JPH05231992A - Abnormality detection method of low speed rotation bearing - Google Patents

Abstract

PURPOSE:To early and surely detect the abnormality of bearings by measuring a vibration speed in a stationary state of no-load and a cetain rotating speed of a rotary machine and judging the presence of damage with the vibration speed compared with an initial value thereof. CONSTITUTION:Within a vibration speed detector 1 the mechanical vibration of bearings 3 for supporting an extension roll 2 is converted into an electric signal and input to a data taking-in judgement device 5. In addition, rolling load is input from a load cell 6 and the rotating speed of a drive electric motor 7 is input from a rotating speed detector 8 to the judgement device 5. The no-load of the extension roll 2 measured just after the change of the bearings 3 and the initial value of a vibration speed in a stationary state of a certain speed are store within the judgement device 5. And the rolling load input from the load cell 6 is zero, the vibration speed input from the detector 1 in the stationary state of a certain rotating speed input from another detector 8 is compared with the stored initial value and the bearings 3 is judged to be abnormal at the time point where the input vibration speed is specified times as large as the initial value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing abnormality detecting method for detecting abnormality of a rolling bearing which is rotating at a low speed under conditions susceptible to vibrations of peripheral machines.

[0002]

2. Description of the Related Art When a rolling bearing incorporated in a rotary machine is damaged, shocking vibration having a period proportional to the number of revolutions is generated. Conventionally, the abnormality of the bearing is detected by an operator directly by the five senses, or by detecting the vibration generated from the bearing or the temperature thereof by using an appropriate detector. Generally, the abnormality determination of the rolling bearing is performed by using the acceleration of the vibration of the bearing casing or the shock vibration due to the collision between the rotating machine and the flaw of the bearing.

For example, the vibrations of the bearings at both ends of the rotating body are individually detected, and the deviation of the peak values of both detection signals is calculated after removing the external vibration by a bandpass filter, and based on the calculation result. A method for detecting an abnormality of a bearing (Japanese Patent Laid-Open No. 56-26226), in which mechanical vibration generated by the rotation of a rotating machine is converted into an electric signal, and the electric signal is different from the vibration peculiar to the rotation of the bearing. A bandpass filter that removes extraneous vibration, an envelope circuit that extracts the envelope waveform from the output electric signal waveform of the bandpass filter, and a first to obtain the effective value or average value of the envelope waveform from the output of the envelope circuit. 1 arithmetic unit, a second arithmetic unit for obtaining an effective value or an average value of an electric signal waveform from the output of the band pass filter, an output of the first arithmetic unit and a second arithmetic unit And a third arithmetic unit that calculates the ratio of the force giving the envelope index apparatus for identifying the presence or absence of flaws of the bearing by evaluating the envelope index (JP 5
No. 8-127142), or an AE conversion element for converting crack sound generated from a rolling bearing into an electric signal, a discriminator for discriminating a predetermined level or more in the output of the AE conversion element, and an output of the discriminator. However, a device provided with an abnormality notifying means for notifying an abnormality of the rolling bearing when this is a predetermined value or more (Japanese Patent Laid-Open No. 61-294215), and further, an electric signal indicating mechanical vibration and sound generated by the rotation of the rotating machine. Detector, a peak value detector with reset that repeats detection-holding-reset operation of the peak value of the output signal of the detector, and a reset pulse for resetting the peak value detector with reset at a predetermined time interval It includes a generator and an integrator circuit for smoothing the output signal of the peak value detector with reset, and whether or not there is damage depending on the magnitude of the DC output voltage of the integrator circuit. Beauty device for detecting the magnitude of a number (JP-B 59-9842 Patent Publication), etc. proposals have been made.

[0004]

Among the above, when the determination is made by the average value of the output voltage, especially in a rotating machine of low speed rotation, the collision energy between the rotating machine and the flaw of the bearing is proportional to the square of the rotation speed. Since the number of impacts generated per unit time is small, the signal level of the average value after the envelope processing is very low, and it is difficult to distinguish it from noise. Further, when the determination is made by the peak value of the output voltage, although the signal level is higher than the average value, the peak value originally has a large variation in the value, which is not suitable for the determination.
Further, it may be easily affected by the vibration of the rotating machine body in which the bearing is installed or the peripheral machine, and it may be difficult to determine whether the signal is due to the damage of the bearing.

It is an object of the present invention to propose a damage detecting method for a low-speed rotary bearing which eliminates vibrations of the main body of a rotary machine or peripheral machines and which can obtain a parameter having a large signal level and a small variation.

[0006]

As a result of various studies to achieve the above object, the inventor of the present invention has found that the natural vibration of a flaw caused by the collision of the flaw between the rolling element and the bearing caused by the rotation of the rotating machine. It was clarified that the parameter was obtained as a parameter having a large signal level and a small variation, and the present invention was reached.

That is, the present invention provides a method for detecting an abnormality of a low-speed rotating bearing, which measures mechanical vibration of a bearing caused by rotation of a rotating machine and evaluates the mechanical vibration to detect the presence or absence of abnormality of the bearing. The vibration speed in a steady state with no load and a constant rotation speed is measured, and the presence or absence of damage is determined by comparing it with the initial value of the vibration speed in a steady state with no load and a constant rotation speed. ..

[0008]

According to the present invention, in order to eliminate the influence of the vibration of the peripheral machine, the vibration speed of the bearing is measured in a steady state of a rotating machine in which the bearing is installed under no load and at a constant number of revolutions. Since the presence or absence of damage is determined by comparing with the initial value of the vibration velocity of the bearing in a steady state where the rotating machine has no load and the rotation speed is constant, it is possible to eliminate the influence of the vibration of the peripheral machinery. The change in the signal level of the vibration velocity of the bearing caused by the damage of the bearing of the rotating machine is significantly larger than the initial value, and the change is abnormally large compared to the change of the vibration acceleration, and the abnormality of the bearing can be easily detected. Can be determined.

[0009]

【Example】

Embodiment 1 The details of the bearing damage determination method of the present invention will be described with reference to FIG. FIG. 1 is a control system diagram of an apparatus for carrying out the method of the present invention. In FIG. 1, reference numeral 1 denotes a vibration velocity detector, which is installed on a bearing 3 supporting a rolling roll 2 and converts mechanical vibration of the bearing 3 into an electric signal. The electric signal from the vibration velocity detector 1 is amplified by the amplifier 4 and then input to the data acquisition determination device 5. On the other hand, the data acquisition determination device 5 includes a load cell 6 for detecting the load of the rolling roll 2 and a rotation speed detector 8 installed in the driving motor 7 of the rolling roll 2 to detect the rolling load and the driving motor 7.
The rotation speed of is input. In addition, the data acquisition determination device 5
In the column, the initial value of the vibration velocity measured immediately after the replacement of the bearing 3 in the steady state in which the rolling roll 2 has no load and the rotation speed is constant is stored. Then, in the case of determining whether or not there is an abnormality in the bearing 3 by the data capture determination device 5, the data capture determination device 5 determines that the rolling load input from the load cell 6 is zero and the rotation input from the rotation speed detector 8 is the same. In a steady state where the number is constant, the vibration velocity input from the vibration velocity detector 1 via the amplifier 4 is compared with the initial value of the vibration velocity in the steady state measured immediately after the replacement of the bearing 3, and the vibration velocity is input. The bearing 3 is determined to be abnormal when the vibration speed reaches a predetermined value, for example, 20 times the initial value of the vibration speed of the bearing 3.

Because of the above-described configuration, in the determination of the presence or absence of abnormality of the bearing 3, the rolling load input from the load cell 6 is zero, and the rotation speed input from the rotation speed detector 8 is constant. Since the vibration speed input from the vibration speed detector 1 through the amplifier 4 is used, the influence of the vibration of the rolling roll main body and the vibration of the peripheral equipment is eliminated. Moreover, the vibration speed input from the vibration speed detector 1 to the data acquisition determination device 5 via the amplifier 4 is
Since the fluctuation due to damage is extremely large compared with the vibration acceleration, it is possible to easily detect the abnormality of the bearing.

Example 2 When a double row lead spindle roller bearing with a rotation speed of 117 rpm used in a rolling roll drive speed reducer of a rolling mill is replaced, a vibration detector is installed on the bearing to prevent the influence of vibration of peripheral machines. In order to remove it, the initial value of the vibration speed in a steady state in which the rolling roll was unloaded and the rotation speed was 117 rpm was measured. At the same time, the initial value of vibration acceleration was measured. as a result,
Vibration speed is 0.03 cm / sec, vibration acceleration is 0.5
It was G. After that, the secular change of the vibration velocity and the vibration acceleration in a steady state where the rolling roll of the bearing was unloaded and the rotation speed was constant at 117 rpm was measured. The result is shown in FIG.
As shown in Fig. 2, after two years have passed since the bearing was replaced, the vibration speed a became 20 times the initial value or more, so it was judged that the bearing was abnormal and disassembled, and the rolling surface of the bearing was observed. , There was a flaking flaw on the inner ring. On the other hand, FIG.
As shown in, the vibration acceleration b increased only about three times the initial value, and both the absolute value and the change were small, and it was difficult to determine the bearing.

[0012]

As described above, the method of determining abnormality of a bearing according to the present invention eliminates impacts and vibrations of peripheral machines other than a rotary machine in which a rolling bearing is installed, and a vibration velocity signal due to damage of the bearing. Since the abnormality due to the damage of the bearing is determined based on the vibration velocity whose level fluctuation is extremely large compared to the conventional vibration acceleration, the abnormality of the bearing can be detected early and reliably.

[Brief description of drawings]

FIG. 1 is a control system diagram of an apparatus for carrying out the method of the present invention.

FIG. 2 is a graph showing changes over time in measured values of vibration acceleration and vibration velocity in Example 2.

[Explanation of symbols]

 1 Vibration Speed Detector 2 Rolling Roll 3 Bearing 4 Amplifier 5 Data Acquisition Judgment Device 6 Load Cell 7 Drive Motor 8 Rotation Speed Detector

Claims (1)

[Claims] 1. An abnormality detection method for a low-speed rotating bearing, which comprises measuring mechanical vibration of a bearing caused by rotation of a rotating machine and evaluating the mechanical vibration to detect the presence or absence of abnormality in the bearing. It is characterized by measuring the vibration speed in a steady state with a constant rotation speed and comparing it with the initial value of the vibration speed in a steady state with no load on the rotating machine and a constant rotation speed to determine the presence or absence of damage. Bearing abnormality detection method.