JPH0344520A - Detection of abnormality in rotary roller for belt conveyor and vibration sensor therefor - Google Patents

Abstract

PURPOSE:To enable detection of slight abnormality while achieving a higher detection accuracy by comparing vibration levels at a frequency equal to respective resonance frequencies between a frame desired to detect abnormality and a frame during a normal operation. CONSTITUTION:Vibration sensors 13 are mounted on respective frames 15 and output signals of the sensors 13 are switched with a scanner 17 as directed from an arithmetic processor 20. Vibration level at a frequency equal to a resonance frequency which is selected with the scanner 17 and extracted with the sensor 13 are compared with a vibration level at a frequency equal to a resonance frequency during a normal operation measured beforehand by a comparator 18 and judged in three stages -- 'good', 'caution' and 'danger'. Data resulting from the judgment are inputted into a device 20 through a scanner 19 operated as directed from the device 20 together with a number of the sensor 13 to be shown on a display. Thus, abnormality of a rotary roller supported with the frame 15 can be discovered while it is still slight and also, judgment of abnormality is accomplished at a high accuracy.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for detecting vibrations of a belt conveyor supported by rotating rollers and detecting abnormalities in the rotating rollers from the vibration level, and a vibration sensor for detecting abnormalities in the rotating rollers.

[Conventional technology]

FIG. 3 is a configuration diagram of the belt conveyor. A belt conveyor used for conveying coal, iron ore, etc. carries a conveyed object 17 as shown in Fig. 3, and has a rubber belt 16 that moves at a constant speed and supports the weight of the belt 16 and the conveyed object 17. It consists of a rotating roller 14 that smoothly guides a bell 16, and the rotating roller 4 is fixed to a frame 15. The rotating rollers 16 are usually made up of three rollers as a belt 16.
are placed at regular intervals on the conveyor line. Therefore, the number of rotating rollers per line reaches several hundred. The rotating roller 14 generally has a simple structure in which an iron cylinder is supported by two rolling bearings, but when operated for many years, the following problems occur. ■Rotating rollers do not rotate smoothly due to damage to rolling bearings or poor lubrication. ■The cylindrical surface of the rotating roller wears unevenly, causing irregular rotation. If such a phenomenon occurs, ■The belt may meander and become detached from the rotating rollers, causing the load to collapse or the machine to be unable to operate. ■Belt wear progresses and shortens its life. For this reason, rotary rollers in which abnormalities occur are replaced one by one, but abnormalities are detected by regular patrol inspections by specialized workers, and the inspection method is as follows. ■Visually inspect the rotating roller for abnormal rotation (backlash, eccentric rotation, etc.). ■Check for odors caused by abnormal heating of grease, etc. ■Visually inspect the wear debris accumulated on the frame. ■Check for abnormal sounds.

[Problem to be solved by the invention]

Conventional patrol inspections by specialized workers involve visual, auditory, and olfactory senses, which has the following drawbacks. ■Unless the abnormality in the rotating roller progresses significantly, it is difficult to discover the abnormality. ■Since individual differences among patrol workers are added to abnormality determination, the accuracy of determination varies widely and accuracy is low. ■According to regular patrols, the large number of rotating rollers delays the discovery of abnormalities and makes it impossible to detect sudden accidents. The present invention solves the above-mentioned drawbacks and compares changes in the vibration level at a frequency equal to the resonant frequency of the frame supporting the bearings of the rotating rollers of a conveyor device that conveys goods by a belt supported by a plurality of rotating rollers. It is an object of the present invention to provide a method for detecting an abnormality in the rotating roller and a vibration sensor for detecting the abnormality.

[Means to solve the problem]

The method for detecting an abnormality in a rotating roller for the above purpose is to detect an abnormality by measuring in advance the resonance frequency of a frame that supports the bearings of the rotating roller in a belt conveyor device that conveys cargo using a belt supported by a plurality of rotating rollers. Continuously extract the vibration level at a frequency equal to the resonant frequency during operation of the frame, and compare this extracted value with the vibration level at a frequency equal to the resonant frequency during normal operation of the frame, This is achieved by a method for detecting an abnormality in a rotating roller for a belt conveyor, which detects an abnormality in the rotating roller from a change in the extracted value. Furthermore, the vibration sensor for the above purpose detects a vibration level of a frequency equal to the resonant frequency of a frame supporting the bearings of the rotating rollers in a belt conveyor device that conveys cargo with a belt supported by a plurality of rotating rollers. a piezoelectric vibration detector that is fixed to the frame and detects vibrations on the frame surface as a charge signal; a charge circuit that converts the charge signal of the piezoelectric vibration detector into a voltage signal; and a charge circuit that converts the charge signal of the piezoelectric vibration detector into a voltage signal. a bandpass filter circuit whose center frequency can be arbitrarily set so as to extract a signal having a frequency equal to the resonant frequency of the frame from among the output signals of the frame, and an amplifier circuit which amplifies the output signal of the bandpass filter circuit; It consists of a process signal circuit that converts the output signal of this amplifier circuit into a DC signal, and is achieved by an integrated vibration sensor.

[Function] As a result of experiments, it is known that the resonant frequency of the frame that supports the bearing of the rotating roller of the belt conveyor matches the frequency band of the dominant peak spectrum of the frame. By comparing the change in the vibration level of the frame with respect to the number of vibrations, it is possible to detect an abnormality in the belt conveyor rotating roller. According to the vibration sensor of the present invention, the vibration of the frame that supports the rotating roller of the belt conveyor is detected as vibration acceleration by a piezoelectric vibration detector that is highly sensitive in a high frequency band, and only the resonant frequency component of the frame is detected from the vibration acceleration. A band-pass filter circuit detects the output, amplifies this output, and a process signal circuit converts the signal into an easy-to-handle DC signal. By comparing the level, it is possible to detect an abnormality in the roller.

【Example】

The present invention will be described in detail below based on the drawings. FIG. 1 is a circuit diagram of a vibration sensor used in a belt conveyor rotating roller abnormality detection method according to an embodiment of the present invention, FIG. 2 is an external view of the vibration sensor of FIG. 1, and FIG. 3 is a configuration diagram of a belt conveyor. FIG. 4 is a system diagram for monitoring an abnormality in a rotating roller, which systematizes the method for detecting an abnormality in a rotating roller according to an embodiment of the present invention. In FIG. 3, the bearings of three rotating rollers 14 are each supported by a frame 15, a belt 16 is placed on the rotating roller 14, and a conveyed object 17 is placed on this belt for movement. A vibration sensor 13 is attached to the frame 15. This invention provides a vibration sensor attached to the frame 15 that measures in advance the resonance frequency of a frame 15 that supports the bearing of the rotating roller 14, and detects a vibration level of a frequency equal to the resonance frequency during operation of the frame 15 to detect an abnormality. 13, and compare this extracted value with the vibration level at a frequency equal to the resonant frequency during normal operation of the frame 15, and based on the change in the extracted value, the rotation roller 14
now detects abnormalities. 5 and 6 show the relationship between the frequency spectrum and amplitude (G value) of the vibration acceleration of the frame 15 detected by the vibration sensor 13, and the numerical values written above the waveform diagrams are as follows:
It shows the relationship between amplitude and frequency from the largest amplitude to the 10th largest amplitude. FIG. 5 shows the frequency spectrum of the normal vibration acceleration of the rotating roller, and FIG. 6 shows the frequency spectrum of the abnormal vibration acceleration of the rotating roller. The rotation speed of the rotating roller 14 is approximately 800 rpm. Comparing the two spectra, ■The frequencies of the dominant peak spectra of both are from 460k to 522.5H.
It is concentrated in the z band. ■The maximum peak level of the abnormal roller reaches three times the maximum peak level of the normal value. ■As a result of the experiment, it was found that the frequency component of 460 to 552.51 (z) coincides with the resonant frequency at which the vibration detector was attached. ■With an abnormal roller, the frequency component near the peak also increases, so It can be seen that the transmitted excitation force is impulsive and irregular.Generally, when a rotating object such as a roller becomes abnormal, the fundamental component has a frequency equal to the rotational speed of the roller, and its integral multiple components However, in the experimental results, these phenomena were not observed.The reason is that the rotating roller 14 of the heald conveyor
This is because the rotational speed is constantly changing and the vibrations accompanying the movement of the belt 16 are superimposed and transmitted as excitation force to the frame 15. The vibration sensor 13 according to the present invention will be explained below. In FIGS. 1 to 3, the vibration sensor 13 is fixed to the frame 15 so as to detect a vibration level having a frequency equal to the resonant frequency of the frame 15 supporting the bearing of the rotating roller 14. A piezoelectric vibration detector 1 detects the vibration of the piezoelectric vibration detector 1 as a charge signal, and a charge circuit 2 converts the charge signal of the piezoelectric vibration detector 1 into a voltage signal.
, a bandpass filter circuit (hereinafter referred to as a BPF circuit) 3 whose center frequency can be arbitrarily set so as to extract a signal having a frequency equal to the resonant frequency of the frame 15 from the output signal of the charge circuit 2; It consists of an amplifier circuit 4 that amplifies the output signal of the circuit 3, and a process signal circuit 5 that converts the output signal of the amplifier circuit 4 into a DC signal, and is integrally constructed. 6 is a DC 24V line, 7 is a signal output line, and 8 is a common line. The operation of this vibration sensor 13 will be explained below. The piezoelectric vibration detector 1 uses a compression type, one-curve distortion type, a shear type, or the like. The vibration detected by the piezoelectric vibration detector 1 is converted into a voltage signal by a charge circuit 2 since it is a charge signal proportional to the acceleration of the vibration. The voltage signal of the charge circuit 2 is transmitted to the BPF circuit 3.
Only vibration signals equal to the resonance frequency of the frame 15 are extracted. The bandpass filter of BPF circuit 3 is l/3
It has an octave frequency cut-off time, and its center frequency can be set according to the resonance frequency of the frame. Therefore, before using the vibration sensor 13, the resonance frequency of the frame is measured in advance using a vibration analyzer such as FFT, and the center frequency of the BPF circuit 3 is set. Since this BPF circuit 3 extracts the vibration level of all peak components of the passband width, it is possible to magnify the vibration level generated from the abnormal roller. For example, the peak component (485
7, 410Hz, 460) fz) and the 6 peak components in Figure 5 are measured in 1/3 octave, the respective overall values are 1.026 G when normal and 4 when abnormal.
．． At 94G, the magnification is 4.7 times, increasing the detection sensitivity. The voltage signal from the BPF circuit 3 is amplified by an amplifier circuit 4 and then converted into a DC voltage signal or current signal by a process signal circuit 5. For example, if you output a DC current of 4 to 20 mA for intensive monitoring at a distance, it can be transmitted over a distance of 300 to 500 m, and if you want to convert it to a voltage signal, insert a 250 Ω load resistor to obtain a DC voltage of 1 to 5 V. be able to. The output signal of the process signal circuit 5 is generated on a signal output line 7 and a common line 8, and by connecting a commercially available recorder to these, data proportional to vibration can be recorded or read as a vibration level. The operating voltage of the vibration sensor 13 is DC 24
V and is supplied between the DC24V line 6 and the common line 8. FIG. 2 is an outline diagram of the vibration sensor 13 incorporating the circuit shown in FIG. 1. The lower case 10 and the upper case 11 are integrated with fixing screws 12 and can be extended to any desired length. FIG. 3 is a configuration diagram of the belt conveyor device. A vibration sensor 13 according to the present invention is attached to a frame 15 of a rotating roller 14. The belt 16 carrying the conveyed object 17 is fixed by a rotating roller 14.
The frame 15 vibrates due to the excitation force generated. In this example, since three rotating rollers 14 are fixed to the frame 15, the vibration sensor 13 is connected to the three rotating rollers 14.
Even if any of the rotating rollers 14 becomes abnormal due to the vibration generated by the excitation force, the abnormality can be detected. FIG. 4 shows an example in which abnormality monitoring of a belt conveyor line is systemized. There are numerous frames 15 shown in FIG. 3, and a vibration sensor 13 is attached to each frame 15. The output signal of the vibration sensor 13 can be switched by the scanner (IH7) according to instructions from the central processing unit 20.Scanner (1) 17
The output signal of the vibration sensor 13 selected in is compared with the normal vibration value by the comparator 18, and the output signal is "good" or "warning". It is classified into three levels: ``Danger''. The determined data is
Together with the number of the vibration sensor 13, the information is inputted to the central processing unit 20 via the scanner (2) 19 which operates under the instructions of the central processing unit 20, and displayed on the display.

【Effect of the invention】

This invention measures the resonant frequency of a frame that supports the bearing of a rotating roller in advance, continuously extracts the vibration level at a frequency equal to the resonant frequency during the operation of the frame to be detected for an abnormality, and uses this extracted value and The vibration level at a frequency equal to the resonant frequency of the frame during normal operation is compared, and an abnormality in the rotating roller is detected from a change in the extracted value, so that the vibration of the frame can be continuously monitored. , has the following effects. ■Since abnormalities in rotating rollers can be detected before they are minor, the life of the conveyor belt can be extended without damaging it. In addition, sudden accidents can be avoided and the operating rate of the conveyor line can be improved. ■Compared to conventional visual, auditory, olfactory, etc. methods, there are no individual differences in abnormality detection and the accuracy is high, so abnormal rollers can be detected without experience or skill. ■Repair costs can be reduced because the rotating rollers are repaired in a planned manner. ■Since patrol inspection work is no longer required, labor and personnel can be reduced, and the danger of work is also eliminated. Furthermore, the vibration sensor according to the present invention includes a piezoelectric vibration detector that detects vibrations on the frame surface as a charge signal, a charge circuit that converts the charge signal of the piezoelectric vibration detector into a voltage signal, and an output of the charge circuit. A PF circuit whose center frequency can be arbitrarily set so as to extract a signal having a frequency equal to the resonant frequency of the frame from among the signals, and this BPF.
It consists of an amplifier circuit that amplifies the output signal of the circuit, and a process signal circuit that converts the output signal of the amplifier circuit into a DC signal, and because it is integrated, it has the following effects. ■The filter of the BPF circuit can be set arbitrarily according to its center frequency and the resonance frequency of the frame, so it can be used even if the type and size of the conveyor changes. ■Since the detected frame vibration is converted into a DC signal, the signal can be easily handled and processed. ■Also, since the vibration sensor is integrated, on-site wiring, repair, and handling become easier.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a vibration sensor used in a belt conveyor rotating roller abnormality detection method according to an embodiment of the present invention, and FIG.
3 is a configuration diagram of a belt conveyor, FIG. 4 is a system diagram for monitoring abnormalities in rollers systematizing a method for detecting abnormalities in rotating rollers according to an embodiment of the present invention, and FIG. The figure shows the frequency spectrum of the normal vibration acceleration of the rotating roller, and FIG. 6 shows the frequency spectrum of the abnormal vibration acceleration of the rotating roller. l: Piezoelectric vibration detector, 2: Charge circuit, 3: BPF circuit, 4: Amplification circuit, 5: Process signal circuit, 7: Signal output line, 13: Vibration sensor, 14: Rotating roller, 15: Frame, 16 : Belt, 17: Conveyed object.

Claims (1)

[Claims] 1) In a belt conveyor device that conveys cargo using a belt supported by a plurality of rotating rollers, the resonant frequency of the frame that supports the bearings of the rotating rollers is measured in advance, and the resonance frequency of the frame to be detected for abnormality is determined. Continuously extract the vibration level at a frequency equal to the resonant frequency during operation, compare this extracted value with the vibration level at a frequency equal to the resonant frequency during normal operation of the frame, and determine the extracted value. A method for detecting an abnormality in a rotating roller for a belt conveyor, characterized in that an abnormality in the rotating roller is detected from a change in the rotation roller. 2) In a belt conveyor device that conveys cargo with a belt supported by a plurality of rotating rollers, the vibration sensor detects a vibration level with a frequency equal to the resonance frequency of a frame supporting the bearings of the rotating rollers. a piezoelectric vibration detector that detects vibrations on the frame surface as a charge signal; a charge circuit that converts the charge signal of the piezoelectric vibration detector into a voltage signal; A bandpass filter circuit whose center frequency can be arbitrarily set to extract signals of equal frequency, an amplifier circuit that amplifies the output signal of this bandpass filter circuit, and converts the output signal of this amplifier circuit into a DC signal. A vibration sensor characterized in that it is composed of a process signal circuit and is integrally configured.