JPH06345240A - Belt conveyor slip detection and slip prevention method - Google Patents

Abstract

(57) [Abstract] [Objective] The present invention reduces the detector maintenance cost by detecting the slip of the belt conveyor from the on-site detection to the current detection in the electric room, and further, the slip is controlled by speed control when the slip occurs. Providing a reduction in production by stopping the line. [Configuration] By inputting the load current of the belt conveyor drive motor into a personal computer and analyzing the current change,
By detecting the phenomenon that the load current suddenly drops and suddenly rises when the belt conveyor slips, and the repetitive amplitude becomes large, the slip is detected when it is the same as the specific slip pattern programmed in the personal computer. At the same time as the slip detection, the AC variable speed control device reduces the rotational speed of the drive motor in steps to prevent the slip.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt slip detecting method and a slip preventing method under all conditions of a belt conveyor for transporting raw materials in the steel industry.

[0002]

2. Description of the Related Art In a conventional belt slip detecting method, a striker and a proximity limit switch are attached to a driven pulley portion of a belt conveyor, and a pulse signal of the limit switch is input to a motion controller in an electric room. This is a detection method that detects the number of rotations of the pulley and issues a belt slip alarm when the decrease in the number of pulses is detected by the motion controller. There is a pulley rotation speed setting in the motion controller, and when the rotation speed of the pulley falls below the set value when the drive motor operation signal is input, it is detected as a slip. The slip detection signal from the motion controller stops the motor through the relay circuit and issues an alarm at the same time.

In the prior art, Japanese Patent Laid-Open No. 61-45819 has been used.
In the method of detecting an abnormality in a transportation system using a conveyor in Japanese Patent Publication, there is a method of detecting an abnormality by comparing a load current management value and an actual current value with respect to an actual carry amount from a relationship between a load current and a carry amount of a motor during normal operation. is there.

[0004]

In the conventional method, the distance from the limit switch mounted in the vicinity of the belt conveyor to the electric room is as long as 2 km at the maximum, so it is necessary to prevent noise. Further, since a limit switch and a motion controller are required in pairs for one belt conveyor, it is necessary to lay a long cable when adding a slip detector. Further, since the detector is mounted in the vicinity of the belt conveyor, the fall of the conveyed product may cause damage to the detector, disconnection of the cable, or malfunction due to noise, resulting in production interruption due to line suspension. Furthermore, if slippage cannot be detected when the slip occurs, the transported material accumulates on the belt, which requires a large reduction in production due to a belt cutting accident and a large amount of restoration and maintenance costs.

Recently, it has become necessary to attach slip detectors to all belt conveyors due to belt breakage accidents due to the accumulation of conveyed products and belt fires due to slippage. It is necessary to lay a long cable, which requires a large construction cost. In addition, there is a detector near the rotating body, which entails the risk of being caught during inspection work, and it is necessary to periodically replace and maintain the detector and cable due to deterioration due to the outdoor environment. Further, the conventional method is a method of stopping the belt by slip detection, and in rainy weather, slip is detected even in the case of a little rain and the production is forced to be stopped by stopping the line.

A conventional technique, Japanese Patent Laid-Open No. 61-45819.
Since the gazette is a comparison with the current under normal conditions, the slip cannot be specified. Further, slip detection cannot be performed only by detecting and stopping.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves all of the above-mentioned drawbacks, and catches a phenomenon in which a sudden drop and a sudden increase in load current, which occur when a belt conveyor slips, becomes a pair, and It is a method of detecting a slip when the slip pattern is the same as the programmed slip pattern.

As a result of various studies and experiments on the belt slip phenomenon, the present inventors have discovered a phenomenon in which the load current of the drive motor of the belt conveyor changes in a certain manner. FIG. 1 is a graph of load current. As shown in the figure, this phenomenon gradually rises when a slip occurs, but at the same time as the slip occurs, it becomes idle and the current suddenly drops. After that, the load is applied again and the speed rises sharply. When this phenomenon occurs, by programming the personal computer to detect slip, slip detection can be performed without detecting the rotation of the pulley as in the conventional case.

Simultaneously with slip detection, the AC variable speed control device reduces the rotational speed of the drive motor in steps to prevent slip. FIG. 2 shows an outline of the hardware configuration. The motor load current is input to the personal computer, and the VVVF speed control device controls the motor speed by the output signal of the personal computer.

[0010]

EXAMPLE FIG. 3 shows an example in which, at the same time when a phenomenon in which the load current suddenly drops and suddenly rises in pairs, the rotational speed is reduced by VVVF to prevent slippage. The load current gradually rises from normal current of 57A to 70A, and when it becomes idling, it suddenly drops to 62A. Then, the load is applied again, it rapidly rises to 72A, and it drops to 58A again.
Soar to 4A. When this pattern occurs, slip is detected, and after one second, the motor rotation speed is controlled from 980 rpm to 970 rpm, which is a 10% reduction. After that, when the load current deviates from the slip pattern, the original rotation is restored after 5 seconds.

In order to specify the slip pattern, the cross point with the current smoothed by the CR circuit having a certain time constant is measured, the time Δt between the cross points and the current Δi are obtained, and Δi / When Δt becomes a certain value or more and becomes large, it is determined to be slip.

[0012]

[Function] The function of the pattern analyzed by the personal computer is that the relative fluctuation of the current value with respect to the reference is larger than a certain fixed value, the signal of the relative fluctuation is opposite, and the relative fluctuation increases, which is repeated a specified number of times or more. It is judged that it is a slip.

Next, the flow of slip detection is shown in FIG.

[0014]

According to the present invention, all the drawbacks of the conventional method are eliminated, and the following effects are obtained. No on-site detector is required, and troubles such as noise, detector damage, and cable disconnection can be prevented. In addition, the safety of inspection work can be improved and periodic maintenance costs can be reduced. The reliability is improved, and it is possible to prevent the belt cutting accident due to the undelivered load accumulation. When adding a slip detector, it is not necessary to lay a long cable, and construction costs can be greatly reduced. By controlling the motor speed when slippage occurs, slippage can be prevented, line downs can be reduced, and raw material transportation can be stabilized.

[Brief description of drawings]

FIG. 1 is a graph showing a motor load current when a slip occurs.

FIG. 2 is a schematic diagram of a hardware configuration of a circuit that detects a slip by detecting a change in a motor load current and prevents the slip.

[Fig. 3] The motor speed is controlled when slip is detected,
It is a figure which shows the Example which prevented the slip.

FIG. 4 is a flow diagram of a slip detection method according to the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hiromitsu Yamaguchi 1 Kimitsu, Kimitsu City, Chiba Shin Nippon Steel Co., Ltd. Kimitsu Steel Co., Ltd.

Claims (2)

[Claims] Claims: 1. A phenomenon in which a load current of a drive motor is paired with a sudden drop and a rapid rise, which occur when a belt conveyor slips, and a repetitive amplitude becomes large, and a specific pattern is analyzed. A belt conveyor slip detection method, characterized in that the belt slip is detected by. 2. When the load current of the belt conveyor drive motor suddenly drops and rises in pairs, the AC variable speed control controls the speed of the motor to prevent the belt conveyor from slipping. Belt conveyor slip prevention method.