JPS6237512A - Metallic contact detector at slide bearing section - Google Patents

Abstract

PURPOSE:To comprehend occurrence of bearing metal contacting phenomenon in early stage by taking out only low frequency ultrasonic signal to be produced through bearing metal contact thus detecting metallic contact. CONSTITUTION:Signals are envelope detected through detecting circuit 8a then passed to low frequency BPF8b thus to eliminate D.C. component and to take out only low frequency signal characteristic of bearing metal contact. Consequently, slight variation of signal caused through bearing metal contact which is not clear in the output waveform from the detecting circuit 8a can be comprehended clearly. As a result, occurrence of bearing metal contact can be displayed in early stage on a display unit 11.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metal contact detection device for a bearing portion of a rotating machine.

Conventionally, sliding bearings and the like used in rotating machinery have a phenomenon in which metal-to-metal contact occurs between the journal and the bearing Babbitt metal (hereinafter referred to as bearing-metal contact) due to breakage of the lubricating oil film due to excessive bearing load or poor alignment between the bearing and journal. ), which is known to cause bearing burnout accidents.

Conventionally, metal temperature measurement methods, bearing waste oil temperature measurement methods, and the like have been used as means for monitoring bearing burnout, and these methods will be described below. Friend number one
As shown in the figure, what happens when bearing metal contact occurs due to poor alignment between journal 1 and Babbitt metal 2, so-called bearing uneven contact? Assume. The above-mentioned nine metal temperature measurement method involves installing a thermocouple 4a4 in the bearing back plate 3, and measuring all the thermal changes that occur when the pavit metal burns out due to contact with one part of the bearing, as shown in part (■) in Figure 1. It is a means to monitor everything. On the other hand, the bearing drain oil temperature measurement method involves installing a thermocouple 41) f in the cover member 5 and measuring the thermal change that occurs when the pavit metal burns out due to the contact with the bearing piece shown in section ``■'' in Figure 1 through the drain oil. This is a means of monitoring burnout of Babbitt metal, etc.

However, in the metal temperature measurement method described above, the thermocouple 4a is installed inside the bearing back metal 3 and is further away from the bearing sliding surface at a position t. There are cases where it is not possible to detect the abnormality, and the abnormality can only be detected after the Babbitt metal has burned out to some extent. The same applies to the bearing oil temperature measuring method described above.

In addition to the measurement methods described above, there is a method of measuring changes in aluminium using a gap sensor, which is a method of attaching a strain gauge to the bearing body and detecting abnormalities from changes in the strain value, but these methods only work after the Pavisotometal burnout has progressed to a certain extent. Therefore, it was difficult to initially detect bearing metal contact that could lead to bearing burnout.

SUMMARY OF THE INVENTION An object of the present invention is to provide a metal contact detection device for a bearing portion that can detect a bearing metal contact phenomenon as soon as it occurs.

The feature of the present invention is that an acoustic detection element is attached to the shaft and the bearing, and this acoustic detection element receives acoustic signals such as ultrasonic waves generated due to bearing metal contact, and processes this signal to prevent bearing burnout. The key point is that the bearing metal contact phenomenon that is the cause is detected at an early stage.

The present invention will be explained in detail below using the drawings. FIG. 2 shows a block diagram of a metal contact detection device for a bearing portion, which is a specific embodiment of the present invention. An acoustic detection element 3 (FC, for example, using a piezoelectric ceramic element) is installed by full pressure bonding or adhesive at a location where it can detect the ultrasonic signal generated due to the bearing metal contact phenomenon of the bearing 2 that supports the journal 1,
The signal obtained by the acoustic detection element 3 is input to a total preamplifier 4.

Next, the signal amplified by a preamplifier 4 is passed through a filter 5 to remove noise. Further, all noise is removed, the 'c signal is further amplified by the twin main amplifier 6, and the signal is input to the total rotation speed determination circuit 4. The rotation speed determination circuit 7 takes in the rotation speed of the journal and determines whether it is turning (approximately 2r[)m) or the operating state, and only when the operating state is in progress, the output signal from the main amplifier 6 is used to discriminate bearing metal contact. Input to circuit 8. The bearing metal contact discrimination circuit 8 includes a detection circuit 3a and a band pass filter (hereinafter abbreviated as BPF) Bb.
, an amplifier 8c, and a detector 8d. Reference numeral 9 denotes a comparator circuit which compares the signal output from the detection gtscl with the comparison voltage of the comparator circuit 9, and converts the t signal exceeding the comparison voltage into a square wave.

A bearing metal contact determination circuit 10 is a circuit that outputs a signal when the number of signals output from the comparison circuit 9 per unit time exceeds a predetermined t value, and 11 is a display device; This device displays whether or not a bearing metal contact phenomenon has occurred based on a signal output from the bearing 10.

Here, the operating principle of the above-mentioned metal contact detection device for a bearing portion will be explained in detail. FIG. 3 shows the operation of each circuit and its output waveform separately for cases in which bearing metal contact occurs and cases in which there is no bearing metal contact for ease of understanding when explaining the operating principle of the bearing metal contact detection device. As shown in the figure, the ultrasonic signal output waveform (output waveform of the main amplifier 6) when there is no bearing metal contact is mainly a waveform due to noise generated by rotation of the journal, circulation of lubricating oil, etc. On the other hand, the ultrasonic signal output waveform when there is bearing metal contact is characterized in that the signal due to bearing metal contact is slightly superimposed on the waveform due to the above-mentioned noise, resulting in a so-called modulated wave. The cause of this signal is that the low frequency signal generated when the bearing metal contacts is superimposed on the waveform caused by the noise mentioned above.

First, the operation of each circuit when bearing metal contact occurs will be explained. The above-mentioned ultrasonic signal is passed through a rotation speed determination circuit 7 and then inputted into a bearing metal contact discrimination circuit 8. 8, first, the signal is envelope-detected by the detection circuit 8a as shown in the figure, and then a low frequency (less than 200Hz) BPF is detected.
8b, the direct current component is removed and only the low frequency signal, which is characteristic when the bearing is in contact with metal, is extracted, as shown in the figure. By performing all of these operations, there was a slight signal change due to the bearing metal contact, which was unclear in the output waveform of the detection circuit 8a. It can be clearly understood. Next, the signal is amplified by an amplifier 8C, and then passed through a detector 8d to obtain the waveform shown in the figure. Next, the comparison circuit 9
By comparing with the comparison voltage Ev, the square wave signal shown in the figure is obtained as the output of the comparison circuit 9. Next, the number of occurrences per unit time of this square wave is set to a nine-threshold? In this case, as shown in the figure, a signal is output from the bearing metal contact determination circuit 1o, and the occurrence of bearing metal contact is displayed on the display device @11.

In addition, in the bearing metal contact determination circuit described above, the output waveform of the comparison circuit 9 shown in FIG. The determination may be made when 100 pulses are output.

Next, the operation when there is no bearing metal contact will be explained.

The ultrasonic signal shown in FIG. 3 is passed through the rotation speed determination circuit 7,
Next, it is input to the bearing metal contact discrimination circuit 8. 8, the signal is first detected by the detection circuit 8a as shown in the figure, and then passed through a low frequency BPF to obtain the waveform shown in the figure. As can be seen from the figure, when there is no bearing metal contact, unlike the case where bearing metal contact occurs, the signal is mainly due to noise, so only the DC component is removed. Next, the signal amplifier 8C
The waveform shown in the figure is obtained by amplifying the signal and passing it through a detector 8d. Next, a comparison is made using the comparison voltage E7 of the waveform total comparison circuit 9. If there is no bearing metal contact, as shown in the figure, the waveform detector 8d
Since the amplitude of the signal output from Ev is much smaller than Ev, the comparison circuit 9 will not generate a square wave. As a result, the bearing metal contact determination circuit 10 does not generate an output signal as shown in the figure, so the display device 11 completely displays that no μ bearing metal contact has occurred.

As explained above, by performing signal processing that extracts only the low-frequency ultrasonic signals generated by bearing-to-metal contact, it is possible to detect the occurrence of bearing-to-metal contact at an early stage and clearly, which can lead to bearing burnout. It can be used as an online monitor for detecting bearing metal contact phenomena, and has an extremely effective and remarkable effect industrially.

[Brief explanation of the drawing]

FIG. 1 is a model diagram for explaining the entire bearing metal temperature and bearing exhaust oil temperature measuring method. FIG. 2 is a block diagram of a metal contact detection device for a bearing portion according to the present invention. FIG. 3 is a waveform chart for explaining the operation of the metal contact detection device for a bearing portion according to the present invention. 3...Acoustic detection element, 8...Bearing metal contact discrimination circuit.

Claims (1)

[Claims] 1. An acoustic detection element that detects ultrasonic waves generated by metal contact between a journal of a rotating machine and a bearing metal of a sliding bearing used in the rotating machine; An amplifying section that amplifies the signal, a discriminating section that takes in the output from the amplifying section and extracts only the low frequency component, and compares the signal output from the discriminating section with a predetermined reference value to determine the above-mentioned output. a comparison circuit that generates a square wave when the signal is greater than the reference value;
A metal contact detection device for a sliding bearing, comprising a determination circuit that receives a square wave output from the comparison circuit and determines whether there is a metal contact with the bearing, and a display section that displays the output of the determination circuit. 2. A rotation speed determining circuit is provided between the widening section and the discriminating section, and the rotation speed determining circuit applies the output of the widening section as an input to the discriminating section only when the rotating machine is operating other than during turning operation. A metal contact detection device for a sliding bearing portion according to claim 1.