JPH01139497A - Method and device for controlling bucket of crane with rope type bucket - Google Patents

Abstract

PURPOSE: To maximize grabbing efficiency by adjusting the voltage and frequency of a support motor to an optimal value according to the drop of a bucket when load grabbing work is performed by a bucket. CONSTITUTION: When a bucket 1 grabs load, in the condition that the bucket 1 is completely opened by an opening/closing motor M2 using an opening/closing inverter 12 consisting of a rectifying circuit 121 and an inverting circuit 122, it is lifted down by a winding motor M1 via a support inverter 11 and reached a floor. Next, when drop grabbing action is performed, because torque of the support motor M1 is set to a minimum weak torque required to remove sag of a support rope R1, a rectifying circuit 111 of the support inverter 11 adjusts voltage and an inverting circuit 112 adjusts frequency to an optimal value, the bucket 1 is wound down at slight speed and simultaneously is closed by the opening/closing motor M2, and load is covered. Thus, grabbing efficiency of the bucket can be maximized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for controlling a bucket in a rope-type bucket crane.

[Conventional technology]

In conventional rope-type cranes with buckets, the lifting and lowering of the bucket (support) and the opening and closing of the bucket are operated using ropes. It is operated by an electric hoisting drum for support and an electric hoisting drum for opening and closing, respectively, located above.

Conventionally, the supporting electric drum and the opening/closing electric drum are each operated by separate electric motors, and are operated by secondary resistance control or dynamic braking of a wound induction motor by a direct control device or an indirect control device by an operation controller. Ta.

When a bucket is used to grab a load, the bucket sinks as it grabs the load, so it is necessary to loosen the brake on the electric motor for supporting the bucket so that the bucket can sink.

However, if the brake is loosened, the supporting motor becomes free and rotates more than necessary, causing the supporting rope to become more slack than necessary, causing problems when the bucket is next hoisted.

For this reason, conventionally, a secondary resistor was added to the secondary side of the wound induction motor used as the support motor to generate a weak torque in the hoisting direction in the support motor and prevent the support rope from sagging. There is a way to do it.

However, in this method, the motor must be a wound induction motor, and a secondary resistor and a secondary resistor shorting device are required, so there is a problem that maintenance and inspection are time-consuming.

Furthermore, if the torque generated by the supporting motor becomes stronger than necessary, the bucket will be hoisted up and down, making it impossible to efficiently grip the load with the bucket.

There was also the problem that this generated torque could not be easily adjusted using conventional methods.

For this purpose, variable voltage/variable frequency inverters 11 and 12 are provided between the primary sides of the supporting motors and opening/closing motors and the power supply, as shown in FIG. Perform speed control,
A method has been proposed in which the load is grabbed using a bucket. The circuits shown in FIG. 6 are used for the inverter devices 11 and 12, and each forward conversion circuit 111.1
21 and inverse conversion circuits 112 and 122.

With this method, the speed of each motor can be controlled, but when the bucket sinks, the support motor moves down, or rotates in the opposite direction, and the torque generated by the support motor decreases. There was a problem in that upward torque could not be generated and slack in the support rope could not be completely prevented.

[Problem that the invention seeks to solve]

The present invention provides a bucket gripping control method and device that can reliably prevent the support rope from slackening in a simple manner and efficiently grip the load when the bucket is used to grip the load. The purpose is to provide.

[Means for solving problems]

The present invention provides a variable voltage/variable frequency inverter device on the primary side of the hoisting/up/down (support) motor and the opening/closing motor of a rope-type bucket-equipped crane, controls the speed of each motor, and allows the bucket to grasp loads. In the control device that performs
The present invention is characterized in that a thyristor primary voltage control circuit is provided in the forward conversion section of the inverter device for the hoisting/uploading (support) motor to prevent the support rope from slacking during the work of grasping the load in the bucket.

〔Example〕

In a crane with a rope type bucket, the operation (movement) procedure of the bucket for efficiently grasping a load with the bucket will be explained based on the schematic configuration and operation diagram of the bucket section shown in FIG. 3.

The hoisting (support) electric motor M1 is connected to the hoisting drum 2 via a reduction gear (not shown). A bucket winding/up/down rope R1 is wound around the hoisting drum 2, and the tip of the rope R1 is hooked to a part of the bucket 1.

Further, the opening/closing electric motor M2 is connected to the opening/closing drum 3 via a reduction gear (not shown). A bucket opening/closing rope R2 is wound around the opening/closing drum 3, and the tip of the rope R2 is hooked to a part of the bucket 1.

To grasp a load with a bucket, first, as shown in Figure 3 (A), with the bucket 1 fully open, the hoisting (support) motor M1 lowers the bucket 1 and lands it on top of the load. Next, as shown in FIG. 3(B), the bucket 1 is closed by the opening/closing electric motor M2, and the front part is gripped. At this time,
In order to efficiently grasp the load, the hoisting (support) motor M
It is necessary to lower the bucket 1 at a slow speed by controlling the bucket 1 at a low speed.

This action of lowering the bucket at a very slow speed and grasping the load while closing the bucket is hereinafter referred to as "sinking grasp."

This sinking and grasping motion is essential for efficiently grasping the load.

When the load grasping work is completed, the bucket 1 is hoisted up as shown in FIG. 3(C). When the hoisting of bucket 1 is completed,
Traverse and travel movements move the crane into position to release the load. Next, the operations shown in FIGS. 3(D) and 3(E) are performed to release the load to a predetermined position. When the discharge of the load is completed, the bucket is hoisted up. By reversing the above operations, it is possible to transport loads using buckets.

In order to reliably perform the sinking and grabbing operation, the bucket is closed while sinking, so the rope R1 that supports the bucket must not slack during this time, that is, the support rope R1 must be kept under an appropriate tension at all times. It is necessary to reel in tension.

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows the configuration of a bucket control device for a rope type bucket crane according to the present invention.

In Figure 1, Ml is the supporting motor that hoists and raises (supports) the bucket, and B is the brake for the supporting motor.
1. The opening/closing electric motor that opens and closes the bucket is denoted by M2, the brake for the opening/closing electric motor is denoted by B2, and each electric motor M1
, M2 are connected to a support inverter 11 and an opening/closing inverter 12, respectively.

The support inverter 11 is composed of a forward conversion circuit 111 and an inverse conversion circuit 112, and the forward conversion circuit 111 includes a thyristor 11 that can vary the magnitude of the voltage supplied to the support motor M1.
A thyristor primary voltage control section 11V that can be controlled by a circuit consisting of 8 or the like is provided. Further, the inverse converter 112 variably controls the frequency supplied to the support motor M1. Note that the magnitude and frequency of the supplied voltage can be independently controlled.

The switching inverter 12 includes a forward conversion circuit 121 and an inverse conversion circuit 122.

The operation of lowering the bucket 1 and grabbing a load with the bucket 1 will be explained based on the torque-speed curve of the supporting motor M1 shown in FIG. 2.

In Figure 2, when T is used to grab a load with bucket 1, bucket 1 sinks as it is grabbed, but at this time, support rope R
Indicates the torque in the hoisting direction required to prevent the sagging of 1.

A characteristic curve C shown by a dotted line shows a torque-speed curve when hoisting is carried out at full speed without controlling the voltage and frequency supplied to the support motor M1.

The torque-speed curve of the support motor M+ can be changed as shown in FIG. As shown, for example, the generated torque can be controlled within a minute range as shown by characteristic curves A and B.

Therefore, by setting the torque of the supporting electric motor M1 to the minimum weak torque necessary to take up the slack of the supporting rope R1 when grasping the bucket, the bucket 1 can be supported while the supporting rope R7 is always kept under tension. Grasping efficiency (grabbing amount) can be maximized.

FIG. 4 is a drawing showing the circuit configuration of the control device for the support motor M1 of the present invention.

The forward conversion circuit 111 is composed of a thyristor 118, etc., each gate 118G of each thyristor IIS is connected to each terminal T1 to T6 of a thyristor gate control circuit GC, and the firing angle of the thyristor is controlled by the thyristor gate control circuit GC. The motor is designed to control the magnitude of the voltage supplied to the support motor M1.

The input terminal of the thyristor gate control circuit GC is connected to a contact point for a weak torque command signal S and a variable resistor VR for voltage setting. It is designed to operate when the slack of the support rope R+ is not prevented during the sinking and grasping operation in step 1, and the weak torque that prevents the slack of the support rope R1 set by the operation of this weak torque command signal S is generated. The phase of each thyristor IIS is controlled so that the voltage becomes the same.

Further, the voltage setting variable resistor VR converts the signal voltage input to the thyristor gate control circuit GC into the weak torque command signal S.
During operation, the signal voltage is set so that the preset optimum weak torque is achieved.

The inverse conversion circuit 112 is composed of transistors IIT and the like, and controls the frequency supplied to the support motor M1 by controlling the on/off of each transistor IIT.

Therefore, the magnitude and frequency of the voltage supplied to the support motor M+ can be independently controlled.

Therefore, the torque generated by the support electric motor M1 can be set to the optimal weak torque in the hoisting direction necessary to take up the slack of the support rope R1 during sinking and grasping.

As described above, in the present invention, the frequency and voltage for supplying torque control of the support motor M1 during sinking and grasping can be individually adjusted.

Therefore, the inverse conversion circuit 111 has voltage (■), seven frequencies (
In F) control, voltage (■), frequency (F) constant control is performed, and the voltage (V) is lowered by the forward conversion circuit 122. In other words, the inverse conversion circuit 111 is a voltage (V)
7. A constant frequency (F) control is performed, and a forward conversion circuit 122 performs control to lower the voltage (V) as necessary.

Therefore, in order to perform the sinking operation, bucket 1 is sunk while bucket 1 is closed and the load is grabbed. At this time, the support rope R+ that supports bucket 1 should not be slack, and an appropriate tension should be applied to support rope R1. Since the bucket 1 can be sunk, the load can be efficiently grabbed by the bucket 1.

Note that the induction motor used in the present invention is not limited to squirrel-cage induction motors, but can also be used by short-circuiting the secondary side of a wound wire induction motor to achieve control similar to that of a squirrel-cage induction motor. Of course.

〔Effect of the invention〕

The present invention has a simple configuration and can take up the slack in the support rope by adjusting the voltage and frequency of the support motor to optimal values in accordance with the sinking of the bucket when a bucket is used to grab a load. Since the bucket can be supported by generating the necessary weak torque in the hoisting direction and applying appropriate tension to the support rope without giving it slack, it has the effect of maximizing the efficiency of grasping the load in the bucket.

[Brief explanation of the drawing]

Fig. 1 is an embodiment diagram showing the bucket control device of the present invention, Fig. 2 is a torque-speed curve diagram, Fig. 3 is an explanatory diagram of bucket operation, Fig. 4 is a circuit diagram of the control device, and Fig. 5 is An embodiment of a conventional bucket control device, FIG. 6 is a circuit diagram thereof. Ml is the hoisting motor, M2 is the opening/closing motor, R+ is the hoisting/lowering rope, R2 is the opening/closing rope, 1 is the bucket, 2
1 is a hoisting drum, 3 is an opening/closing drum, 11 is a support inverter, 12 is an opening/closing inverter, 111, 11
2 is a forward conversion circuit. U) Trowel

Claims (2)

[Claims] (1) In a crane with a rope bucket, the speed of each motor is controlled by a variable voltage/variable frequency inverter device installed on the primary side of the hoisting/lowering (support) motor and the opening/closing motor, and the bucket is used to pick up loads. When the bucket is lowered and landed on the ground, the electric motor for hoisting and lowering (support) generates a weak torque in the hoisting direction to eliminate slack in the support rope, and then lowers the support rope at a very slow speed while hoisting the opening/closing rope. A bucket control method for a crane with a rope type bucket, characterized in that the bucket is allowed to sink at a slow speed and then closed to perform a load grasping operation. (2) A variable voltage/variable frequency inverter device is installed on the primary side of the hoisting/uploading (support) motor and the opening/closing motor of the rope-type bucket-equipped crane to control the speed of each motor and allow the bucket to pick up loads. A crane with a rope type bucket, characterized in that a thyristor primary voltage control circuit is provided in the forward conversion section of the inverter device for the hoisting/up/down (support) motor in order to prevent the support rope from slackening in the bucket control device for the bucket. Bucket control device.