JP6744230B2 - Control method for crane equipped with hydraulic grab bucket - Google Patents

Description

The present invention relates to a control method for a crane provided with a hydraulic grab bucket, and more particularly to a control method for a crane provided with a hydraulic grab bucket for suppressing a temperature rise of hydraulic oil.

Conventionally, a crane is generally used in which a grab bucket that holds a loose piece is suspended by a wire rope in order to pick up and release the loose piece such as dust, coal, gravel, ore, and the like. ..

By the way, in order to open and close the grab bucket which is hung on a crane of this type, a grab bucket equipped with a hydraulic unit is widely used (for example, refer to Patent Document 1).

This hydraulic unit drives a pump by an electric motor so that a hydraulic cylinder that opens and closes a grab bucket is expanded and contracted, and hydraulic oil discharged from this pump is hydraulically operated through an electromagnetic directional control valve. The hydraulic cylinder is selectively supplied to the cylinder to cause the hydraulic cylinder to expand and contract, whereby the claws of the grab bucket are opened and closed.

By the way, the conventional hydraulic unit mounted on the grab bucket has a problem that the temperature of the hydraulic oil is likely to rise because the flow rate of the hydraulic oil cannot be properly adjusted.
That is, when a fixed displacement pump is driven by a commercial power source, excess hydraulic oil is allowed to escape to an oil tank via a relief valve, but the discharge flow rate of the pump is constant, so heat generation due to pump leakage occurs. In addition to this, the relief valve also generates heat, and the temperature of the hydraulic oil flowing through the hydraulic circuit in the grab bucket rises.

When the amount of heat generated by the hydraulic oil flowing in the hydraulic circuit is greater than the amount of heat released from the grab bucket, the temperature of the hydraulic oil rises. It was necessary to stop the operation of the crane until the temperature of the hydraulic oil dropped.

In order to suppress the amount of heat generated by the hydraulic oil flowing in the hydraulic circuit while maintaining the pressure of the hydraulic oil supplied to the hydraulic cylinder, it is necessary to suppress the oil amount when the hydraulic oil pressure exceeds the required pressure. There is.

As a means of adjusting this oil amount, there is a method of directly adjusting the oil amount when it exceeds the required pressure by detecting the pressure of the hydraulic oil using a variable displacement pump, but the variable displacement pump is fixed. Compared to the capacity pump, the structure of the pump is complicated and expensive, and the pump is consumed frequently due to frequent use, and there is a problem in durability. Therefore, frequent maintenance is required.

In addition, there is also a method of combining the fixed displacement pump and the inverter to make the rotational speed of the fixed displacement pump variable, but incorporating the inverter in the grab bucket is problematic in terms of durability and requires frequent maintenance. There was a need. To address this issue, when the inverter is installed separately from the grab bucket, the electric signal of the pressure detector that detects the pressure of the hydraulic oil is installed separately via the power supply cable to the grab bucket. Since it is necessary to pull it up to the equipment, it is necessary to take measures against noise by increasing the number of cores of the power supply cable and extending the signal line, and there are many problems in terms of quality.

Further, the applicant of the present application previously provided with an electric motor that can be driven in the forward and reverse directions and a reversible variable displacement hydraulic motor that is rotationally driven by this electric motor, and the operating oil discharged from this reversible variable displacement hydraulic motor is the hydraulic oil passage. A hydraulic unit for grab bucket mounting that can keep the flow rate of hydraulic oil properly and suppress the temperature rise of hydraulic oil by supplying it to the hydraulic cylinder that opens and closes the bucket via the (See Patent Document 2).
However, this grab bucket mounting hydraulic unit has a special specification that uses an electric motor that can be driven in the forward and reverse directions and a reversible variable displacement hydraulic motor. It could not be applied and lacked versatility.

JP, 9-194184, A JP, 2005-113847, A

The present invention has been made in view of the problems associated with the temperature rise of hydraulic oil in a crane equipped with the conventional hydraulic grab bucket, and this problem is solved by the number of rotations of an electric motor control device that controls an electric motor drive device disposed on the side of an overhead crane. An object of the present invention is to provide a control method for a crane equipped with a hydraulic grab bucket, which can be eliminated by performing control, and at the same time, can suppress an increase in various costs such as initial, running, and maintenance. ..

To achieve the above object, a control method of a crane provided with a hydraulic grab bucket of the present invention, in order to adjust the discharge flow rate of the pump to drive the hydraulic cylinder for opening and closing operation of the Grab buckets, the grab bucket side The rotation speed of the electric motor is controlled by the electric motor control device based on the electric energy calculation value obtained from the voltage value and the current value of the electric motor drive device installed on the overhead crane side that drives the electric motor that drives the installed pump. A method for controlling a crane equipped with a hydraulic grab bucket that suppresses the amount of heat generated by the hydraulic oil flowing in the hydraulic circuit by performing a grip and hold of the grab bucket so that the calculated electric power value When the frequency command value of the electric motor drive device is decreased at 70 to 90% of the above, the rotational speed of the electric motor is decreased so that the rotational speed of the pump is decreased. By increasing the frequency command value of 1, the rotation speed of the electric motor is increased, and the rotation speed of the pump is increased .

According to the control method for the crane including the hydraulic grab bucket of the present invention, the problem regarding the temperature rise of the hydraulic oil of the crane including the hydraulic grab bucket is caused by the voltage value of the electric motor drive device arranged on the overhead crane side. This can be solved by controlling the rotation speed of the electric motor by the electric motor control device based on the electric power calculation value obtained from the current value, and at the same time, it is possible to suppress an increase in various costs such as initial, running, and maintenance.

An example of an overhead crane equipped with a hydraulic grab bucket for carrying out the control method of a crane equipped with a hydraulic grab bucket of the present invention is shown, (a1) is an operation state diagram of the hydraulic grab bucket in an open state, ( a2) is an operation state diagram of the hydraulic grab bucket in a closed state, and (b) is an explanatory diagram of an operation circuit (hydraulic circuit, drive/control electric circuit) of the hydraulic grab bucket. It is a flowchart which shows one Example of the control method of the crane provided with the hydraulic grab bucket of this invention. It is a time chart corresponding to the flowchart. It is a graph which shows the same characteristic test result.

An embodiment of a control method for a crane equipped with a hydraulic grab bucket according to the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of an overhead crane equipped with a hydraulic grab bucket that implements the method of controlling a crane equipped with a hydraulic grab bucket of the present invention.
The overhead crane 1 equipped with this hydraulic grab bucket, in the same manner as the conventional overhead crane equipped with a hydraulic grab bucket, specifically expands and contracts the hydraulic cylinder 23 that opens and closes the grab bucket 2. The pump 22 is driven by the electric motor 21, and the hydraulic oil discharged from the pump 22 is selectively supplied to the head side or the rod side of the hydraulic cylinder 23 via the electromagnetic directional control valve 24 to expand and contract the hydraulic cylinder 23. By doing so, the opening/closing operation of the claw 20 of the grab bucket 2 is performed.

By the way, generally, in a hydraulic circuit, an object is driven by viscous hydraulic oil flowing in the hydraulic circuit.
On the other hand, it is known that friction occurs due to the flow of hydraulic oil in hydraulic equipment and pipes, and most of the lost energy is converted into heat.
H=α×Q×ΔP
Here, H: calorific value, Q: flow rate, ΔP: pressure loss (ΔP=βQ ₂ ).
=α×Q×βQ ₂
=γ×Q ₃
Here, α, β and γ are coefficients determined by the viscosity of oil and the shape of the pipe.
That is, if the flow rate (Q) is reduced, the heat generation amount (H) is also reduced.

On the other hand, the upper limit of the pressure of the hydraulic oil required to move the grab bucket is set, and the excess hydraulic oil is allowed to escape to the oil tank 26 via the relief valve 25. The increase in the amount of leakage results in an increase in the flow rate of the hydraulic oil flowing in the hydraulic circuit, and the amount of heat generated by the hydraulic oil increases. Further, if the pump 22 is rotated more than necessary, not only the amount of leak inside the pump 22 is increased and heat is generated, but also the load of the electric motor 21 that drives the pump 22 is increased. Here too, heat is generated unnecessarily, leading to a rise in the temperature of the hydraulic oil inside the grab bucket.
From this, it can be seen that it is necessary to properly adjust the flow rate of the hydraulic oil in order to suppress the temperature rise of the hydraulic oil.

By the way, the flow rate Q discharged by the pump can be expressed by the following equation.
Q=N×q
Here, N is the rotation speed of the pump, and q is the capacity of the pump.
When the pump capacity (q) is constant, the required flow rate (Q) can be secured by optimally adjusting the rotation speed (N). From this, the power (W) that can secure the required discharge pressure (P) is monitored from the relationship between the power (W) and the discharge pressure (P) shown in the following formula, and the rotation speed (N) of the pump, that is, By minimizing the number of rotations of the electric motor, it becomes possible to suppress the temperature rise of the hydraulic oil.
W=N×q×P
Here, W is electric power and P is discharge pressure.

Based on this viewpoint, in order to adjust the discharge flow rate of the pump 22 that drives the hydraulic cylinder 23 that opens and closes the glove bucket 2, the electric motor 21 that drives the pump 22 disposed on the glove bucket 2 side is driven. By controlling the rotation speed of the electric motor 21 by the electric motor control device 12 based on the electric energy calculation value obtained from the voltage value and the current value of the electric motor drive device 11 arranged on the side of the overhead crane 1, The amount of heat generated by flowing hydraulic oil is suppressed (hereinafter referred to as "cycle logic control").
Here, the rotation speed control of the electric motor 21 by the electric motor drive device 11 and the electric motor control device 12 is performed by a general frequency control device such as an inverter to make the frequency command value of the electric motor drive device 11 variable, The rotation speed of the electric motor 21 is made variable, and the rotation speed of the pump 22 is made variable.

More specifically, as shown in FIGS. 2 and 3, by holding and holding the dust W by the claws 20 of the grab bucket 2, the calculated value of the electric energy obtained from the voltage value and the current value of the electric motor drive device 11 is the maximum. Before the amount of electric power is reached, specifically, when the calculated amount of electric power is 70 to 90%, preferably 75 to 85%, and more preferably about 80% of the maximum amount of electric power, the electric motor drive device 11 By lowering the frequency command value of (for example, from 50 Hz to 10 Hz), the rotation speed of the electric motor 21 is reduced and the rotation speed of the pump 22 is reduced.
Here, at the start of additional closing of the claw 20 of the grab bucket 2, the electric power calculation value decreases, so by increasing the frequency command value of the electric motor drive device 11, the rotation speed of the electric motor 21 is increased and the pump 22 of the pump 22 is increased. Try to increase the rotation speed.

FIG. 4 shows a result of a characteristic test (a comparison test with a reference value (comparative example) in which cycle logic control is not performed, of a control method of a crane including the hydraulic grab bucket.
As shown in FIG. 4, it was confirmed that by performing the cycle logic control, the temperature rise in the hydraulic unit was small and the power consumption could be reduced (29% reduction).

As described above, according to the control method of the crane including the hydraulic grab bucket, the electric motor drive device 11 and the electric motor control device 12 are provided on the side of the overhead crane 1, and the electric motor 21 and the pump 22 (fixed capacity pump on the side of the grab bucket 2). ) Is separated and arranged, it is possible to realize both economical efficiency and reliability, and at the same time to realize energy saving and suppression of temperature rise of hydraulic oil.

The control method of the crane provided with the hydraulic grab bucket of the present invention has been described above based on the embodiment, but the present invention is not limited to the configuration described in the above embodiment and deviates from the gist thereof. The configuration can be changed as appropriate within the range that does not.

The control method of the crane provided with the hydraulic grab bucket of the present invention solves the problem of the temperature rise of the hydraulic oil, and at the same time, can suppress the increase of various costs such as initial, running, maintenance, etc. It can be suitably used for the purpose of an overhead crane equipped with a hydraulic grab bucket, and can also be used for the purpose of an overhead crane equipped with a new or existing hydraulic grab bucket.

DESCRIPTION OF SYMBOLS 1 Overhead crane 11 Electric motor drive device 12 Electric motor control device 2 Grab bucket 20 Claw 21 Electric motor 22 Pump 23 Hydraulic cylinder 24 Electromagnetic directional control valve 25 Relief valve 26 Oil tank

Claims (1)

To adjust the discharge flow rate of the pump to drive the hydraulic cylinder for opening and closing operation of the Grab buckets, driving the electric motor driving the pump is disposed on the grab bucket side, the electric motor drive which is disposed on the ceiling crane side A hydraulic grab bucket that suppresses the amount of heat generated by the hydraulic oil flowing in the hydraulic circuit by controlling the number of revolutions of the electric motor by the electric motor control device based on the electric energy calculation value obtained from the voltage value and current value of the device A method of controlling a crane, comprising: holding and holding a grab bucket to lower the frequency command value of the electric motor drive device when the electric power calculation value is 70 to 90% of the maximum electric power, thereby rotating the electric motor. Decrease the number of pumps to lower the rotation speed of the pump, and at the start of additional closing of the grab bucket, increase the frequency command value of the motor drive device to increase the rotation speed of the motor and increase the rotation speed of the pump. A method of controlling a crane equipped with a hydraulic grab bucket.

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