WO2021085566A1 - Overload prevention device - Google Patents

Abstract

This overload prevention device is built into a crane that has a boom and that transports a suspended load, and comprises: a storage unit that stores a first threshold value that is set as the upper limit of a load that will not cause the crane to tip forward; and a control unit that performs overload prevention control, including control for stopping the operation of the boom and/or control for issuing an alarm, when a forward load that generates the forward moment acting on the boom is greater than the first threshold value.

Description

Overload prevention device

The present invention relates to an overload prevention device for a crane. More specifically, the present invention relates to an overload prevention device for preventing a fall due to an overload of a crane.

There is a crane overload prevention device that detects a fall based on the ground reaction force of the outrigger jack. As the overturning moment of the mobile crane increases, the ground contact reaction force of the outrigger jack provided on the overturning side decreases accordingly. Utilizing this, the overload prevention device determines that the outrigger jack is overloaded when the ground contact reaction force of the outrigger jack becomes equal to or less than the threshold value.

In the case of a loaded truck crane, the outrigger jack is installed almost right next to the turning center of the boom. In such a configuration, the ground reaction force of the outrigger jack does not change even if the forward overturning moment increases. Therefore, it is not possible to detect a forward fall based on the ground contact reaction force of the outrigger jack.

On the other hand, Patent Document 1 discloses a technique for detecting a forward fall based on the fact that the actual load reaches the allowable forward lifting load. The permissible forward lifting load is obtained from the forward overturning moment at the limit where the rear wheels of the truck are lifted in the boom front work in which the telescopic boom is swiveled to the front of the truck in an empty state where no load is loaded on the truck bed.

Japanese Unexamined Patent Publication No. 2008-105817

The permissible forward lifting load of Patent Document 1 is obtained from the forward overturning moment in the state where the boom is most likely to overturn toward the front. Therefore, when the boom is directed diagonally forward, the loaded truck crane will not tip over even if the actual load exceeds the allowable forward lifting load to some extent. In other words, when the boom is directed diagonally forward, the operation of the crane device is restricted even though there is room for a fall. This means that the working range in front of the crane equipment is unnecessarily limited.

In view of the above circumstances, an object of the present invention is to provide a crane overload prevention device capable of expanding the working range in front of the crane.

One aspect of the overload prevention device according to the present invention is
An overload prevention device that has a boom and is built into a crane that transports suspended loads.
A storage unit that stores the first threshold value set as the upper limit of the load that prevents the crane from tipping forward,
A control unit that performs overload prevention control including at least one of control for stopping the operation of the boom and control for issuing an alarm when the forward load that generates the forward moment acting on the boom is larger than the first threshold value. And.

One aspect of the overload prevention device according to the present invention is
An overload prevention device that has a boom and is built into a crane that transports suspended loads.
Based on the forward load that generates the forward moment acting on the boom, the first determination unit that determines whether the crane is in a forward overload state, and
The second judgment unit that determines whether the crane is overloaded with respect to the side, and
A third judgment unit that determines whether the crane is overloaded with respect to strength,
When the judgment result of at least one of the first judgment unit, the second judgment unit, and the third judgment unit is an overload state, the control for stopping the operation of the boom and the control for issuing an alarm are performed. A control unit that performs overload prevention control including at least one control is provided.

According to the present invention, since the overload is determined based on the forward overturning component of the overturning moment acting on the boom, the working range when the boom is directed diagonally forward can be expanded.

FIG. 1 is a side view of a loaded truck crane. FIG. 2 is a plan view of a loaded truck crane. FIG. 3 is a hydraulic circuit diagram of a small crane. FIG. 4 is an explanatory view of the forward working range. FIG. 5 is a block diagram of the overload prevention device according to the first embodiment. FIG. 6 is a flowchart of control of the forward stability monitoring unit according to the first embodiment. FIG. 7 is a flowchart of control of the forward stability monitoring unit according to the second embodiment.

Next, an embodiment of the present invention will be described with reference to the drawings. [First Embodiment]
The overload prevention device AA according to the first embodiment of the present invention is used to prevent the mobile crane from tipping over due to overload. Mobile cranes include all-terrain cranes, rough terrain cranes, truck cranes, and loaded truck cranes. Among these, the overload prevention device AA of the present embodiment is preferably used for a load-type truck crane.

(Load type truck crane)
First, the loading type truck crane CR will be described. As shown in FIG. 1, the load-type truck crane CR has a general-purpose truck 10. A driver's cab 11 is provided in the front portion of the general-purpose truck 10, and a loading platform 12 is provided in the rear portion. A small crane 20 is mounted in a portion of the vehicle frame 13 of the general-purpose truck 10 between the driver's cab 11 and the loading platform 12.

The small crane 20 has a base 21 fixed on the vehicle frame 13. A post 22 is provided on the base 21 so as to be rotatable. A boom 23 is provided on the upper end of the post 22 so as to be undulating. The post 22 has a built-in winch. The wire rope extended from this winch is guided to the tip of the boom 23. The wire rope is hung around a pulley provided at the tip of the boom 23 and the hook 24. As a result, the hook 24 is suspended from the tip of the boom 23. A suspended load is suspended from the hook 24.

A device composed of a post 22, a boom 23, a hook 24, etc. and used for transporting a suspended load is referred to as a "crane device". The boom 23 can be expanded and contracted and undulated, and can be swiveled around the swivel center O. In this specification, the length of the boom 23 is referred to as L. The undulation angle (angle with respect to the horizontal plane) of the boom 23 is expressed as φ. Further, as shown in FIG. 2, the turning angle of the boom 23 is referred to as θ. The turning angle θ is 0 ° directly in front of the loaded truck crane CR.

The small crane 20 has an outrigger jack 25 in addition to the crane device. The outrigger jacks 25 are arranged on the left and right sides of the small crane 20. The left and right outrigger jacks 25 and the turning center O of the boom 23 are arranged side by side in the vehicle width direction. That is, the left and right outrigger jacks 25 and the turning center O of the boom 23 are arranged at the same position in the front-rear direction of the general-purpose truck 10 or are arranged at short distances. An outrigger jack different from the outrigger jack 25 may be provided on the left and right rear of the loading platform 12.

The small crane 20 is hydraulically driven by the hydraulic circuit 30 shown in FIG. The hydraulic circuit 30 has a hydraulic valve unit 31. The inlet port of the hydraulic valve unit 31 is connected to the tank 32 via the main oil passage 34. A hydraulic pump 33 is provided in the main oil passage 34. The hydraulic pump 33 is connected to the engine 14 of the general-purpose truck 10 via a PTO (power take-off) device, and is driven by the engine 14. The hydraulic oil in the tank 32 is supplied to the hydraulic valve unit 31 by the hydraulic pump 33. The outlet port of the hydraulic valve unit 31 is connected to the tank 32 via the return oil passage 35.

A plurality of hydraulic actuators 36a to 36f are connected to the hydraulic valve unit 31. The hydraulic actuators 36a to 36f are a boom expansion / contraction hydraulic cylinder 36a, a winch hydraulic motor 36b, a boom undulating hydraulic cylinder 36c, a swivel hydraulic motor 36d, and an outrigger hydraulic cylinders 36e and 36f. The boom 23 expands and contracts due to the operation of the boom expansion and contraction hydraulic cylinder 36a. The hook 24 is hoisted and unwound by the operation of the winch hydraulic motor 36b. The boom 23 undulates due to the operation of the boom undulating hydraulic cylinder 36c. The post 22 is swiveled by the operation of the swivel hydraulic motor 36d. The outrigger jack 25 expands and contracts due to the operation of the outrigger hydraulic cylinders 36e and 36f.

The hydraulic valve unit 31 is provided with a telescopic switching control valve 37a, a winch switching control valve 37b, an undulating switching control valve 37c, a swivel switching control valve 37d, and outrigger switching control valves 37e and 37f. A boom expansion / contraction hydraulic cylinder 36a is connected to the expansion / contraction switching control valve 37a. A winch hydraulic motor 36b is connected to the winch switching control valve 37b. A boom undulating hydraulic cylinder 36c is connected to the undulating switching control valve 37c. A swivel hydraulic motor 36d is connected to the swivel switching control valve 37d. The outrigger hydraulic cylinders 36e and 36f are connected to the outrigger switching control valves 37e and 37f, respectively. The switching control valves 37a to 37f control the direction and flow rate of the hydraulic oil supplied from the hydraulic pump 33 to control the operation of the hydraulic actuators 36a to 36f.

An operation lever is connected to the spools of the switching control valves 37a to 37f via a link mechanism or the like. By manually operating the operating lever, the spool positions of the switching control valves 37a to 37f can be switched. That is, the switching control valves 37a to 37f can be directly operated by the operating lever.

As shown in FIG. 1, the small crane 20 has an operating lever group 26. The operating levers constituting the operating lever group 26 are connected to any of the switching control valves 37a to 37f. The operator can operate the small crane 20 by using the operating lever group 26.

As shown in FIG. 3, pilot cylinders 38a to 38f are attached to the spools of the switching control valves 37a to 37f, respectively. The spool positions of the switching control valves 37a to 37f can also be switched by the operation of the pilot cylinders 38a to 38f.

Each of the pilot cylinders 38a to 38f is a double-acting cylinder, and is provided with a solenoid valve for supplying and discharging hydraulic oil to the right oil chamber and an electromagnetic valve for supplying and discharging hydraulic oil to the left oil chamber. There is. These solenoid valves are connected to the control device 40.

The control device 40 is a computer composed of a CPU, a memory, and the like. By operating the solenoid valve based on the control signal from the control device 40, the pilot cylinders 38a to 38f are driven, and the spool positions of the switching control valves 37a to 37f are switched. In this way, the control device 40 controls the operation of the small crane 20.

The control device 40 can perform bidirectional wireless communication or wired communication with the remote control terminal 41. The remote control terminal 41 may be a wireless control terminal such as a so-called radio control transmitter, or a wired control terminal. The remote control terminal 41 is equipped with an input unit including various switches and an accelerator trigger.

When the operator operates the input unit of the remote control terminal 41, the remote control terminal 41 transmits an operation signal to the control device 40. The control device 40 controls the hydraulic circuit 30 based on the operation signal to operate the small crane 20. In this way, the operator can remotely control the small crane 20 using the remote control terminal 41.

The small crane 20 has an attitude measuring device that measures the attitude of the boom 23. In the case of the present embodiment, the posture of the boom 23 is represented by the length L of the boom 23, the undulation angle φ, and the turning angle θ. The posture measuring instrument consists of a plurality of measuring instruments that measure each of these parameters L, φ, and θ. That is, the posture measuring device includes a length measuring device 42, an undulation angle measuring device 43, and a turning angle measuring device 44.

The length measuring device 42 measures the length L of the boom 23. The configuration of the length measuring instrument 42 is not particularly limited, and examples thereof include a configuration in which the rotation angle of the cord reel in which the end of the cord is fixed to the tip of the boom 23 is read by a potentiometer.

The undulation angle measuring device 43 measures the undulation angle φ of the boom 23. The configuration of the undulation angle measuring device 43 is not particularly limited, and examples thereof include a configuration in which a pendulum type angle measuring device in which a pendulum is attached to a potentiometer is provided on the boom 23.

The turning angle measuring device 44 measures the turning angle θ of the boom 23. The configuration of the swivel angle measuring device 44 is not particularly limited, but in addition to a configuration in which the swivel angle θ of the boom 23 is discretely detected by a plurality of proximity switches provided on the base 21 or the post 22, a hydraulic motor that swivels the post 22 An example is a configuration in which the rotation angle is read by a potentiometer.

Further, the small crane 20 has a load measuring device 45 that measures the load W of the suspended load suspended from the hook 24. The configuration of the load measuring device 45 is not particularly limited, but the load is obtained by measuring the hydraulic pressure in the boom undulating hydraulic cylinder 36c that raises and lowers the boom 23 with a pressure sensor, and from the tension of the wire rope that suspends the hook 24. An example is a configuration using a tension detector that detects a load W.

(Overload prevention device)
Next, the overload prevention device AA of the present embodiment will be described. The control device 40 has a function as an overload prevention device AA in addition to a function of controlling the operation of the small crane 20. The overload prevention device AA may be configured by a computer different from the control device 40.

As shown in FIG. 5, the measurement values of the posture measuring device (length measuring device 42, undulation angle measuring device 43, turning angle measuring device 44) and the load measuring device 45 are input to the overload prevention device AA. .. That is, the overload prevention device AA is input with the measured values _{of the length L d} of the boom 23, the undulation angle φ _d, and the turning angle θ _d , and the measured values of the load W _{d of the suspended load.}

The overload prevention device AA detects the overload state of the small crane 20 based on _{these measured values L d} , φ _d , θ _d , and W _d. Here, the "overload state" is a state in which the overload moment exceeds the stable moment and the load-type truck crane CR overturns, and the load due to the load W of the suspended load exceeds the load capacity of the constituent members of the small crane 20. It means a state or a state approaching those states.

The overload prevention device AA has a front stability monitoring unit 51, a side stability monitoring unit 52, and a strength limit monitoring unit 53. The forward stability monitoring unit 51 corresponds to an example of the control unit and the first determination unit, and monitors whether or not the loaded truck crane CR falls forward, that is, the stability in the forward direction. The lateral stability monitoring unit 52 corresponds to an example of the second determination unit and monitors whether or not the loaded truck crane CR falls sideways, that is, lateral stability. The strength limit monitoring unit 53 corresponds to an example of the third determination unit, and monitors whether or not the load due to the load of the suspended load exceeds the withstand load of the constituent members. Hereinafter, each control will be described in order.

(Forward stability monitoring)
First, the principle of forward stability monitoring will be described. When the length of the boom 23 is L and the undulation angle is φ, the working radius R is calculated by the equation (1).

Assuming that the load of the suspended load suspended on the hook 24 is W, the magnitude M of the overturning moment acting on the boom 23 by the suspended load W is calculated by the equation (2). A moment generated by the weight of the boom 23 may be added to the overturning moment M.

Here, as shown in FIG. 2, it is assumed that the boom 23 is turning diagonally forward. In this case, of the overturning moment acting on the boom 23, the magnitude M _f of the forward overturning component is obtained by the equation (3). Hereinafter, M _f is referred to as "forward moment".

_{The maximum value of the forward moment M f} that ensures the forward stability of the loaded truck crane CR is defined as the forward rated moment M _f-lim . The forward rated moment M _f-lim is a predetermined value. The front rated moment M _f-lim means that, for example, the rear wheel of the general-purpose truck 10 is lifted when the boom 23 faces directly in front of the general-purpose truck 10 in an empty state where no load is loaded on the loading platform 12 and the general-purpose truck 10 is most likely to fall forward. It is set to the magnitude of the limit overturning moment. The value obtained by multiplying the magnitude of the critical overturning moment by the safety factor (value less than 1) may be the _{forward rated moment M f-lim.} Further, a predetermined ratio (for example, 25%) of the magnitude of the lateral stabilizing moment may be set as the _{forward rated moment M f-lim with reference to the lateral stabilizing moment of the loaded truck crane CR.}

By comparing the forward moment M _f and the forward rated moment M _f-lim , it can be determined whether or not the loaded truck crane CR falls forward. Specifically, when the forward moment M _f is equal to or less than the forward rated moment M _f-lim , it is determined that the vehicle does not tip forward. If the forward moment M _f exceeds the forward rated moment M _f-lim , it is determined that the vehicle falls forward (overload).

As shown in FIG. 4, when it is uniformly determined that the overload is overloaded based on the fact that the load W of the suspended load reaches the threshold value, the front working range R1 becomes a semi-circular region. On the other hand, as described above, _{when the overload is determined based on the forward overturning component M f} of the overturning moment acting on the boom 23, the front working range R2 is a horizontally long region including the working range R1. .. As described above, according to the above method, the working range when the boom 23 is directed diagonally forward can be expanded.

Based on the above principle, the forward stability monitoring unit 51 of the present embodiment performs the following control. The front stability monitoring unit 51 stores the front rated load W _f-lim (L, φ) in advance. Therefore, the forward stability monitoring unit 51 also has a function as a storage unit. The front rated load W _f-lim corresponds to an example of the first threshold value, and the length L of the boom 23 and the undulations so as to be the load W of the suspended load when the _{front rated moment M f-lim acts on the boom 23.} It is a value determined for each angle φ. The front rated load W _f-lim may be stored in a table format, or may be stored as a function with the length L of the boom 23 and the undulation angle φ as variables. The first threshold is preset as an upper limit of the load that prevents the crane from tipping forward.

_{As shown in FIG. 6, first, the forward stability monitoring unit 51 has measured values L d} , φ _d , θ _d , from the length measuring device 42, the undulation angle measuring device 43, the turning angle measuring device 44, and the load measuring device 45. Acquire W _d (step S11).

Next, the forward stability monitoring unit 51 confirms that the boom 23 is arranged in the front region of the loaded truck crane CR (step S12). The fact that the boom 23 is arranged in the front region means that the tip end portion (hook 24) of the boom 23 is arranged in front of the forward tipping baseline. The forward overturning baseline is, for example, a line connecting the grounding positions of the left and right outrigger jacks 25. When the left and right outrigger jacks 25 are arranged right next to the turning center O _{, the boom 23 is arranged in the front region when the turning angle θ d} of the boom 23 is within the range of −90 ° to + 90 °. You can judge that there is. In other words, the state in which the boom 23 is arranged in the front region means a state in which the magnitude of the forward moment acting on the boom 23 is greater than 0 based on the load W of the suspended load.

If the boom 23 is not located in the front area, the process ends. On the other hand, when the boom 23 is arranged in the front region, the process is continued.

Next, the forward stability monitoring unit 51 _{obtains the forward load W f} (step S13). The forward load W _f is obtained by the following procedure. First, the forward stability monitoring unit 51 obtains the forward ratio from _{the measured value θ d of the turning angle.} Here, the forward ratio is the ratio of the forward moment M _f to the magnitude M of the overturning moment acting on the boom 23. That is, the forward ratio is the cosine value (cos θ _{d ) of the turning angle θ d} (see equation (3)).

The overturning moment has a forward moment M _f and a lateral moment as components. When the length and undulation angle of the boom 23 are fixed, when the turning angle of the boom 23 is 0 °, the forward moment M _f of the overturning moment becomes the maximum, and the turning angle of the boom 23 is 90 ° or −90 °. In the case of, the forward moment M _f of the overturning moment becomes the minimum. The forward moment is a moment acting on the boom 23, and means a moment around an axis parallel to the left-right direction of the loaded truck crane CR. Further, the lateral moment is a moment acting on the boom 23, and means a moment around an axis parallel to the front-rear direction of the loaded truck crane CR.

Next, the front stability monitoring unit 51 obtains the front load W _{f by multiplying the measured load value W d} by the front ratio (cos θ _{d) according to the equation (4).} The forward load W _f is the load W of the suspended load required to generate the overturning moment M equivalent _{to the forward moment M f} , assuming that the boom 23 is arranged directly in front of the boom 23. In other words, the forward load W _f corresponds to the load that generates the forward moment acting on the boom 23 in the measured value W _{d of the load.}

 

Next, the front stability monitoring unit 51 acquires the _{front rated load W f-lim} (L _d , φ _d ), which is the first threshold value corresponding to the _{measured values L d} and φ _d of the length and undulation angle of the boom 23. (Step S14). Then, the front stability monitoring unit 51 _{compares the front load W f} with the front rated load W _f-lim (L _d , φ _d ) (step S15). Then, when the front load W _f exceeds the front rated load W _f-lim (L _d , φ _d ), the front stability monitoring unit 51 determines that the load is overloaded (step S16). Further, the forward stability monitoring unit 51 implements overload prevention control including at least one of control of stopping the operation of the boom 23 and control of issuing an alarm when it is determined that the load is overloaded. The overload prevention control may include a control other than a control for stopping the operation of the boom 23 and a control for issuing an alarm.

(Side stability monitoring)
Next, lateral stability monitoring will be described.
The lateral stability monitoring unit 52 determines that the load is overloaded when the load-type truck crane CR falls under the condition of falling sideways, or when such a condition is approached. The specific control of the lateral stability monitoring unit 52 is not particularly limited, but for example, the following control is performed.

When the lateral overturning moment of the loaded truck crane CR (that is, the lateral moment of the overturning moment acting on the boom 23) increases, the ground reaction force F of the outrigger jack 25 provided on the inverted overturning side accordingly. Becomes smaller. This is used to monitor lateral stability.

The load-type truck crane CR has a ground reaction force measuring device 46 that measures the ground reaction force F of the left and right outrigger jacks 25. The configuration of the ground reaction force measuring device 46 is not particularly limited, and examples thereof include a configuration using a hydraulic sensor that measures the oil pressure in the oil chamber of the outrigger jack 25. The ground contact reaction force F can be calculated from the differential pressure between the holding side oil chamber and the non-holding side oil chamber of the outrigger jack 25 and the pressure receiving area of the jack cylinder.

As shown in FIG. 5, the measurement values of the ground reaction force measuring device 46, i.e., the ground reaction force F _d outrigger jacks 25 are input to the overload prevention device AA. The lateral stability monitoring unit 52 determines that the load is overloaded when _{the ground contact reaction force F d} of any of the left and right outrigger jacks 25 falls below the reaction force threshold value F _lim. The reaction force threshold value F _lim corresponds to an example of the lateral threshold value, and is a value preset in the lateral stability monitoring unit 52. The reaction force threshold value F _lim may be a fixed value of 1, or may be variable based on the posture L, φ, θ of the boom 23, the load W of the suspended load, the overhang width of the outrigger jack 25, and the like.

The lateral stability monitoring unit 52 performs lateral stability monitoring at least when the boom 23 is arranged in the lateral region. The fact that the boom 23 is arranged in the lateral region means that the tip end portion (hook 24) of the boom 23 is arranged laterally from the lateral tipping baseline. The front area and the side area of the boom 23 partially overlap each other diagonally in front of the loaded truck crane CR. Further, when performing lateral stability monitoring based on the ground contact reaction force F of the outrigger jack 25, the side stability monitoring unit 52 may always perform lateral stability monitoring regardless of the turning angle θ of the boom 23. Therefore, when the boom 23 is arranged in the front region, lateral stability monitoring is performed as well as forward stability monitoring. Even if the front stability monitoring unit 51 does not determine that it is overloaded, the side stability monitoring unit 52 may determine that it is overloaded.

(Strength limit monitoring)
Next, the strength limit monitoring will be described. The strength limit monitoring unit 53 determines that the load is overloaded when the load due to the load W of the suspended load exceeds the withstand load of the constituent members. The specific control of the strength limit monitoring unit 53 is not particularly limited, but for example, the following control is performed.

_{The strength rated load W s-lim} (L, φ) is stored in advance in the strength limit monitoring unit 53. The strength rated load W _s-lim is a value determined for each of the length L of the boom 23 and the undulation angle φ as the load capacity of the constituent members such as the boom 23. The length L and the undulation angle φ of the boom 23 correspond to an example of the posture condition of the boom 23. The strength rated load W _s-lim may be stored in a table format, or may be stored as a function with the length L of the boom 23 and the undulation angle φ as variables. The strength rated load W _s-lim may be a value determined for each of the length L of the boom 23, the undulation angle φ, and the turning angle θ.

First, the strength limit monitoring unit 53 acquires the _{measured values L d} , φ _d , and W _d from the length measuring device 42, the undulation angle measuring device 43, and the load measuring device 45. Next, the strength limit monitoring unit 53 acquires the strength rated load W _s-lim (L _d , φ _{d ) corresponding to the measured values L d} and φ _d of the length and undulation angle of the boom 23. Then, the strength limit monitoring unit 53 compares the _{load W d} with the rated strength load W _s-lim (L _d , φ _d). Then, when the load W _d exceeds the strength rated load W _s-lim (L _d , φ _d ), it is determined to be an overload.

The strength limit monitoring unit 53 constantly monitors the strength limit regardless of the turning angle θ of the boom 23.

(Final judgment)
As shown in FIG. 5, the overload prevention device AA has a final determination unit 54. The determination results of the front stability monitoring unit 51, the side stability monitoring unit 52, and the strength limit monitoring unit 53 are input to the final determination unit 54. The final determination unit 54 obtains the logical sum of the determination results of the front stability monitoring unit 51, the side stability monitoring unit 52, and the strength limit monitoring unit 53, and finally determines the overload. That is, when any one or more of the front stability monitoring unit 51, the side stability monitoring unit 52, and the strength limit monitoring unit 53 determines that the load is overloaded, the final determination unit 54 determines that the load is overloaded. On the contrary, when none of the front stability monitoring unit 51, the side stability monitoring unit 52, and the strength limit monitoring unit 53 determines that the load is overloaded, the final determination unit 54 determines that the load is not overloaded.

The determination result of the final determination unit 54 is output to the control device 40. When the determination result is an overload, the control device 40 may automatically stop the operation of the boom 23 or issue an alarm. The automatic stop is performed by stopping the operation of the boom 23 in the direction in which the overturning moment increases. That is, it stops the extension and lodging of the boom 23 and allows the boom 23 to contract and stand. Further, the winding of the hook 24 may be stopped and the winding of the hook 24 may be allowed. Either one of the automatic stop and the alarm may be performed, or both may be performed.

[Second Embodiment]
Next, the overload prevention device AA according to the second embodiment of the present invention will be described.
The configuration of the overload prevention device AA of the present embodiment is the same as the configuration shown in FIG. Further, the control of the lateral stability monitoring unit 52, the strength limit monitoring unit 53, and the final determination unit 54 is the same as in the first embodiment. Therefore, only the control of the forward stability monitoring unit 51 will be described.

The front stability monitoring unit 51 stores the front rated load W _f-lim (L, φ, θ) in advance. The forward rated load W _f-lim corresponds to an example of the first threshold value, and the load W of the suspended load when the forward moment acting on the boom 23 (forward overturning component of the overturning moment) becomes the forward rated moment M _f-lim. It is a value determined for each of the length L of the boom 23, the undulation angle φ, and the turning angle θ so as to be. The front rated load W _f-lim may be stored in a table format, or may be stored as a function with the length L of the boom 23, the undulation angle φ, and the turning angle θ as variables.

_{As shown in FIG. 7, first, the forward stability monitoring unit 51 has measured values L d} , φ _d , θ _d , from the length measuring device 42, the undulation angle measuring device 43, the turning angle measuring device 44, and the load measuring device 45. Acquire W _d (step S21).

Next, the forward stability monitoring unit 51 confirms that the boom 23 is arranged in the front region of the loaded truck crane CR (step S22). If the boom 23 is not located in the front region, the process ends. On the other hand, when the boom 23 is arranged in the front region, the process is continued.

Next, the forward stability monitoring unit 51 determines the forward rated load W _f-lim (L _d , φ _d , θ) _{corresponding to the measured values L d} , φ _d , and θ _d of the boom 23 length, undulation angle, and turning angle. _d ) is acquired (step S23). Then, the front stability monitoring unit 51 _{compares the measured value W d} of the load with the front rated load W _f-lim (L _d , φ _d , θ _d ) (step S24). Then, when the load W _d exceeds the front rated load W _f-lim (L _d , φ _d , θ _d ), it is determined that the load is overloaded (step S25).

Even if forward stability monitoring is performed by such processing, the work range when the boom 23 is directed diagonally forward can be expanded.

The disclosures of the specifications, drawings, and abstracts contained in the Japanese application of Japanese Patent Application No. 2019-196631 filed on October 29, 2019 are all incorporated herein by reference.

(Additional note)
The following overload prevention device can also be implemented as a reference example of the present invention.

(Reference example 1)
The overload prevention device according to Reference Example 1 is an overload prevention device for a mobile crane having a boom, and has a measured value of a suspended load and a measured value of a boom length, an undulation angle, and a turning angle. May be entered.
Further, the overload prevention device may store the front rated load determined for each boom length and undulation angle so as to be the load of the suspended load when the front rated moment acts on the boom.
Further, the overload prevention device obtains the forward ratio, which is the ratio of the magnitude of the forward overturning component of the overturning moment to the magnitude of the overturning moment acting on the boom, from the measured value of the turning angle, and the forward ratio to the measured value of the load. The front load is obtained by multiplying by, and when the front load exceeds the front rated load corresponding to the measured values of the boom length and the undulation angle, it may be determined as an overload.

(Reference example 2)
The overload prevention device according to Reference Example 2 is an overload prevention device for a mobile crane having a boom, and has a measured value of a suspended load and a measured value of a boom length, an undulation angle, and a turning angle. May be entered.
Further, the overload prevention device may store the forward rated load determined for each boom length, undulation angle and turning angle so as to be the load of the suspended load when the forward rated moment acts on the boom.
Further, the overload prevention device may determine that the load is overloaded when the measured value of the load exceeds the front rated load corresponding to the measured values of the boom length, the undulation angle and the turning angle.

The present invention is applicable not only to loaded truck cranes but also to various mobile cranes.

CR Loading type truck crane 10 General-purpose truck 11 Driver's cab 12 Loading platform 13 Vehicle frame 14 Engine 20 Small crane 21 Base 22 Post 23 Boom 25 Out trigger jack 26 Operating lever group 30 Hydraulic circuit 31 Hydraulic valve unit 32 Tank 33 Hydraulic pump 34 Main oil passage 35 Return oil passage 36a Boom expansion / contraction hydraulic cylinder (hydraulic actuator)
36b winch hydraulic motor (hydraulic actuator)
36c Boom undulating hydraulic cylinder (hydraulic actuator)
36d Hydraulic motor for turning (hydraulic actuator)
36e, 36f Hydraulic cylinder for outriggers (hydraulic actuator)
37a Expansion / contraction switching control valve 37b Winch switching control valve 37c Undulation switching control valve 37d Swing switching control valve 37e, 37f Outrigger switching control valve 38a, 38b, 38c, 38d, 38e, 38f Pilot cylinder 40 Control device 41 Remote Operation terminal 42 Length measuring device 43 Undulating angle measuring device 44 Turning angle measuring device 45 Load measuring device 46 Ground reaction force measuring device AA Overload prevention device 51 Front stability monitoring unit 52 Side stability monitoring unit 53 Strength limit monitoring unit 54 Final Judgment unit

Claims (8)

1. An overload prevention device that has a boom and is built into a crane that transports suspended loads.
   A storage unit that stores a first threshold value set as an upper limit of the load that prevents the crane from tipping forward,
   When the forward load that generates the forward moment acting on the boom is larger than the first threshold value, overload prevention control including at least one of control of stopping the operation of the boom and control of issuing an alarm is performed. An overload prevention device that includes a control unit.
2. The storage unit stores the first threshold value in association with the length and undulation angle that the boom can take.
   The control unit acquires the first threshold value corresponding to the length and undulation angle of the boom from the storage unit, and when the forward load is larger than the acquired first threshold value, the overload prevention control The overload prevention device according to claim 1, wherein the overload prevention device according to claim 1 is carried out.
3. The control unit stores the first threshold value in association with the length, undulation angle, and turning angle that the boom can take.
   The control unit acquires the first threshold value corresponding to the boom length, undulation angle, and turning angle from the storage unit, and when the load of the suspended load is larger than the acquired first threshold value. The overload prevention device according to claim 1, wherein the overload prevention control is performed.
4. The control unit calculates the ratio of the front moment to the overturning moment acting on the boom, calculates the front load by multiplying the load of the suspended load by the ratio, and the front load is the first threshold value. The overload prevention device according to claim 1 or 2, wherein the overload prevention control is performed when the above amount is exceeded.
5. The control unit implements the overload prevention control based on the ground contact reaction force acting on the outriggers of the crane and the lateral threshold value set as the threshold value of the ground contact reaction force that prevents the crane from tipping sideways. , The overload prevention device according to any one of claims 1 to 4.
6. The storage unit stores the strength rated load in advance in association with the posture conditions that the boom can take.
   The overload prevention device according to claim 5, wherein the control unit executes the overload prevention control based on the strength rated load corresponding to the posture of the boom acquired from the storage unit and the load. ..
7. An overload prevention device that has a boom and is built into a crane that transports suspended loads.
   A first determination unit that determines whether or not the crane is in a forward overload state based on a forward load that generates a forward moment among the overturning moments acting on the boom.
   A second determination unit that determines whether or not the crane is in a lateral overload state, and
   A third determination unit that determines whether the crane is in an overloaded state with respect to strength, and
   A control and an alarm for stopping the operation of the boom when the determination result of at least one of the first determination unit, the second determination unit, and the third determination unit is in an overload state. A control unit that implements overload prevention control including control of at least one of the controls that emits
   Overload prevention device.
8. The second determination unit determines whether or not the crane is in a lateral overload state based on the ground contact reaction force acting on the outriggers of the crane.
   The overload prevention device according to claim 7, wherein the third determination unit determines whether or not the crane is in an overload state with respect to strength based on the overturning moment.

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