JPS62174618A - Load detecting device for wining device - Google Patents

Abstract

PURPOSE:To detect a real suspension load even during an acceleration period by finding a value corresponding to the degree of variation in the moving speed of a rope for suspending the load and a value corresponding to the load placed on the rope and performing arithmetic operation based upon a specific expres sion. CONSTITUTION:When the load 1 placed on a floor is suspended through the operation of the winding device, a flywheel 21 rotates and a torque detector 22 detects torque T. Further, a load detector 10 detects the suspension load P placed on the rope 3. Then, an arithmetic means 31 calculates an equation W=P(1/(1+K'T)) and outputs a signal W corresponding to the real suspension load after inertial force due to acceleration is removed. In the equation, K' is a coefficient. Then, a comparing means 32 outputs a signal which commands the operation of the winding device when the signal W is larger then a rated value. Consequently, the operation of the winding device is stopped automatically or manually. Therefore, when the operation for lifting is only started, the real suspension load is found immediately and when the load is larger than a rated load, the operation is stopped immediately, thereby preventing an accident from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a load detection device for a hoisting device such as a crane, and more particularly to an overload detection device.

[Prior art]

Cranes are equipped with an overload detection device to detect whether or not the load being lifted is overloaded, in order to prevent damage to the crane and the like, and to prevent the crane from overturning. I'm trying to stop it.

This overload detection device directly or indirectly detects the force applied to the rope suspending the load, and determines that there is an overload if the force is greater than a set value.

The operation of the hoisting device that produces one rope is stopped automatically by the output of an overload detection device, or manually by a notification from an alarm buzzer or the like.

The following overload detection devices are available.

The device shown in Japanese Patent Publication No. 58-51878 is one in which a rope is elastically supported by pulling it in the radial direction with a clamp, a limit switch is installed on this support, and overload is detected by the operation of the limit switch. It is.

In addition, there is also a method in which a sheave supporting the rope is attached to a strain meter, and the output of the strain meter is input to a comparison circuit to detect whether or not there is an overload.

Moreover, what is shown in Japanese Patent Application Laid-open No. 59-125597 is
A current detector is installed on the motor of the hoisting device, and overload is detected based on the current value.

[Problem that the invention seeks to solve]

In FIG. 2, (a) shows the state of change in the lifting speed of the load after the lifting of the load that has landed is started. (b) shows the state of change in the detected value of the strain meter of the overload detection device at the same time as (a).

As you will see, the load begins to rise at a predetermined acceleration, and after one hour it reaches a constant speed. Therefore, during the period t when acceleration is being performed, an inertial force due to the acceleration is applied to the rope, and the detected value B of the strain meter is larger than the detected value A corresponding to the true weight of the load. The inertial force due to this acceleration is proportional to the acceleration.

In addition, since the hoisting device can lift a load of about 160% of the rated load, it is possible to easily lift a load with the rated load.

Therefore, the true hanging load cannot be detected during one period when acceleration is being performed. This is well known.

Therefore, conventionally, detection is performed as follows.

The first method is to install a timer, detect the load t2 hours after the start of lifting, that is, after the speed becomes constant, and determine the true load ff1A.

However, in general, El is several seconds and the lifting speed is 1
Since the load is approximately 0.00 m/win, the lifting load A is detected when the load is lifted several meters.

Therefore, when a load exceeding a set value (rated value) is actually lifted, it is not possible to detect the overload in advance. For this reason, it was extremely dangerous.

Further, a reference value for determining whether an overload is detected by the overload detection device is set sufficiently larger than the rated load so that the overload detection device does not detect an overload during the acceleration period.

The problem in this case is that even if the load is larger than the rated load, the overload detection device will not operate if the load is lifted at low acceleration.

Furthermore, when a lifted load is being lowered and the lowering speed is reduced, inertial force is added and a similar problem occurs.

As described above, the conventional overload detection device cannot substantially detect overload.

An object of the present invention is to make it possible to detect the true suspended load even during an acceleration period or the like.

Means for Solving Problem C] The above purpose is to obtain a first value T corresponding to the degree of change in speed of movement of a rope for hoisting a load (for example, acceleration α), and a first value T corresponding to the load applied to the rope. This is achieved by calculating the second value P and calculating the following equation.

Here, K' is a coefficient and W is a true load.

[For production]

Find the value T corresponding to the degree of variation in the speed of rope movement (acceleration α or deceleration), and calculate the value P applied to the rope at this value T.
Since this is corrected, it is possible to detect the value excluding the inertial force due to acceleration or deceleration, that is, the true lifting load W.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. A hoisting rope 3 on which a load 1 is suspended via a hanging device 2 passes through guide sheaves 4 and 5 and is wound onto a drum 6 of a hoisting device. The drum 5 is rotated by a motor 8 via a speed reducer 7. The guide sheave 5 is suspended from the main body of the crane via a load detector 10. The load detector 10 suspends the shaft of the guide sheave 5 via an arm 11.

This load detector 10 is a strain meter and outputs an electrical signal proportional to the load applied to the guide sheave. The above configuration is publicly known.

The shaft on the input side of the reducer 7 protrudes to the outside.

A flywheel 21 is connected to this shaft.

A known torque detector 22 for detecting the axial torque of the shaft of the flywheel 21 is installed.

Torque detector 22 outputs an electrical signal proportional to shaft torque.

Reference numeral 30 denotes a control device, which includes a calculation means 31 and a comparison means 32. The calculation means 31 inputs the detected value P of the load detector 1O and the detected number T of the torque detector 22, and performs a process described later (8).
) is calculated.

That is, the calculation means 31 outputs an electrical signal W corresponding to the true hanging load excluding the inertial force due to acceleration.

The comparison means 32 determines that the output W of the calculation means 31 is the rated value (i.e.
It compares whether the load is above the rated value or not, and outputs a signal S instructing to stop the operation if it is above the rated value.

In this configuration, when the hoisting device is operated to lift the load 1 placed on the floor, the load 1 is lifted at an acceleration α.

Also, the flywheel 21 rotates, and the torque detector 22
Torque can be detected with Further, the load detector 10 can detect the hanging load applied to the rope 3. Therefore, the calculating means 31 calculates the equation (8) described later and outputs a signal W corresponding to the true hanging load excluding the inertial force due to acceleration. When the signal W is larger than the rated value, the comparison means 32 outputs a signal S instructing to stop the operation. This automatically
Alternatively, the operation of the hoisting device can be stopped by other means.

Now, lift load 1 with acceleration α? The load iP that acts on the rope 2 while the rope is being moved is expressed by equation (1).

P = W + □ α = w (1 + -) - - - (1) Here, W: Weight of the load 1 to be lifted g: Acceleration of gravity Therefore, the true lifting load W in the above state (i.e. , the weight of load 1 (ff1W) is expressed by equation (2).

On the other hand, the torque T acting on the shaft of the flywheel 21 is expressed by equation (2), where the secondary moment of rotation of the flywheel 21 is {circle around (2)}, and the angular acceleration of the shaft is δ.

T=Iδ −−−−−−−−−−−(3) Since the shaft of the flywheel 21 and the load l are connected to the reducer 7 via the rope 3, the relationship between the acceleration α and the angular acceleration δ is is (4)
It is shown by the formula.

α≦ni −−−−−−, :−−−−−(4) Here,
K is a coefficient determined from the reduction ratio i between the axis of the flywheel 21 of the reducer 7 and the axis of the drum 6 and the diameter of the drum 6.

Using equations (2), (3), and (4), the true hanging load W is expressed as equation (5).

If the reduction ratio between the axis of the flywheel 21 of the reducer 7 and the axis of the drum 6 is i, and the diameter of the drum 6 is D, then the angular acceleration of the axis of the flywheel 21 and the acceleration α of the load 1 are The relationship is shown by equation (6).

・=J♀−−−−−−−−−− (6) Here, π is pi.

Therefore, K in equation (4) becomes equation (7).

πD K=, −−−−−−−−(7) By substituting this into equation (5) and transforming it, equation (8) is obtained.

K' is πD/I@i·g, which is a coefficient determined in advance by the flywheel 21, reducer 7, and drum 6. Therefore, by calculating equation (6) from the detection value P of the load detector 10 and the detection value T of the torque detector 22, the true hanging load W can be obtained.

Therefore, once the lifting operation is started, the true lifting load can be determined immediately, and if the rated load is exceeded, the operation can be stopped immediately, thereby preventing accidents.

Further, in a case such as a container crane that lifts a container fixed to a ship, the detected torque value is zero, so overload can be detected.

If the hoisted load is decelerated while being lowered, the detected value P of the load detector 10 will increase due to the inertial force caused by the deceleration. However, the detected value T of the torque detector' 22
Since the value T is no longer zero, the signal S instructing to stop the operation is not outputted. In this case, the detected value T is negative, so it is necessary to set it as an absolute value, for example.

In the embodiment described above, the flywheel 21 and the torque detector 22 that detects the shaft torque of the flywheel 21 are used as means for calculating the magnitude of inertial force due to acceleration.

Therefore, as shown in FIG. 2C, only the shaft torque due to acceleration can be detected, that is, torque is output only during the acceleration period. The detected value is proportional to the acceleration. Therefore, the inertial force due to acceleration can be detected accurately. Moreover, since its output is relatively stable, it can be detected accurately.

Note that in reality, there will be fluctuations in the detected values, and it may be necessary to install a filter or the like.

Further, since the flywheel 21 is installed on the input shaft side of the speed reducer 7, the number of revolutions is high and can be detected accurately.

In the above embodiment, only one rope 3 is used from the load 1 to the drum 6. The number of ropes, the way the ropes are hung, etc., and the relationship between the position and number of load detectors 10 and the detected value of the load detector 10 are well known, so they are omitted in the above example, and in reality, the above The detected value P is corrected based on a known relationship.

Further, although the output of the load detector 10 includes the weight of the hanging tool 2, etc., this is ignored in the above description.

The flywheel 21 may be rotated by a guide sheave, for example.

When the flywheel type torque detection device 20 is not used, the following can be done. The shaft of a pulse transmitter that outputs pulses by rotating the shaft is connected to, for example, a guide sheave, and pulses are transmitted by rotating the guide sheave 4. The calculating means 31 calculates the acceleration α or deceleration α of the movement of the rope 3 based on the pulse interval, and calculates the true hanging load by calculating the equation (2). If α is T and 1/g is , then equations (2) and (8) are the same.

A DC motor is used as the motor 8, and the load applied to the rope 3 can be calculated from its current value. However, in this case, it is necessary to add the unique characteristics of the DC motor to the calculation.

〔Effect of the invention〕

As described above, according to the present invention, when the speed of movement of the load fluctuates, for example, even after lifting of the load has started, the detected value of the lifted load can be corrected based on the degree of fluctuation in the speed, for example, acceleration. Therefore, the true lifting load can be determined. When used as an overload movement detection device, it is possible to determine whether or not there is an overload after the start of lifting, and if there is an overload, the operation can be immediately stopped, thereby preventing accidents.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a load detection device according to an embodiment of the present invention, and Fig. 2 is a diagram showing the relationship between the load lifting speed, the detected load value, and the detected torque value after the start of lifting the load. be. i, ----11 load, 3-111 rope, 4.5---
--Guide sheave, e -----Drum, ? ------
-Reducer, 8-----Motor, 21-----Flywheel, 22----, -) Lux detector, 31-----
-1 calculation means, 1st dimension, 2nd figure

Claims (1)

[Claims] 1. A first detector that detects a first value T that corresponds to the degree of variation in the moving speed of a rope that lifts a load, and a second value that corresponds to the load applied to the rope. a second detector for detecting P; a calculation means for inputting the first value T and the second value P and performing the following calculation to obtain the true load W; (1
+K'T)] Here, K' is a coefficient. A load detection device for a hoisting device consisting of: 2. The load detection device for a hoisting device according to claim 1, wherein the first detector is provided to detect the degree of fluctuation in the moving speed of the rope itself. 3. In claim 1, the first detector is a flywheel rotated by a hoisting device that moves the rope or a rotating body that rotates due to the movement of the rope, and a torque detector that detects the shaft torque of the flywheel. A load detection device for a hoisting device.