JPS6226690B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vibration detection method for detecting shaft vibration of a rotating body such as a turbine or a motor.

A conventional device of this type is shown in FIG. In the figure, 1 is a cross-sectional view of the axis of the rotating body (the arrow indicates the direction of rotation), 2 is the case of the rotating body, 3 is a vibration detector that houses 4 and 5 pick-ups inside, 5a, 5b are components of the pick-up 5, 6a, 6b are high frequency oscillators, 7 is an adder, 8a, 8b, 8c are comparators, Pa,
Pb and Pc indicate the determination outputs of the comparators 8a, 8b, and 8c, respectively.

Next, the operation will be explained. The high frequency emitted by the oscillator 6b is supplied to the pick-up 4,
A voltage proportional to the gap between the rotary body 1 and the rotating body 1 is obtained and inputted to the comparator 8c and the adder 7. Vibration occurs in the rotating body 1, and the gap between the rotating body 1 and the pick-up 4 becomes small (large).
If the temperature increases, the eddy current in the pick-up 4 increases (decreases), and the eddy current from the oscillator 6b to the comparator 8 increases (decreases).
c and the output to the adder 7 are designed to become larger (smaller). The comparator 8c detects the increment (decrease) from the predetermined starting value, and if this value is above a certain value, it is determined that there is vibration and the output Pc
give a signal to The judgment of this signal Pc is
Since pick-up 4 is attached to case 2 of the rotating body, it detects the relative vibration between case 2 and rotating body 1, and if there is no vibration in case 2, the signal Pc will be correctly detected. 4 and the rotating body 1, that is, the vibration of the rotating body 1 is detected.

If the vibration in case 2 cannot be ignored, the signal
It is necessary to remove the vibration of the case 2 from the PC, and the pickup 5 takes measures for this. The pick-up 5 has an inertial structure. That is, the component 5a has inertia and does not move even if the case 2 vibrates. On the other hand, since the element 5b is vibrating together with the case 2, the pick-up 5 is detecting the vibration between the elements 5a and 5b, which means that the vibration of the case 2 is being detected. Therefore, the output of comparator 8a
Pa operates to output an output when the vibration in case 2 exceeds a certain value. The values from oscillators 6a, 6b applied to adder 7 are now added in a subtractive manner, ie, the signal from 6a is removed from the signal from 6b, and the output of adder 7 is The vibration between the pick-up 4 and the rotating body 1 is detected regardless of the presence or absence of vibration of the case 2. Therefore, the output Pb of the comparator 8b is used to determine the magnitude of vibration between the pick-up 4 and the rotating body 1, and is used to determine the vibration of the rotating body. These output signals Pa,
Pb and Pc have vibrations above a certain level and are used as a signal to stop a rotating body or to generate an alarm due to large vibrations. That is, the conventional device determines whether the instantaneous value of vibration is greater than or equal to a certain value.

The conventional devices described above have already been widely put into practical use, and there are no problems under normal circumstances. However, it has the following drawbacks.

(1) When there is a scratch on the shaft of the rotating body, the distance (gap) between the rotating body 1 and the pick-up 4 appears to change, making it appear as if vibration has occurred. This becomes a problem as the accuracy of vibration detection increases, and there is a risk of false detection.

(2) Increasing the precision of machining the shaft of the rotating body 1 increases the machining cost, making the vibration detection system expensive.

(3) Since a defect is known only when the vibration value exceeds a certain value, it is not possible to know about aging, which is a requirement for maintenance.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and by computer processing the information obtained from the vibration pickup,
The purpose of the present invention is to provide a vibration detection device that is inexpensive, highly accurate, and satisfies maintenance requirements.

The vibration detection device according to the present invention has a pick-up that outputs an output in response to each vibration in the rotating body and the case of the vibrating body, and the output of each of the pick-ups is input, and a predetermined value is determined from each input value. a calculation device that calculates the average vibration value between each
A reference value setting device is provided for determining the magnitude of vibration values of the rotating body and the rotating body case, and the vibration status of the rotating body is determined based on whether the output of the calculation device is larger or smaller than the output of the reference value setting device. It is a judgment.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows an embodiment of this invention, in which 9
a, 9b, 9c are calculation devices for calculating the average vibration value; 10a, 10b, 10c are reference value setting devices for determining the magnitude of the vibration value; 11a, 11b,
11c is a comparison device that compares the outputs of the calculation devices 9a, 9b, 9c and the reference value setting devices 11a, 11b, 11c, respectively; 12 is the various devices 7, 9a, 9b, 9c, 10a, 10b,
Computers 10c, 11a, 11b, and 11c constitute computers, and 13 is a tachometer that detects the rotational speed of the rotating body. Note that the same reference numerals in FIG. 2 as in FIG. 1 indicate the same or corresponding parts.

Next, the operation shown in FIG. 2 will be explained. Pick
The magnitude of the vibration detected at ups 4 and 5 is
As in the figure, the outputs become the outputs of the oscillators 6a and 6b, and are applied to the adder 7 and the average value calculation devices 9a, 9b, and 9c (through 7 to 9b). Computing devices 9a, 9
A signal from a tachometer 13 that detects the rotation speed of the rotating body 1, which is provided separately, is given to b and 9c.
If the output of the tachometer 13 is n revolutions/second, the time required for one rotation is 1/n second, and the average value of the vibration values in this time span is calculated by the average value calculation devices 9a, 9b, 9.
Calculate with c and output. This calculation device 9a, 9
The outputs of b and 9c are output from the standard value setting devices 10a and 10.
b, 10c output and comparison device 11a, 11b, 1
1c, and if the vibration output is larger than the standard value, it is determined that the vibration is large and an alarm is issued or a signal to stop the rotating body is sent to the output terminals Pa,
Send to Pb and Pc.

Adder 7, calculation devices 9a, 9b, 9 described above
c, reference value setting devices 10a, 10b, 10c, comparison devices 11a, 11b, 11c, etc. can be easily realized by constructing them with the computer 12.

Since FIG. 2 operates as described above, it can be determined whether the average value of vibration is above a certain value. Therefore, even when there is a flaw on the shaft of a rotating body, if the flaw is sufficiently small relative to the circumference of the shaft, conventional devices would incorrectly detect large vibrations based on the instantaneous value, but with this invention, In this case, since the average value is determined, there is no possibility of erroneous detection by determining that the vibration is small. It is clear that if vibration actually occurs, it can be detected correctly because the axis itself will have a motion average vibration value. Furthermore, since scratches on the shaft do not cause false detection, shaft machining can be done more roughly than before, and the cost of shaft machining is reduced. Furthermore, if a computer is used to realize this device, as shown in 12 in FIG. 2, the average value of the vibration output can be recorded, so that changes over time can be known.

In the above explanation, the tachometer 13 is used as the standard time as the calculation devices 9a, 9b, 9c for calculating the average vibration value, but a fixed interval of time may be used as the standard time. Further, reference value setting devices 10a, 10b, 1
Although it is shown as a constant value as 0c, it is known that the vibration of a rotating body changes depending on the rotation speed, so the output of the tachometer 13 is introduced into the setting device, and the standard setting value is determined depending on the rotation speed. may be changed. Further, the reference value may be set not only one but a plurality of values; for example, one value may be set for an alarm and another value may be set for stopping the rotating body.

As described above, according to the present invention, the magnitude of vibration is determined not from an instantaneous value but from an average value of vibration detection values of the rotating body and the rotating body case during a predetermined period regarding the rotation of the rotating body and a predetermined value. Since the structure is configured to judge the vibration status of the rotating body by comparing it with It can be constructed at low cost since it can utilize equipment installed in In addition, since the vibration detection method is good even if there are some scratches on the shaft, it is possible to reduce the grade of shaft machining.
A highly accurate vibration detection method can be obtained at low cost.

[Brief explanation of the drawing]

FIG. 1 shows a conventional vibration detection method, and FIG. 2 is a configuration diagram showing an embodiment of a vibration detection device according to the present invention. In the figure, 1 is the rotating shaft of the rotating body, 2 is the case of the rotating body, 3 is a vibration detection device that houses the pick-ups 4 and 5, 6a and 6b are high frequency oscillators, 7 is an adder, 9a, 9b, 9c is a calculation device for calculating the average vibration value; 10a, 10b, and 10c are reference value setting devices; and 11a, 11b, and 11c are comparison devices. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A pick-up that outputs an output in response to each vibration in a rotating body and a case of this rotating body. A calculation device for calculating each average vibration value, and a reference value setting device for determining the magnitude of the vibration values of the rotating body and the rotating body case, and the output of the calculation device is larger or smaller than the output of the reference value setting device. A vibration detection device characterized in that it determines the vibration status of a rotating body based on the vibration condition. 2. A patent claim characterized in that the calculation device for calculating the average value is configured to calculate the average value within a fixed period of time, or to calculate the average value during the rotation period of a rotating body. The vibration detection device according to scope 1. 3. The vibration detection device according to claim 1, characterized in that the reference value setting device changes the set value according to the rotational speed of a rotating body.