping the motion of the working machine.

TECHNICAL FIELD

The present invention relates to a slow stopping apparatus for a working machine. More specifically, the present invention relates to a slow stopping apparatus for a working machine which serves to suppress a cargo swing when stopping a motion of a working machine having a boom such as an aerial work platform or a crane.

BACKGROUND ART

As a slow stopping apparatus for a working machine, there is known an apparatus for braking a motion speed of a boom at a constant acceleration to stop the working machine when a motion of the boom is stopped suddenly by an operating lever (for example, Patent Document 1). By reducing a speed at a constant acceleration, it is possible to slowly stop the boom, thereby suppressing a cargo swing.

However, the conventional slow stopping apparatus does not take a flexure of the boom into consideration. For this reason, there is a problem in that the boom is flexed in the stop of the motion of the boom and a cargo swing is caused by the flexure in a specific posture of the boom, particularly, a state in which the boom is extended.

On the other hand, Patent Document 2 discloses the technique for calculating a cargo swing cycle time in consideration of the flexure of the boom and braking a motion speed of the boom in a cargo swing cycle time at a constant acceleration, thereby carrying out stop. By the technique, it is possible to suppress a cargo swing including the flexure of the boom when stopping the motion of the boom.

It is known that an amount of the flexure of the boom is proportional to an acceleration and a mass (a weight) of a cargo supported by the boom. In more detail, the flexure of the boom can approximate to that of a cantilever and an amount δ of the flexure of the cantilever is expressed in the following Equation 1.

δ=Fl33⁢⁢EI[Equation⁢⁢1]
wherein F represents a force to be applied in a perpendicular direction to a free end of a cantilever, I represents a length of the cantilever, E represents a Young's modulus of the cantilever, and I represents a secondary cross-sectional moment of the cantilever. In other words, the amount δ of the flexure is proportional to the force F to be applied to the cantilever. In the case of a flexure generated when the motion of the boom is stopped suddenly, the force F is an inertial force (F=ma) of the cargo supported on the boom. For this reason, the amount of the flexure of the boom is proportional to an acceleration a and a mass m of the cargo supported on the boom.

In the case in which the motion of the boom is stopped suddenly, the acceleration of the boom is increased with a rise in a motion speed just before a sudden stop, resulting in an increase in the acceleration of the cargo on the assumption that the motion speed is 0 within a constant time regardless of the motion speed of the boom. For this reason, the amount of the flexure of the boom is proportional to the motion speed just before a sudden stop. In other words, in the case in which the motion speed of the boom is high, the sudden stop causes the flexure of the boom to be increased, resulting in an increase in a load amplitude. On the other hand, in the case in which the motion speed of the boom is low, the sudden stop causes the amount of the flexure of the boom to be reduced, resulting in a decrease in the load amplitude. On the other hand, the cargo swing cycle time does not depend on the motion speed of the boom.

Referring to the technique described in the Patent Document 2, the cargo swing cycle time is taken to carry out stop regardless of the motion speed of the boom. For this reason, there is a problem in that a time required for the stop is increased also in the case in which the motion speed of the boom is low and the cargo swing does not matter.

PRIOR ART DOCUMENT

Patent Document

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

In consideration of the circumstances, it is an object of the present invention to provide a slow stopping apparatus for a working machine which can shorten a time required for stop while suppressing a cargo swing.

Means for Solving the Problem

A slow stopping apparatus for a working machine according to a first invention is provided in the working machine having a boom which supports a cargo and includes an actuator which operates the working machine, a control unit which controls a driving motion of the actuator and an operating unit which gives an instruction to operate the working machine to the control unit, and the control unit includes a first slow stopper which calculates a cargo swing cycle of the cargo and takes a time in a half of the cargo swing cycle to brake and stop the actuator when a stop signal for giving an instruction to stop a motion of the working machine is input from the operating unit, a second slow stopper which takes a shorter time than the time in the half of the cargo swing cycle to brake and stop the actuator when the stop signal is input from the operating unit, a cargo swing predictor which predicts whether a load amplitude of the cargo would exceed an allowable value, and a switcher which stops the actuator by the first slow stopper when the cargo swing predictor predicts that the load amplitude of the cargo would exceed the allowable value and stops the actuator by the second slow stopper when the cargo swing predictor predicts that the load amplitude of the cargo would not exceed the allowable value.

In the first invention, the slow stopping apparatus for a working machine according to a second invention features that the first slow stopper calculates a cargo swing cycle of the cargo based on a posture of the boom and a weight of the cargo and takes a time in a half of the cargo swing cycle to brake and stop the actuator when a stop signal for giving an instruction to stop a motion of the boom is input from the operating unit.

In the first invention, the slow stopping apparatus for a working machine according to a third invention features that the working machine includes a hook suspended from the boom for hanging the cargo thereon, and the first slow stopper calculates a cargo swing cycle of the cargo based on a posture of the boom, a suspension distance of the hook and a weight of the cargo and takes a time in a half of the cargo swing cycle to brake and stop the actuator when a stop signal for giving an instruction to stop a motion of the boom is input from the operating unit.

In the first invention, the slow stopping apparatus for a working machine according to a fourth invention features that the working machine includes a hook suspended from the boom for hanging the cargo thereon, and the first slow stopper calculates a cargo swing cycle of the cargo based on a posture of the boom and a weight of the cargo and takes a time in a half of the cargo swing cycle to brake and stop the actuator when a stop signal for giving an instruction to stop the motion of the hook is input from the operating unit.

In the first or second invention, the slow stopping apparatus for a working machine according to a fifth invention features that the cargo swing predictor calculates a load amplitude of the cargo based on a posture of the boom, a motion speed of the boom and a weight of the cargo, and decides that the load amplitude of the cargo would exceed an allowable value when the load amplitude exceeds a threshold and decides that the load amplitude of the cargo would not exceed the allowable value when the load amplitude does not exceed the threshold.

In the first or third invention, the slow stopping apparatus for a working machine according to a sixth invention features that the working machine includes a hook suspended from the boom for hanging the cargo thereon, and the cargo swing predictor calculates a load amplitude of the cargo based on a posture of the boom, a suspension distance of the hook, a motion speed of the boom and a weight of the cargo, and decides that the load amplitude of the cargo would exceed an allowable value when the load amplitude exceeds a threshold and decides that the load amplitude of the cargo would not exceed the allowable value when the load amplitude does not exceed the threshold.

In the first or fourth invention, the slow stopping apparatus for a working machine according to a seventh invention features that the working machine includes a hook suspended from the boom for hanging the cargo thereon, and the cargo swing predictor calculates a load amplitude of the cargo based on a posture of the boom, a motion speed of the hook and a weight of the cargo, and decides that the load amplitude of the cargo would exceed an allowable value when the load amplitude exceeds a threshold and decides that the load amplitude of the cargo would not exceed the allowable value when the load amplitude does not exceed the threshold.

In the first, second, third or fourth invention, the slow stopping apparatus for a working machine according to an eighth invention features that there is provided a speed detector for detecting a motion speed of the working machine, and the cargo swing predictor decides that the load amplitude of the cargo would exceed the allowable value when a result of detection of the speed detector exceeds a threshold, and decides that the load amplitude of the cargo would not exceed the allowable value when the result of the detection of the speed detector does not exceed the threshold.

In the first, second, third or fourth invention, the slow stopping apparatus for a working machine according to a ninth invention features that there is provided a posture detector for detecting a posture of the boom, and the cargo swing predictor decides that the load amplitude of the cargo would exceed the allowable value when a result of detection of the posture detector exceeds a threshold, and decides that the load amplitude of the cargo would not exceed the allowable value when the result of the detection of the posture detector does not exceed the threshold.

In the first, second, third or fourth invention, the slow stopping apparatus for a working machine according to a tenth invention features that there is provided a weight detector which detects a weight of the cargo, and the cargo swing predictor decides that the load amplitude of the cargo would exceed the allowable value when a result of detection of the weight detector exceeds a threshold, and decides that the load amplitude of the cargo would not exceed the allowable value when the result of the detection of the weight detector does not exceed the threshold.

Effect of the Invention

According to the first invention, in the case in which it is predicted that the load amplitude would exceed the allowable value, the actuator is stopped by the first slow stopper. Therefore, it is possible to suppress the cargo swing when stopping the motion of the working machine. In the case in which it is predicted that the load amplitude would not exceed the allowable value, the actuator is stopped by the second slow stopper. Therefore, it is possible to shorten a time required for stopping the motion of the working machine. In addition, it is possible to control the load amplitude within an allowable range. Therefore, it is possible to shorten a stopping time while suppressing the cargo swing.

According to the second invention, in the case in which the motion of the boom is stopped, the cargo swing cycle is calculated based on the posture of the boom and the weight of the cargo. Therefore, it is possible to accurately predict the cargo swing cycle, thereby suppressing the cargo swing sufficiently.

According to the third invention, in the case in which the motion of the boom having the hook is stopped, the cargo swing cycle is calculated based on the posture of the boom, the suspension distance of the hook and the weight of the cargo. Therefore, it is possible to accurately predict the cargo swing cycle, thereby suppressing the cargo swing sufficiently.

According to the fourth invention, in the case in which the motion of the hook is stopped, the cargo swing cycle is calculated based on the posture of the boom and the weight of the cargo. Therefore, it is possible to accurately predict the cargo swing cycle, thereby suppressing the cargo swing sufficiently.

According to the fifth invention, in the case in which the motion of the boom is stopped, the load amplitude is calculated based on the posture of the boom, the motion speed of the boom and the weight of the cargo and it is predicted whether the allowable value would be exceeded based on the load amplitude. Therefore, it is possible to accurately predict the cargo swing, thereby switching the first slow stopper and the second slow stopper properly.

According to the sixth invention, in the case in which the motion of the boom having the hook is stopped, the load amplitude is calculated based on the posture of the boom, the suspension distance of the hook, the motion speed of the boom and the weight of the cargo and it is predicted whether the allowable value would be exceeded based on the load amplitude. Therefore, it is possible to accurately predict the cargo swing, thereby switching the first slow stopper and the second slow stopper properly.

According to the seventh invention, in the case in which the motion of the hook is stopped, the load amplitude is calculated based on the posture of the boom, the motion speed of the hook and the weight of the cargo and it is predicted whether the allowable value would be exceeded based on the load amplitude. Therefore, it is possible to accurately predict the cargo swing, thereby switching the first slow stopper and the second slow stopper properly.

According to the eighth invention, the result of the detection of the speed detector is compared with the threshold. Consequently, it is predicted whether the load amplitude would exceed the allowable value. Therefore, the first slow stopper and the second slow stopper are switched based on the motion speed of the boom or the hook. Consequently, a worker can predict which slow stopper stops the boom or hook. Thus, operability can be improved.

According to the ninth invention, the result of the detection of the posture detector is compared with the threshold. Consequently, it is predicted whether the load amplitude would exceed the allowable value. Therefore, the first slow stopper and the second slow stopper are switched based on the posture of the boom. Consequently, the worker can predict which slow stopper stops the boom or hook. Thus, the operability can be improved.

According to the tenth invention, the result of the detection of the weight detector is compared with the threshold. Consequently, it is predicted whether the load amplitude would exceed the allowable value. Therefore, the first slow stopper and the second slow stopper are switched based on the weight of the cargo. Consequently, the worker can predict which slow stopper stops the boom or hook. Thus, the operability can be improved.

MODE FOR CARRYING OUT THE INVENTION

Next, embodiments according to the present invention will be described with reference to the drawings.

A slow stopping apparatus for a working machine according to the present invention is provided in all working machines having a boom which supports a cargo, for example, an aerial work platform, a crane or the like, and is used for suppressing a cargo swing in stop of a motion of the working machine. Description will be given by taking, as an example, the case of an aerial work platform and a mobile crane.

First Embodiment

A slow stopping apparatus1according to a first embodiment of the present invention is provided in an aerial work platform. First of all, a basic structure of an aerial work platform100will be described with reference toFIG. 3.

InFIG. 3, the reference numeral110denotes a vehicle, and a slewing table120is mounted in a rear part of a cargo bed of a vehicle110. A turning motion of the slewing table120is carried out by a turning motor. A multistage boom130is attached to the slewing table120so as to be freely derricked. An expanding/contracting motion of the boom130is carried out by an expanding/contracting cylinder and a derricking motion is carried out by a derricking cylinder. A tip of the boom130is provided with a basket-shaped bucket140on which a worker can get. The bucket140is always maintained horizontally regardless of a change in a derricking angle of the boom130and can be turned in a horizontal plane.

When the boom130is turned in the aerial work platform100and the turning motion is stopped suddenly, the boom130is flexed by an inertial force of the bucket140so that the bucket140is swung in a horizontal direction by the flexure. When the boom130is derricked and the derricking motion is stopped suddenly, moreover, the boom130is flexed by the inertial force of the bucket140so that the bucket140is swung in a perpendicular direction by the flexure.

The slow stopping apparatus1according to the present embodiment is used for suppressing the swing of the bucket140when stopping the turning or derricking motion of the boom130in the aerial work platform100.

In the aerial work platform100, the “cargo” described in claims means the bucket140provided on the tip of the boom130and a loaded object such as a worker that is loaded on the bucket140(which will be hereinafter referred to as the “bucket140”). The “weight of a cargo” means a weight of the bucket140including the loaded object (which will be hereinafter referred to as the “weight of the bucket140”), and the “cargo swing” means a swing of the bucket140.

Next, the structure of the slow stopping apparatus1will be described.

As shown inFIG. 1, the slow stopping apparatus1includes an actuator10which operates the aerial work platform100, a control unit20which controls a driving motion of the actuator10, an operating unit30which gives an instruction to operate the aerial work platform100to the control unit20, and a posture detector40which detects a posture of the boom130.

In the present embodiment, the actuator10is a turning motor for turning the boom130or a derricking cylinder for derricking the boom130.

The control unit20is an on-vehicle computer configured from a CPU, a memory and the like and is a unit for controlling the driving motion of the actuator10in accordance with the instruction given by the operating unit30. In general, the actuator10of the aerial work platform100is a hydraulic actuator and a hydraulic circuit for supplying hydraulic oil to the hydraulic actuator is connected to the hydraulic actuator. The control unit20switches a valve forming the hydraulic circuit or the like to control a direction or a flow rate of the hydraulic oil to be supplied to the actuator10, thereby controlling a driving direction or a driving speed of the actuator10.

The operating unit30includes an operating lever, an operating pedal, a switch and the like which are provided in the vehicle110and the bucket140in the aerial work platform100. The control unit20controls the driving speed of the actuator10in accordance with an operating amount (an amount of inclination of the operating lever) of the operating unit30. More specifically, when the operating amount of the operating unit30is increased, the actuator10is controlled to have the driving speed increased so that the turning speed or derricking speed of the boom130is increased. When the operating amount of the operating unit30is reduced, moreover, the actuator10is controlled to have the driving speed reduced so that the turning speed of derricking speed of the boom130is reduced. In the case in which the operating unit30is not operated (the operating amount is 0), moreover, a stop signal for giving an instruction to stop the motion of the boom130is input from the operating unit30to the control unit20.

The posture detector40is configured from various sensors for measuring a turning angle, a derricking angle and an expansion/contraction length, and the like. A result of the detection of the posture detector40is input to the control unit20.

The control unit20includes first slow stopper21, second slow stopper22, cargo swing predictor23, and switcher24and is configured to stop the actuator10which is being driven in their cooperation. The first slow stopper21, the second slow stopper22, the cargo swing predictor23and the switcher24are implemented by execution of a program through the control unit20.

The control unit20has a function for driving the actuator10in accordance with the operating amount of the operating unit30in addition to the function for stopping the actuator10, and a unit for implementing the function is omitted inFIG. 1.

Signals are input from the operating unit30and the posture detector40to the first slow stopper21. The first slow stopper21stops the actuator10by the following slow stopping method when a stop signal for giving an instruction to stop the motion of the boom130is input from the operating unit30to the first slow stopper21.

First of all, the first slow stopper21calculates a cargo swing cycle T of the bucket140based on the result of the detection of the posture detector40and the weight of the bucket140which is prestored when inputting the stop signal from the operating unit30. Herein, the cargo swing cycle T represents a cycle of a natural vibration of the bucket140which is generated when the motion of the boom130is stopped suddenly. It is known that the cargo swing cycle T of the bucket140is uniquely determined by the posture of the boom130(the derricking angle and the expansion/contraction length) and the weight of the bucket140.

The first slow stopper20has such a structure as to prestore information such as a dead weight, a structure or a rigidity about the boom130and to dynamically calculate the cargo swing cycle T based on the information, the result of the detection of the posture detector40(the posture of the boom130) and the weight of the bucket140.

Moreover, it is also possible to employ a structure in which the cargo swing cycle T for each posture of the boom130is previously obtained by a test and is stored in the first slow stopper21, and the first slow stopper21calls the cargo swing cycle T corresponding to the result of the detection of the posture detector40from the cargo swing cycle T for each posture of the boom130which is stored.

It is also possible to employ a structure in which a weight detector for detecting the weight of the bucket140is provided and the cargo swing cycle T is calculated based on the results of the detection of the posture detector40and the weight detector. In the aerial work platform100, however, the weight of the bucket140itself is constant and the weight of the loaded object such as a worker does not fluctuate greatly. For this reason, the fluctuation in the weight of the bucket140is small. Also with a structure in which the weight of the bucket140has a fixed value as in the present embodiment, therefore, the calculated cargo swing cycle T has a small error.

Next, the first slow stopper21outputs a control signal in order to take a time T1(=T/2) in a half of the calculated cargo swing cycle T, thereby braking and stopping the actuator10. In more detail, as shown inFIG. 2, it is assumed that the motion speed of the boom130is represented by v in the case in which the operating amount of the operating unit30is represented by p. In the case in which the operating amount of the operating unit30is changed from p to 0 (a non-operation state) at a time t (FIG. 2(a)), the first slow stopper21brakes the actuator10in such a manner that the motion speed of the boom130is 0 when the time T1passes since the time t (FIG. 2(b)).

Thus, it is known that the cargo swing in the stop of the motion of the boom130can be suppressed by taking the time T1in the half of the cargo swing cycle T to brake and stop the actuator10. Although an acceleration in speed reduction is made constant inFIG. 2(b), it does not need to be constant.

The second slow stopper22inputs signals from the operating unit30and the posture detector40. The second slow stopper22stops the actuator10by the following slow stopping methods when inputting the stop signal from the operating unit30.

The second slow stopper22outputs a control signal in order to take a prestored time T2, thereby braking and stopping the actuator10when inputting the stop signal from the operating unit30. In more detail, as shown inFIG. 2, in the case in which the operating amount of the operating unit30is changed from p to 0 (the non-operation state) at the time t (FIG. 2(a)), the second slow stopper21brakes the actuator10in such a manner that the motion speed of the boom130is 0 when the time T2passes since the time t (FIG. 2(c)).

Herein, the time T2is set to be shorter than the time T1in the half of the cargo swing cycle T. For this reason, when the actuator10is stopped by the second slow stopper22, the cargo swing occurs corresponding to a shorter portion than the time T1. A value of the time T2is predetermined by a test. More specifically, times required for the stop are obtained to cause the load amplitude to fall within a predetermined range every posture of the boom130, and are set to be the times T2. Herein, the “load amplitude” means an amplitude of the cargo swing.

The second slow stopper22calls the time T2corresponding to the result of the detection of the posture detector40from the times T2for postures of the boom130which are stored, and outputs a control signal in order to take the time T2, thereby stopping the actuator10.

The time T2may be determined as a constant value regardless of the posture of the boom130. In this case, the result of the detection of the posture detector40is not input to the second slow stopper22. The second slow stopper22outputs a control signal in order to take the prestored time T2, thereby stopping the actuator10regardless of the posture of the boom130.

The cargo swing predictor23inputs signals from the operating unit30and the posture detector40. The cargo swing predictor23predicts whether the load amplitude in the sudden stop of the motion of the boom130would exceed an allowable value based on the operating amount of the operating unit30, the result of the detection of the posture detector40and the weight of the bucket140which is prestored. In the present embodiment, the cargo swing predictor23carries out prediction by the following method.

First of all, the cargo swing predictor23calculates a load amplitude A of the bucket140based on the operating amount of the operating unit30, the result of the detection of the posture detector40and the weight of the bucket140. It is known that the load amplitude A of the packet140is determined by the posture of the boom130(the derricking angle and the expansion/contraction length), the motion speed of the boom130and the weight of the bucket140(including the weight of the loaded object).

In the present embodiment, the motion speed of the boom130is acquired from the operating amount of the operating unit30. More specifically, an operating amount p just before the operating amount of the operating unit30is 0 is set to be the motion speed of the boom130as shown inFIG. 2(a). In other words, the operating unit30also plays a role as the speed detector for detecting the motion speed of the boom130in the present embodiment.

The motion speed of the boom130may be calculated based on a time change in the result of the detection of the posture detector40(the posture of the boom130). Moreover, a speed detector for detecting the motion speed of the boom130may be provided in addition to the operating unit30. Thus, the “speed detector” described in the claims has such a concept that it is not restricted to a unit for directly detecting the motion speed of the boom130but includes a unit for indirectly detecting the motion speed of the boom130, for example, the operating unit30or the posture detector40.

The cargo swing predictor23has a structure in which information such as a structure or a rigidity about the boom130is prestored and the load amplitude A is dynamically calculated based on the information, the operating amount of the operating unit30(the motion speed of the boom130), the result of the detection of the posture detector40(the posture of the boom130) and the weight of the bucket140.

Moreover, it is also possible to employ a structure in which the load amplitudes A for postures and motion speeds of the boom130are previously obtained by a test and are stored in the cargo swing predictor23, and the cargo swing predictor23calls the load amplitude A corresponding to the operating amount of the operating unit30and the result of the detection of the posture detector40from the load amplitudes A for postures and motion speeds of the boom130which are stored.

Next, the cargo swing predictor23decides that the load amplitude A would exceed an allowable value when the calculated load amplitude A exceeds a prestored threshold, and decides that the load amplitude A would not exceed the allowable value when the calculated load amplitude A does not exceed the threshold.

Herein, the threshold is predetermined as an allowable maximum value of the load amplitude A. For example, the threshold is determined as a maximum value of the load amplitude A by which a worker getting on the bucket140does not feel uncomfortable.

The switcher24inputs control signals output from the first slow stopper21and the second slow stopper22respectively, and selects any of the control signals and outputs the control signal to the actuator10. The switcher24is connected to the cargo swing predictor23, and outputs the control signal of the first slow stopper21to the actuator10to stop the actuator10by the first slow stopper21when the cargo swing predictor23predicts that the load amplitude A would exceed the allowable value. When the cargo swing predictor23predicts that the load amplitude A would not exceed the allowable value, moreover, the switcher24outputs the control signal of the second slow stopper22to the actuator10, thereby stopping the actuator10by the second slow stopper22.

Next, the motion of the slow stopping apparatus1will be described.

As shown inFIG. 2, when the worker operates the operating unit30to change the operating amount of the operating unit30from p to 0 (the non-operation state) at the time t (FIG. 2(a)), the first slow stopper21outputs the control signal to take the time T1in the half of the cargo swing cycle T, thereby stopping the actuator10(FIG. 2(b)). On the other hand, the second slow stopper22outputs the control signal to take the shorter time T2than the time T1, thereby stopping the actuator10(FIG. 2(c)). Moreover, the cargo swing predictor23predicts whether the load amplitude A would exceed the allowable value based on the operating amount p of the operating unit30just before a sudden stop, the result of the detection of the posture detector40and the weight of the bucket140.

In the case in which the expansion/contraction length of the boom130is great or the case in which the motion speed of the boom130is high, the cargo swing predictor23predicts that the load amplitude A would exceed the allowable value. In this case, the switcher24outputs the control signal of the first slow stopper21to the actuator10to stop the actuator10by the first slow stopper21. For this reason, it is possible to suppress the cargo swing in the stop of the motion of the boom130.

On the other hand, in the case in which the expansion/contraction length of the boom130is small or the case in which the motion speed of the boom130is low, the cargo swing predictor23predicts that the load amplitude A would not exceed the allowable value. In this case, the switcher24outputs the control signal of the second slow stopper22to the actuator10to stop the actuator10by the second slow stopper22. For this reason, it is possible to shorten a time required for stopping the motion of the boom130. In addition, it is predicted that the load amplitude A would not exceed the allowable value. Even if the actuator10is stopped by the second slow stopper22, therefore, it is possible to control the load amplitude A to fall within an allowable range.

As described above, according to the slow stopping apparatus1, it is possible to shorten the stopping time while suppressing the cargo swing.

Moreover, the cargo swing predictor23according to the present embodiment predicts the load amplitude A based on the operating amount of the operating unit30(the motion speed of the boom130), the result of the detection of the posture detector40(the posture of the boom130) and the weight of the bucket140and predicts whether the allowable value would be exceeded based on the load amplitude A in the case in which the motion of the boom130is stopped. Consequently, it is possible to accurately predict the cargo swing. Therefore, it is possible to properly switch the first slow stopper21and the second slow stopper22, and to shorten the stopping time while suppressing the cargo swing reliably.

Second Embodiment

A slow stopping apparatus2according to a second embodiment of the present invention is provided in a mobile crane. First of all, a basic structure of a mobile crane200will be described with reference toFIG. 5.

InFIG. 5, the reference numeral210is a running vehicle body and a slewing table220is mounted on an upper surface of the running vehicle body210. A turning motion of the slewing table220is carried out by a turning motor. A multistage boom230is attached to the slewing table220so as to be freely derricked. An expanding/contracting motion of the boom230is carried out by an expanding/contracting cylinder and a derricking motion is carried out by a derricking cylinder. A wire rope241including a hook240is suspended from a tip of the boom230and is led to a base of the boom230and is wound upon a winch. When the winch is rotated to wind the wire rope241, thereby carrying out feeding, the hook240can be moved upward/downward. A suspended cargo250can be hung on the hook240. By combining the turning, derricking and expanding/contracting motions of the boom230and the upward/downward movement of the hook240, it is possible to move the suspended cargo250upward and downward in a three-dimensional space.

When the boom230is turned in the mobile crane200and the turning motion is stopped suddenly, the suspended cargo250is swung like a pendulum in a horizontal direction by an inertial force of the suspended cargo250, and furthermore, the boom230is flexed by the inertial force of the suspended cargo250so that the suspended cargo250is swung in the horizontal direction by the flexure. Moreover, when the boom230is derricked and the derricking motion is stopped suddenly, the boom230is flexed by the inertial force of the suspended cargo250and the suspended cargo250is swung in a perpendicular direction by the flexure, and furthermore, the suspended cargo250is swung like a pendulum in the horizontal direction by a horizontal direction component of the inertial force of the suspended cargo250. In addition, when the boom230is expanded/contracted and the expanding/contracting motion is stopped suddenly, the suspended cargo250is swung like the pendulum in the horizontal direction by the horizontal direction component of the inertial force of the suspended cargo250.

The slow stopping apparatus2according to the present embodiment is used for suppressing the swing of the suspended cargo250when stopping the turning, derricking or expanding/contracting motion of the boom230in the mobile crane200.

In the mobile crane200, the “cargo” described in the claims means the suspended cargo250which is suspended from the hook240, the “weight of a cargo” means a sum of the weight of the hook240and that of the suspended cargo250(which will be hereinafter referred to as the “weight of the suspended cargo250”), and the “cargo swing” means a swing of the suspended cargo250.

Next, the structure of the slow stopping apparatus2will be described.

As shown inFIG. 4, the slow stopping apparatus2has a structure in which a weight detector50for detecting the weight of the suspended cargo250is added to the slow stopping apparatus1according to the first embodiment.

In the present embodiment, the actuator10is a turning motor for turning the boom230, a derricking cylinder for derricking the boom230, or an expanding/contracting cylinder for expanding/contracting the boom230.

The operating unit30includes an operating lever, an operating pedal, a switch and the like which are provided on a driver's seat of the mobile crane200. The control unit20controls a driving speed of the actuator10in accordance with an operating amount of the operating unit30(an amount of inclination of the operating lever). In the case in which the operating unit30is not operated (the operating amount is 0), moreover, a stop signal for giving an instruction to stop the motion of the boom230is input from the operating unit30to the control unit20.

The posture detector40is configured from various sensors for measuring the turning angle, derricking angle and expansion/contraction length of the boom230and a distance from a tip of the boom230to the suspended cargo250(which will be hereinafter referred to as a “suspension distance of the hook240)”. A result of the detection of the posture detector40is input to the control unit20.

The weight detector50is configured from various sensors for measuring the weight of the suspended cargo250. The result of the detection of the weight detector50is input to the control unit20.

The control unit20includes first slow stopper21, second slow stopper22, cargo swing predictor23, and switcher24and is configured to stop the actuator10which is being driven in their cooperation

Signals are input from the operating unit30, the posture detector40and the weight detector50to the first slow stopper21. The first slow stopper21stops the actuator10by the following slow stopping method when inputting a stop signal for giving an instruction to stop the motion of the boom230from the operating unit30.

First of all, the first slow stopper21calculates a cargo swing cycle T of the suspended cargo250based on the results of the detection of the posture detector40and the weight detector50when inputting the stop signal from the operating unit30. Herein, the cargo swing cycle T represents a cycle of a natural vibration of the suspended cargo250which is generated when the motion of the boom230is stopped suddenly. It is known that the cargo swing cycle T of the suspended cargo250is uniquely determined by the posture of the boom230(the derricking angle and the expansion/contraction length), the suspension distance of the hook240and the weight of the suspended cargo250.

The first slow stopper20has a structure in which information such as a dead weight, a structure or a rigidity about the boom230is prestored and the cargo swing cycle T is dynamically calculated based on the information and the results of the detection of the posture detector40and the weight detector50(the posture of the boom230, the suspension distance of the hook240and the weight of the suspended cargo250).

Moreover, it is also possible to employ a structure in which the cargo swing cycles T for the postures of the boom230, the suspension distances of the hook240and the weights of the suspended cargo250are previously obtained by a test and are stored in the first slow stopper21, and the first slow stopper21calls the cargo swing cycle T corresponding to the results of the detection of the posture detector40and the weight detector50from the cargo swing cycles T for the postures of the boom230, the suspension distances of the hook240and the weights of the suspended cargo250which are stored.

Next, the first slow stopper21outputs a control signal in order to take a time T1(=T/2) in a half of the calculated cargo swing cycle T, thereby braking and stopping the actuator10.

The second slow stopper22inputs signals from the operating unit30, the posture detector40and the weight detector50. The second slow stopper22stops the actuator10by the same slow stopping methods as the second slow stopper22according to the first embodiment when inputting the stop signal from the operating unit30.

Herein, the time T2is set to be shorter than the time T1in the half of the cargo swing cycle T. For this reason, when the actuator10is stopped by the second slow stopper22, the cargo swing occurs corresponding to a shorter portion than the time T1. A value of the time T2is predetermined by a test. More specifically, times required for the stop are obtained to cause the load amplitude to fall within a predetermined range for the postures of the boom130, the suspension distances of the hook240and the weights of the suspended cargo250, and are set to be the times T2.

The second slow stopper22calls the time T2corresponding to the results of the detection of the posture detector40and the weight detector50from the times T2for the postures of the boom130, the suspension distances of the hook240and the weights of the suspended cargo250which are stored, and takes the time T2to output a control signal in order to stop the actuator10.

The time T2may be determined as a constant value regardless of the posture of the boom130, the suspension distance of the hook240and the weight of the suspended cargo250. In this case, the results of the detection of the posture detector40and the weight detector50are not input to the second slow stopper22. The second slow stopper22outputs a control signal so as to take the prestored time T2, thereby stopping the actuator10regardless of the posture of the boom130, the suspension distance of the hook240and the weight of the suspended cargo250.

The cargo swing predictor23inputs signals from the operating unit30, the posture detector40and the weight detector50. The cargo swing predictor23predicts whether the load amplitude in the sudden stop of the motion of the boom230would exceed an allowable value based on the operating amount of the operating unit30and the results of the detection of the posture detector40and the weight detector50. In the present embodiment, the cargo swing predictor23carries out prediction by the following method.

First of all, the cargo swing predictor23calculates the load amplitude A of the suspended cargo250based on the operating amount of the operating unit30and the results of the detection of the posture detector40and the weight detector50. It is known that the load amplitude A of the suspended cargo250is determined by the posture of the boom230(the derricking angle and the expansion/contraction length), the suspension distance of the hook240, the motion speed of the boom230and the weight of the suspended cargo250.

In the present embodiment, the motion speed of the boom230is acquired from the operating amount of the operating unit30. The motion speed of the boom230may be calculated based on a time change in the result of the detection of the posture detector40(the posture of the boom230). Moreover, a speed detector for detecting the motion speed of the boom230may be provided in addition to the operating unit30.

The cargo swing predictor23has a structure in which information such as a structure or a rigidity about the boom230is prestored and the load amplitude A is dynamically calculated based on the information, the operating amount of the operating unit30(the motion speed of the boom230), the results of the detection of the posture detector40and the weight detector50(the posture of the boom230, the suspension distance of the hook240and the weight of the suspended cargo250).

Moreover, it is also possible to employ a structure in which the load amplitudes A for the postures of the boom230, the suspension distances of the hook240, the motion speeds of the boom230and the weights of the suspended cargo250are previously obtained by a test and are stored in the cargo swing predictor23, and the cargo swing predictor23calls the load amplitude A corresponding to the operating amount of the operating unit30and the results of the detection of the posture detector40and the weight detector50from the load amplitudes A for the postures of the boom230, the suspension distances of the hook240, the motion speeds of the boom230and the weights of the suspended cargo250which are stored.

Next, the cargo swing predictor23decides that the load amplitude A would exceed an allowable value when the calculated load amplitude A exceeds a prestored threshold, and decides that the load amplitude A would not exceed the allowable value when the calculated load amplitude A does not exceed the threshold.

Herein, the threshold is predetermined as an allowable maximum value of the load amplitude A. For example, the threshold is determined as a maximum value of the load amplitude A with which the cargo swing of the suspended cargo250can be ensured safely.

The switcher24outputs the control signal of the first slow stopper21to the actuator10to stop the actuator10by the first slow stopper21when the cargo swing predictor23predicts that the load amplitude A would exceed an allowable value. Moreover, the switcher24outputs the control signal of the second slow stopper22to the actuator10, thereby stopping the actuator10by the second slow stopper22when the cargo swing predictor23predicts that the load amplitude A would not exceed the allowable value.

Next, the motion of the slow stopping apparatus2will be described.

As shown inFIG. 2, when the worker operates the operating unit30to change the operating amount of the operating unit30from p to 0 (the non-operation state) at the time t (FIG. 2(a)), the first slow stopper21outputs the control signal to take the time T1in the half of the cargo swing cycle T, thereby stopping the actuator10(FIG. 2(b)). On the other hand, the second slow stopper22outputs the control signal to take the shorter time T2than the time T1, thereby stopping the actuator10(FIG. 2(c)). Moreover, the cargo swing predictor23predicts whether the load amplitude A would exceed the allowable value based on the operating amount p of the operating unit30just before a sudden stop and the results of the detection of the posture detector40and the weight detector50.

In the case in which the expansion/contraction length of the boom230is great, the case in which the motion speed of the boom230is high, the case in which the suspension distance of the hook240is great or the case in which the weight of the suspended cargo250is great, the cargo swing predictor23predicts that the load amplitude A would exceed the allowable value. In this case, the switcher24outputs the control signal of the first slow stopper21to the actuator10to stop the actuator10by the first slow stopper21. For this reason, it is possible to suppress the cargo swing in the stop of the motion of the boom230.

On the other hand, in the case in which the expansion/contraction length of the boom230is small, the case in which the motion speed of the boom230is low, the case in which the suspension distance of the hook240is short or the case in which the weight of the suspended cargo250is small, the cargo swing predictor23predicts that the load amplitude A would not exceed the allowable value. In this case, the switcher24outputs the control signal of the second slow stopper22to the actuator10to stop the actuator10by the second slow stopper22. For this reason, it is possible to shorten a time required for stopping the motion of the boom230. In addition, it is predicted that the load amplitude A would not exceed the allowable value. Even if the actuator10is stopped by the second slow stopper22, therefore, it is possible to control the load amplitude A to fall within an allowable range.

As described above, according to the slow stopping apparatus2, it is possible to shorten the stopping time while suppressing the cargo swing.

Moreover, the cargo swing predictor23according to the present embodiment predicts the load amplitude A based on the operating amount of the operating unit30(the motion speed of the boom230), the result of the detection of the posture detector40(the posture of the boom230and the suspension distance of the hook240) and the weight of the suspended cargo250, and predicts whether the allowable value would be exceeded based on the load amplitude A in the case in which the motion of the boom230having the hook240is stopped. Consequently, it is possible to accurately predict the cargo swing. Therefore, it is possible to properly switch the first slow stopper21and the second slow stopper22, and to shorten the stopping time while suppressing the cargo swing reliably.

Third Embodiment

Next, a slow stopping apparatus3according to a third embodiment of the present invention will be described.

In a mobile crane200, a cargo swing is generated also in the case in which the upward/downward motion of a hook240is stopped in addition to the case of stop of turning, derricking and expanding/contracting motions of the boom230. In more detail, the hook240is moved upward/downward, the boom230is flexed by an inertial force of a suspended cargo250when the upward/downward movement is stopped suddenly, and the suspended cargo250is swung in a perpendicular direction by the flexure. The slow stopping apparatus3according to the present embodiment is used for suppressing the swing of the suspended cargo250when stopping the upward/downward movement of the hook240in the mobile crane200.

A structure of the slow stopping apparatus3is the same as that of the slow stopping apparatus2according to the second embodiment (seeFIG. 4). In the present embodiment, an actuator10is a winch for moving the hook240upward/downward.

An operating unit30includes an operating lever, an operating pedal, a switch and the like which are provided on a driver's seat of the mobile crane200. A control unit20controls the driving speed of the actuator10in accordance with an operating amount of the operating unit30(an amount of inclination of the operating lever). In the case in which the operating unit30is not operated (the operating amount is 0), moreover, a stop signal for giving an instruction to stop the motion of the hook240is input from the operating unit30to the control unit20.

Signals are input from the operating unit30, a posture detector40and a weight detector50to a first slow stopper21. The first slow stopper21stops the actuator10by the following slow stopping method when inputting a stop signal for giving an instruction to stop the motion of the hook240from the operating unit30.

First of all, the first slow stopper21calculates a cargo swing cycle T of the suspended cargo250based on results of detection of the posture detector40and the weight detector50when inputting the stop signal from the operating unit30. Herein, the cargo swing cycle T represents a cycle of a natural vibration of the suspended cargo250which is generated when the motion of the hook240is stopped suddenly. It is known that the cargo swing cycle T of the suspended cargo250is uniquely determined by the posture of the boom230(the derricking angle and the expansion/contraction length) and the weight of the suspended cargo250. The first slow stopper21has such a structure as to dynamically calculate the cargo swing cycle T or to call the prestored cargo swing cycle T.

Next, the first slow stopper21outputs a control signal in order to take a time T1(=T/2) in a half of the calculated cargo swing cycle T, thereby braking and stopping the actuator10.

Signals are input from the operating unit30, the posture detector40and the weight detector50to a second slow stopper22. The second slow stopper22stops the actuator10by the same slow stopping method the second slow stopper22according to the first embodiment when inputting the stop signal from the operating unit30.

Herein, the time T2is set to be shorter than the time T1in the half of the cargo swing cycle T. For this reason, when the actuator10is stopped by the second slow stopper22, the cargo swing occurs corresponding to a shorter portion than the time T1. A value of the time T2is predetermined by a test. More specifically, times required for the stop are obtained to cause the load amplitude to fall within a predetermined range for each posture of a boom130and each weight of the suspended cargo250, and are set to be the times T2.

The second slow stopper22calls the time T2corresponding to the results of the detection of the posture detector40and the weight detector50from the times T2for the postures of the boom130and the weights of the suspended cargo250which are stored, and outputs a control signal to take the time T2, thereby stopping the actuator10.

The time T2may be determined as a constant value regardless of the posture of the boom130and the weight of the suspended cargo250. In this case, the results of the detection of the posture detector40and the weight detector50are not input to the second slow stopper22. The second slow stopper22outputs a control signal so as to take the prestored time T2, thereby stopping the actuator10regardless of the posture of the boom130and the weight of the suspended cargo250.

The cargo swing predictor23inputs signals from the operating unit30, the posture detector40and the weight detector50. The cargo swing predictor23predicts whether the load amplitude in the sudden stop of the motion of the hook240would exceed an allowable value based on the operating amount of the operating unit30and the results of the detection of the posture detector40and the weight detector50. In the present embodiment, the cargo swing predictor23carries out prediction by the following method.

First of all, the cargo swing predictor23calculates a load amplitude A of the suspended cargo250based on the operating amount of the operating unit30and the results of the detection of the posture detector40and the weight detector50. It is known that the load amplitude A of the suspended cargo250is determined by the posture of the boom230(the derricking angle and the expansion/contraction length), the motion speed of the boom230and the weight of the suspended cargo250. The cargo swing predictor23has such a structure as to dynamically calculate the load amplitude A or to call the prestored load amplitude A.

In the present embodiment, the motion speed of the hook240is acquired from the operating amount of the operating unit30. The motion speed of the hook240may be calculated based on a time change in the result of the detection of the posture detector40(the suspension distance of the hook240). Moreover, a speed detector for detecting the motion speed of the hook240may be provided in addition to the operating unit30.

Next, the cargo swing predictor23decides that the load amplitude A would exceed an allowable value when the calculated load amplitude A exceeds a prestored threshold, and decides that the load amplitude A would not exceed the allowable value when the calculated load amplitude A does not exceed the threshold.

The switcher24outputs the control signal of the first slow stopper21to the actuator10to stop the actuator10by the first slow stopper21when the cargo swing predictor23predicts that the load amplitude A would exceed an allowable value. Moreover, the switcher24outputs the control signal of the second slow stopper22to the actuator10, thereby stopping the actuator10by the second slow stopper22when the cargo swing predictor23predicts that the load amplitude A would not exceed the allowable value.

Next, the motion of the slow stopping apparatus2will be described.

As shown inFIG. 2, when a worker operates the operating unit30to change the operating amount of the operating unit30from p to 0 (a non-operation state) at the time t (FIG. 2 (a)), the first slow stopper21outputs a control signal in order to take a time T1in the half of the cargo swing cycle T, thereby stopping the actuator10(FIG. 2 (b)). On the other hand, the second slow stopper22outputs the control signal in order to take the shorter time T2than the time T1, thereby stopping the actuator10(FIG. 2 (c)). Moreover, the cargo swing predictor23predicts whether the load amplitude A would exceed the allowable value based on the operating amount p of the operating unit30just before a sudden stop and the results of the detection of the posture detector40and the weight detector50.

In the case in which the expansion/contraction length of the boom230is great, the case in which the motion speed of the hook240is high or the case in which the weight of the suspended cargo250is great, the cargo swing predictor23predicts that the load amplitude A would exceed the allowable value. In this case, the switcher24outputs the control signal of the first slow stopper21to the actuator10to stop the actuator10by the first slow stopper21. For this reason, it is possible to suppress the cargo swing in the stop of the motion of the boom230.

On the other hand, in the case in which the expansion/contraction length of the boom230is small, the case in which the motion speed of the hook240is low or the case in which the weight of the suspended cargo250is small, the cargo swing predictor23predicts that the load amplitude A would not exceed the allowable value. In this case, the switcher24outputs the control signal of the second slow stopper22to the actuator10to stop the actuator10by the second slow stopper22. For this reason, it is possible to shorten a time required for stopping the motion of the boom230. In addition, it is predicted that the load amplitude A would not exceed the allowable value. Even if the actuator10is stopped by the second slow stopper22, therefore, it is possible to control the load amplitude A to fall within an allowable range.

As described above, according to the slow stopping apparatus3, it is possible to shorten the stopping time while suppressing the cargo swing.

Moreover, the cargo swing predictor23according to the present embodiment predicts the load amplitude A based on the operating amount of the operating unit30(the motion speed of the hook240), the result of the detection of the posture detector40(the posture of the boom230) and the weight of the suspended cargo250, and predicts whether the allowable value would be exceeded based on the load amplitude A in the case in which the motion of the hook240is stopped. Consequently, it is possible to accurately predict the cargo swing. Therefore, it is possible to properly switch the first slow stopper21and the second slow stopper22, and to shorten the stopping time while suppressing the cargo swing reliably.

Fourth Embodiment

Next, a slow stopping apparatus4according to a fourth embodiment of the present invention will be described.

The slow stopping apparatus4according to the present embodiment has a configuration in which a predicting method of cargo swing predictor23is different from that in each of the embodiments described above. Since the other structures are the same as those of the slow stopping apparatus1,2or3according to the first, second or third embodiment, description will be omitted.

The cargo swing predictor23according to the present embodiment decides that a load amplitude A would exceed an allowable value when an operating amount p of the operating unit30just before a sudden stop (a motion speed of a boom130or230or a hook240) exceeds a threshold, and decides that the load amplitude A would not exceed the allowable value when the operating amount p of the operating unit30just before a sudden stop does not exceed the threshold. Herein, the thresholds are predetermined for each posture of the boom130or230, suspension distances of the hook240(the case in which the boom230having the hook240is stopped) and weights of a cargo (a bucket140or a suspended cargo250). In other words, the cargo swing predictor23calls a threshold corresponding to results of detection of a posture detector40and a weight detector50from thresholds for the postures of the boom130or230, the suspension distances of the hook240(the case in which the boom230having the hook240is stopped) and weights of cargos140and250which are stored, and compares the threshold with the operating amount p of the operating unit30just before a sudden stop to decide whether the load amplitude A would exceed an allowable value.

The threshold may be determined for each weight of the cargos140and250regardless of the posture of the boom130or230or the suspension distance of the hook240. In this case, the result of the detection of the posture detector40is not input to the cargo swing predictor23. The cargo swing predictor23calls a threshold corresponding to the result of the detection of the weight detector50from the thresholds for the weights of the cargos140and250which are stored, and compares the threshold with the operating amount p of the operating unit30just before a sudden stop, thereby deciding whether the load amplitude A would exceed the allowable value.

Moreover, the thresholds may be determined for the postures of the booms130and230and the suspension distances of the hook240(the case in which the boom230having the hook240is stopped) regardless of each of the weights of the cargos140and250. In this case, the result of the detection of the weight detector50is not input to the cargo swing predictor23. The cargo swing predictor23calls a threshold corresponding to the result of the detection of the posture detector40from the thresholds for the postures of the booms130and230and the suspension distances of the hook240(the case in which the boom230having the hook240is stopped) which are stored, and compares the threshold with the operating amount p of the operating unit30just before a sudden stop, thereby deciding whether the load amplitude A would exceed the allowable value.

Furthermore, the threshold may be determined as a constant value regardless of each of the postures of the booms130and230, the suspension distances of the hook240and the weights of the cargos140and250. In this case, the results of the detection of the posture detector40and the weight detector50are not input to the cargo swing predictor23. The cargo swing predictor23compares the prestored threshold with the operating amount p of the operating unit30just before a sudden stop regardless of each of the postures of the booms130and230, the suspension distance of the hook240, and the weights of the cargos140and250, thereby deciding whether the load amplitude A would exceed the allowable value.

By comparison of the operating amount p of the operating unit30just before a sudden stop with the threshold as described above, it is predicted whether the load amplitude A would exceed the allowable value. For this reason, the first slow stopper21and the second slow stopper22are switched based on the motion speeds of the booms130and230. Therefore, a worker can predict either of the slow stopper21and22by which the boom130or230is stopped. Thus, operability can be improved.

In place of the operating amount p of the operating unit30just before a sudden stop, it is also possible to use a result of detection of a speed detector for detecting the motion speed of the boom130or230or the hook240. It is also possible to calculate the motion speed of the boom230or the hook240based on a time change in the result of the detection of the posture detector40(the posture of the boom230or the suspension distance of the hook240).

Fifth Embodiment

Next, a slow stopping apparatus5according to a fifth embodiment of the present invention will be described.

In the embodiments, the cargo swing predictor23may be configured in the following manner.

The cargo swing predictor23decides that a load amplitude A would exceed an allowable value when a result of detection of a posture detector40exceeds a threshold, and decides that the load amplitude A would not exceed the allowable value when the result of the detection of the posture detector40does not exceed the threshold. Herein, the threshold is predetermined for each motion speed of a boom130or230or a hook240and each weight of a cargo140or250. In other words, the cargo swing predictor23calls a threshold corresponding to an operating amount p of the operating unit30just before a sudden stop (the motion speed of the boom130or230or the hook240) and a result of detection of a weight detector50, and compares the threshold with the result of the detection of the posture detector40, thereby deciding whether the load amplitude A would exceed the allowable value.

The threshold may be determined for each of the weights of the cargos140and250regardless of the motion speed of the boom130or230or the hook240. In this case, the operating amount of the operating unit30is not input to the cargo swing predictor23. The cargo swing predictor23calls a threshold corresponding to the result of the detection of the weight detector50from the thresholds for the weights of the cargos140and250which are stored, and compares the threshold with the result of the detection of the posture detector40, thereby deciding whether the load amplitude A would exceed the allowable value.

Moreover, the threshold may be determined for each motion speed of the boom130or230or the hook240regardless of the weight of the cargo140or250. In this case, the result of the detection of the weight detector50is not input to the cargo swing predictor23. The cargo swing predictor23calls a threshold corresponding to the operating amount p of the operating unit30just before a sudden stop (the motion speed of the boom130or230or the hook240) from the thresholds for the motion speed of the boom130or230or the hook240which are stored, and compares the threshold with the result of the detection of the posture detector40, thereby deciding whether the load amplitude A would exceed the allowable value.

Furthermore, the threshold may be determined as a constant value regardless of the motion speed of the boom130or230or the hook240and the weight of the cargo140or250. In this case, neither the operating amount of the operating unit30nor the result of the detection of the weight detector50are input to the cargo swing predictor23. The cargo swing predictor23compares the prestored threshold with the result of the detection of the posture detector40regardless of the motion speed of the boom130or230or the hook240and the weight of the cargo140or250, thereby deciding whether the load amplitude A would exceed the allowable value.

By comparison of the result of the detection of the posture detector40with the threshold as described above, it is predicted whether the load amplitude A would exceed the allowable value. For this reason, the first slow stopper21and the second slow stopper22are switched based on the posture of the boom130or230. Therefore, a worker can predict either of the slow stopper21and22by which the boom130or230or the hook240is stopped. Thus, operability can be improved.

Sixth Embodiment

Next, a slow stopping apparatus6according to a sixth embodiment of the present invention will be described.

In the embodiments, the cargo swing predictor23may be configured in the following manner.

The cargo swing predictor23decides that a load amplitude A would exceed an allowable value when a result of detection of a weight detector50exceeds a threshold, and decides that the load amplitude A would not exceed the allowable value when the result of the detection of the weight detector50does not exceed the threshold. Herein, the threshold is predetermined for each posture of a boom130or230, each suspension distance of a hook240(the case in which the boom230having the hook240is stopped), and each motion speed of the boom130or230or the hook240. In other words, the cargo swing predictor23calls a threshold corresponding to a result of detection of a posture detector40and an operating amount p of the operating unit30just before a sudden stop (the motion speed of the boom130or230or the hook240) from thresholds for the postures of the boom130or230, the suspension distances of the hook240(the case in which the boom230having the hook240is stopped) and the motion speeds of the boom130or230or the hook240which are stored, and compares the threshold with the result of the detection of the weight detector50, thereby deciding whether the load amplitude A would exceed the allowable value.

The threshold may be determined for each motion speed of the boom130or230or the hook240regardless of the posture of the boom130or230or the suspension distance of the hook240. In this case, the result of the detection of the posture detector40is not input to the cargo swing predictor23. The cargo swing predictor23calls a threshold corresponding to the operating amount p of the operating unit30just before a sudden stop (the motion speed of the boom130or230or the hook240) from the thresholds for the motion speeds of the boom130or230or the hook240which are stored, and compares the threshold with the result of the detection of the weight detector50, thereby deciding whether the load amplitude A would exceed the allowable value.

Moreover, the threshold may be determined for each posture of the boom130or230and each suspension distance of the hook240(the case in which the boom230having the hook240is stopped) regardless of the motion speed of the boom130or230or the hook240. In this case, the operating amount of the operating unit30is not input to the cargo swing predictor23. The cargo swing predictor23calls a threshold corresponding to the result of the detection of the posture detector40from the thresholds for the postures of the booms130and230and the suspension distances of the hook240which are stored (the case in which the boom230having the hook240is stopped), and compares the threshold with the result of the detection of the weight detector50, thereby deciding whether the load amplitude A would exceed the allowable value.

Furthermore, the threshold may be determined as a constant value regardless of the posture of the boom130or230, the suspension distance of the hook240, and the motion speed of the boom130or230or the hook240. In this case, the result of the detection of the posture detector40and the operating amount of the operating unit30are not input to the cargo swing predictor23. The cargo swing predictor23compares the prestored threshold with the result of the detection of the weight detector50regardless of the posture of the boom130or230, the suspension distance of the hook240and the motion speed of the boom130or230or the hook240, thereby deciding whether the load amplitude A would exceed the allowable value.

By comparison of the result of the detection of the weight detector50with the threshold as described above, it is predicted whether the load amplitude A would exceed the allowable value. For this reason, the first slow stopper21and the second slow stopper22are switched based on the weights of the cargos140and250. Therefore, a worker can predict either of the slow stopper21and22by which the boom130or230or the hook240is stopped. Thus, operability can be improved.

Other Embodiments

In combination of the structures according to the fourth, fifth and sixth embodiments, furthermore, the cargo swing predictor23may be configured to decide whether the load amplitude A would exceed the allowable value by comparing the operating amount p of the operating unit30just before a sudden stop (the motion speed of the boom130or230or the hook240), the results of the detection of the posture detector40and the weight detector50and the prestored threshold.

In the fifth and sixth embodiments, moreover, it is also possible to use a result of detection of a speed detector for detecting the motion speed of the boom130or230or the hook240in place of the operating amount p of the operating unit30just before a sudden stop. The motion speed of the boom230or the hook240may be calculated based on a time change in the result of the detection of the posture detector40(the posture of the boom230or the suspension distance of the hook240).

In each of the embodiments, moreover, it is also possible to provide a display for displaying the first slow stopper21or the second slow stopper22which slowly stops the actuator10. The display preferably has a structure in which the display is switched based on the result of the prediction of the cargo swing predictor23.

EXPLANATION OF DESIGNATION