JPS5940267B2 - Damage detection device for rotating bodies - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a damage detection device for a rotating body, and in particular detects damage to a bearing by evaluating the average peak value of intermittent shock vibrations that occur when a damaged bearing rotates. Concerning improvements to equipment.

Mechanical vibrations that occur when rotating a rotating body, such as a bearing, are detected by a pickup and converted into an electrical signal. Frequency components unnecessary for signal processing are removed by a filter, and the peak value of the output signal from the filter is A damage detection device for a rotating body of the type that detects damage to a rotating body by detecting the damage and evaluating the average of the damage is disclosed in Japanese Patent Application No. 79111/1987 (1983) filed by the applicant.
It is disclosed in Japanese Patent Application Laid-Open No. 51-8990).

According to the above-mentioned device, the peak value of vibration is detected by a peak value detector with reset.

The detector is reset at predetermined intervals by pulses from a pulse generator that are generated with an adjusted period, detects peak values one after another during the period, and maintains the level. be. The output of the detector is then integrated by a normal integrating circuit, and if the integrated value, that is, the average of the peak values, is above a predetermined level, it is determined that the rotating body is damaged. In such a damage detection device for a rotating body, peak value detectors are set at predetermined intervals in order to eliminate the influence of accidental noises etc. that are not caused by damage to the rotating body when detecting damage to the rotating body. ing.

It is therefore clear that a pulse generator is needed to generate the reset pulses. Such damage detection devices for rotating bodies are valuable enough to be used for high-precision damage detection, but in facilities where a large number of bearings are used in power plants, steel plants, etc., damage to individual bearings may occur. When attempting to centrally monitor by installing detection devices for each, we have to consider the problem of cost.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to simplify and downsize the structure of a damage detection device, thereby reducing costs.

Another object of the present invention is to provide an improved damage detector for a rotating body that does not require time and effort to adjust the period of the reset pulse when installing the damage detector.
According to a feature of the invention, no reset pulses are applied to the peak detection circuit in order to eliminate the effects of random disturbances such as noise.

That is, no pulse generator is used. In order to compensate the device for the effects of external disturbances, improvements have been made to the peak value detection circuit and the integration circuit. Details of these circuits will be given later, but the present invention will become clearer by describing the embodiments together with the drawings. In FIG. 1, a vibration pickup 1 converts mechanical vibrations of a rotating body, such as a bearing, into an electrical signal, and an amplifier 2 amplifies the output signal to an appropriate level.

The amplifier output waveform in this case is shown in FIG.
FIG. 2 shows the output waveforms of the individual circuit elements in the case of damage, assuming an ideal state with no accidental disturbances. The output of the amplifier 2 is applied to a band p-wave generator 3 to remove frequency components unnecessary for signal processing, and then applied to a peak value detection circuit. The output waveform of the band P wave generator 3 is shown in FIG. Peak value detection circuit 4}j detects the peak value of the input signal and generates an output waveform that discharges and attenuates according to a selected time constant.

The output waveform in this case is shown in FIG. 2. The condition here is that the discharge time constant is selected to be the minimum within a range that can substantially maintain the peak value of periodic shock vibrations that occur when the rotating body is damaged. That is, in FIG. 2 3, V
It is to satisfy le<<l. As described above, the reason why the detected peak value is attenuated by discharge is to remove the influence of disturbance. Each occurrence of noise due to external disturbances is sudden, and there are few cases that occur at quick periodic intervals, such as vibration shock waves caused by scratches on a rotating body. However, if the discharge decays according to an appropriate time constant without being held, then it can be averaged (i.e., integrated) over a long period of time.
If so, the value becomes negligible. Therefore, damage detection of the rotating body is not affected. The specific circuit configuration of the peak value detection circuit 4 described above (will be explained later using FIG. 4).The output of the peak value detection circuit 4 is applied to the pseudo-integrator circuit 5 and integrated (see 4).

In the pseudo-integrator circuit 5, the time constant for determining its discharging time is selected to be sufficiently smaller than the time constant for determining its charging time. As mentioned above, when we assume an ideal case where there is no disturbance, or when we assume that even if there is a disturbance, it will occur sporadically with a sufficiently long interval (or not necessarily). Although this is not necessarily necessary, if we assume that noise due to disturbance occurs continuously at non-negligible intervals as a real problem (
In addition, countermeasures are needed. Therefore, for this purpose, the discharging time constant (or charging time constant) of the pseudo-integrator circuit is selected to be a sufficiently small value compared to the charging time constant.This point will be discussed in detail later. The output of the pseudo-integrator circuit when there are

If the bearing is not damaged, the output voltage of the pseudo-integrator circuit 5 will be at a DC level proportional to the steady vibration amplitude of the bearing.

On the other hand, as shown in FIG. 2 and 3, when damage occurs to the bearing, the output voltage of the pseudo-integrator circuit 5 becomes a DC level proportional to the peak value of the shock vibration caused by this damage.
The voltage value is much larger than that in the case where there is no damage.
The output voltage obtained in this way (well, it is generally proportional to the degree of bearing damage, so by displaying this output voltage on a meter or activating an alarm or relay when it exceeds a set value, it is possible to It is possible to detect damage at an early stage. FIG. 4 shows a specific example of the circuit of the peak value detector 3.

In FIG. 4, the output from the band P-wave device 3 is applied as an input to the input terminal. Input terminal 1 is connected to the non-inverting input terminal + of operational amplifier A, and its output side is connected to output terminal 0 via diode D1. Output terminal 0 is connected to the inverting input terminal - of operational amplifier A via feedback resistor R1, and furthermore, output terminal 0 is grounded by capacitor C1 and resistor R2 which are parallel to each other. Now, when the input terminal 1 receives the output from the waveform generator 3, the operational amplifier A operates to detect the peak value.

Since the diode D1 is connected in the forward direction to the output side of the operational amplifier A, the output terminal 0 is connected in accordance with the time constant determined by the product of the forward resistance of the diode and the capacitance of the capacitor C1. The peak value voltage detected by the operational amplifier A is instantaneously generated. Thereafter, at output terminal 0, said peak value voltage decays according to a discharge time constant determined by the product of capacitor C1 and resistor R2. Time constant Cl, R2
The value of is selected based on the above-mentioned conditions l-e, taking into consideration the periodic interval of shock vibration waves generated due to expected damage to the rotating body.
《It can be determined to be the minimum within the range that satisfies i.

FIG. 5 shows a specific circuit example of the pseudo-integrator circuit 5.

Here, in addition to the usual integration circuit configuration consisting of a resistor R3 and a capacitor C2, a diode D2 is connected in parallel to the resistor R3.
is connected. As is clear from the figure, the charging time of the pseudo-integrator circuit is determined by the product of the time constant C2R3. On the other hand, regarding the discharge time, considering that the input of the pseudo-integrator circuit 5 is connected to the output 0 of the peak value detection circuit shown in FIG. It is determined by the discharge resistance R2 in the head value detection circuit 4. That is, time constant C2 (R2+Rd)
determined by. If we remember that the discharge time of the pseudo-integrator circuit 5 is sufficiently fast, it is clear that the relationship between the resistors R2 and R3 (R2<R3 must be satisfied) is as described above. Next, the operation of the rotating body damage detection apparatus of the present invention having the above-mentioned structure when an accidental disturbance is received will be described.

It is assumed that the output of the band P-wave device 3 has an output waveform as shown in FIG. 3 due to the current incidental disturbance.

Figure 3 (For convenience of drawing, the time scale of the horizontal axis is reduced from the time scale of Figure 2. In other words, the generation of noise depends on the generation period of vibration waves caused by scratches on the rotating body. The time axis scale in Fig. 3 is considerably reduced compared to the time axis scale in Fig. 2, since it is assumed that the output waveforms appear at sufficiently long intervals.Also, the amplitude value of the output waveform 2 and 3 are also shown on a reduced scale for convenience of drawing.Thus, although FIGS. 2 and 3 cannot be viewed in correspondence, the output of the peak value detector 3 is shown as shown in FIG. 32.

Further, the output of the pseudo-integrator circuit 5 is shown as a solid line in FIG. As mentioned above, the charging time of the pseudo-integrator circuit 5 is substantially determined by the time constant C2R3, and the discharging time is determined by the time constant C2R2.
Since R2<<R3, and the time constant C2R3 that determines the charging time is given as a large value, the rise of the output of the pseudo-integrator circuit 5 has a shadow, and its fall is detected by peak value detection. The falling speed of the output of the device 4 can be approximated to almost the same speed. Therefore, the output waveform of the pseudo-integrator circuit 5 becomes as shown by the solid line in Figure 3, and even in the worst case where noise is continuously applied as in the example, the final output amplitude is the same as that caused by one flaw. It is sufficiently small compared to the width, making it possible to distinguish between scratches on the rotating body and noise.

On the other hand, if a normal integrating circuit, that is, an integrating circuit with the same charging and discharging time constant is used instead of the pseudo-integrating circuit 5, the output of the integrating circuit will be as shown by the broken line in Fig. 3, and the peak value detector due to noise will be Since the outputs of 3 are accumulated in the integrating circuit, it may become impossible to distinguish between the output due to scratches on the rotating body and the output due to noise. As is clear from the above description, by using the pseudo-integrator circuit, the influence of disturbances can be minimized and damage to the rotating body can be evaluated with higher accuracy.

Regarding this point, it is clear that the same effect can be obtained even if the noise occurs sporadically rather than continuously in a fast cycle as in the previous example.Therefore, the present invention (: simple A damage detection device for a rotating body having a circuit structure is obtained, and such a detection device is particularly effective when used in large quantities.

[Brief explanation of the drawing]

FIG. 1 is a block diagram schematically showing a circuit configuration of a damage detection device for a rotating body according to the present invention.

Claims (1)

[Claims] 1. Converting mechanical vibration or sound generated when a rotating body is rotated into an electrical signal, and detecting damage to the rotating body from the amplitude of the electrical signal caused by scratches on the rotating body. The device includes: a peak value detection circuit having a characteristic of detecting the peak value of the electrical signal and discharging it according to a specific time constant; and a peak value detection circuit having a characteristic that the discharge time constant is sufficiently smaller than the charging time constant. A damage detection circuit for a rotating body, comprising a circuit that integrates the output of the selected peak value detection circuit. 2. The damage detection device for a rotating body according to claim 1, wherein the peak value detection circuit includes an operational amplifier; and a discharge circuit including a resistor R_2 and a capacitor. damage detection device. 3. In the damage detection device for a rotating body according to claim 1 or 2, the discharge time constant of the peak value detection circuit is an electrical signal caused by periodically occurring scratches on the rotating body. A damage detection device for a rotating body, characterized in that an amount of amplitude attenuation that is attenuated during one cycle of the electric signal is selected to be sufficiently smaller than the amplitude of the electric signal. 4. The damage detection device for a rotating body according to claim 1, wherein the pseudo-integrator circuit includes a capacitor, a resistor, and a diode connected in parallel to the resistor. Detection device. 5. In the damage detection device for a rotating body according to claim 2, the device further includes: a pseudo-integrator circuit including a capacitor, a resistor, and a diode connected in parallel to the resistor R_3; A damage detection device for a rotating body, characterized in that a relationship between a resistance R_2 of a discharge circuit of the value detection circuit and a resistance R_3 of the pseudo-integrator circuit is selected so as to satisfy R_2<<3.