JPS6112596B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a failure alarm system for mechanical equipment including rotating parts. Machines and appliances that have rotating parts such as gears and bearings may have eccentricity of the inner ring, spots, scratches, etc.
When failures such as inner surface waving or spot scratches on the outer ring, uneven diameters of rolling elements, or waving occur, discovering this at an early stage is extremely important from the viewpoint of maintenance management, safety, and economics of machinery and equipment. is important. Furthermore, if it becomes possible to know not only the occurrence of a failure and issue an alarm, but also the type of failure, there is an advantage that countermeasures can be taken quickly. The present invention was made in order to solve such problems, and it converts vibrations generated in mechanical equipment equipped with rotating parts into electrical signals, detects the signals, and then performs frequency analysis. The present invention provides a failure alarm device that detects failures and issues warnings by extracting only vibrations caused by failures and measuring voltage levels, and also allows the type of failure to be known. The failure alarm device according to the present invention is constructed based on the following principle. Firstly, since the rotating part in which the failure has occurred causes vibrations at a specific frequency corresponding to its type, it is important to check the presence or absence of waves at such frequencies (hereinafter referred to as "specific frequencies") and their vibrations. By measuring the strength (hereinafter referred to as "level") of the failure, it is possible to detect the presence or absence of a failure and the extent of the failure. The shaft rotation speed is now 53.78Hz with the outer ring fixed.
(3227 rpm), number of balls: 14, contact angle α = 5 to 10°, revolution diameter of ball 101 D = 77.5 mmφ, ball diameter d = 10.32 mm
Taking the φ bearing 100 (see FIG. 1) as an example, the above will be explained in detail as follows. In other words, if the fundamental frequency of shaft rotation is fr, then from the perspective of vibration theory, the fundamental frequency of contact between inner ring rolling elements is fi,
The rolling element revolution fundamental frequency f ₀ and the rolling element rotation fundamental frequency f _b are expressed by the following formulas, respectively. f _i =1/2f _r (1+d/Dcosα) f ₀ =1/2f _r (1-d/Dcosα) f _b =Df _r /2d{1-(d/Dcosα) ² } The shaft rotation fundamental frequency f _r is Matches the shaft rotation speed,
Since the frequency is 53.78Hz, the above three frequencies f _i , f ₀ , and f _b are calculated as f _i =30.42 to 30.46, f ₀ =23.32, respectively.
~23.36, f _b =198.39 ~ 198.46. It is also known from vibration science that the specific frequencies corresponding to the types of failures in the inner ring, outer ring, and rolling elements are expressed as shown in Table 1 below, so the specific frequency calculation values for various failures are shown in Table 1 below. It will look like the right column.

[Table] Next, the second principle of the above principle is that the vibration waves generated in the rotating part use the natural vibration high frequency due to metal contact during rotation as the carrier wave, and the low frequency vibration caused by the occurrence of a failure is used as the signal wave (modulated wave ) is considered as an amplitude modulated wave. All of the specific frequency waves associated with the various failures described above are considered to be such signal waves. Even if this amplitude modulated wave is frequency-analyzed as it is, the signal wave of a specific frequency generated by a failure cannot be extracted. In order to extract this, it is sufficient to first detect the output from the vibratory electric signal converter and then perform frequency analysis on it. This makes it possible to know not only the occurrence of a failure, but also its type. However, if a failure alarm device is constructed based only on the principles described above, the following disadvantages will occur. In other words, when a large load is applied to a mechanical device that has rotating parts, for example, when the machine is a rolling mill and a material to be rolled is caught in it, extremely large vibrations occur. This occurs frequently, and since this vibration includes a low frequency similar to the vibration that accompanies the occurrence of the failure described above, it is inconvenient that an alarm is issued every time such a large load is applied. . In order to eliminate such inconveniences, the present invention adopts the third principle of eliminating the above-mentioned malfunctions by dividing the level of the detected specific frequency by the level of the entire vibration generated in the rotating part. And here it is completed. Hereinafter, the present invention will be explained in detail based on drawings showing embodiments thereof. In FIG. 2, reference numeral 1 denotes a vibrating electric signal converter such as a pickup that converts vibrations generated in an object such as a machine or appliance requiring an alarm into an electric signal. Note that a high-pass filter may be provided after the converter 1 to block low-frequency noise of 1 KHz or less. 2 is an overall level detection circuit that detects the average level of the entire output from the vibrating electric signal converter. 3 is a detection circuit. As described above, this circuit is a preprocessing circuit for detecting the presence or absence of a specific frequency wave due to a failure and its level. Reference numeral 4 denotes a specific frequency level detection circuit, which is constructed as follows in this embodiment. That is, in Figure 3, 4
Reference numeral 1 denotes a local oscillation circuit that oscillates a wave having a frequency that is the same as or similar to a specific frequency (single or plural) specific to the fault to be detected. If it is necessary to investigate multiple types of failures, use this local oscillator circuit 41.
uses a built-in timer to oscillate a frequency wave that changes continuously or stepwise within a certain range, such as 2 to 1000 Hz, at fixed time intervals such as every 5 minutes, and repeats it. 42 is a multiplication circuit that multiplies the output from the detection circuit 3 and the output from the local oscillation circuit 41. This circuit 42 has an amplitude modulation function.
In this embodiment, only one multiplier circuit is provided, but this is divided into two, and two types of circuits having a phase difference of 90° are provided from the local oscillation circuit 41 to these multiplier circuits (not shown). It is also possible to improve level detection accuracy by simultaneously outputting frequency waves, multiplying them by the output from the detection circuit 3 in each multiplier circuit, and taking the square root of the sum of the squares of each output and equally averaging them. be. Therefore, as is well known in amplitude modulation theory, when a specific frequency is included in the output from the vibratory electric signal converter 1, the oscillation frequency from the local oscillation circuit 41 matches the specific frequency. In this case, the output of the multiplier circuit 42 will include an extremely low frequency component having a level corresponding to the level of the specific frequency wave. 43 is a low-pass filter circuit for extracting the extremely low frequency component, and its output corresponds to the level of the specific frequency. Therefore, when there is a failure in the rotating part of a mechanical device, when the local oscillation circuit 41 outputs a frequency wave that is the same as or close to the specific frequency unique to the failure, the low-pass filter circuit 43 will identify the failure. A signal with a value corresponding to the frequency level is output. 44 is an integrating circuit, and even if dust or the like is temporarily trapped in the rotating part, the low-pass filter circuit 43
Since the output is generated from the low-pass filter circuit 4
By integrating the output of No. 3, the influence of the dust etc. on the output during non-failure is reduced. That is, in this way, the low-pass filter circuit 4 is not temporarily, but at least for a certain period of time.
If the output does not continue to occur from 3, it will not reach the value at which an alarm, which will be described later, should be issued. Therefore, an extremely short-term output due to dust or the like will not cause an alarm to be issued. Needless to say, this integral value is cleared each time the oscillation frequency from the local oscillation circuit 41 changes. Note that this integrating circuit may be removed. It goes without saying that the specific frequency level detection circuit 4 may be replaced with a bandpass filter or other frequency analysis means.
Bandpass filters are difficult to obtain with high accuracy, and the number of bandpass filters required depends on the type of failure, and other frequency analyzers are also expensive, so they are not suitable for use as the specific frequency level detection circuit 4. It is best to configure it as in the above embodiment. 5 is a division circuit for dividing the output value from the specific frequency level detection circuit by the output value from the overall level detection circuit 2; When the load fluctuates greatly, the resulting vibration causes an extremely large output to be generated from the integrating circuit 44.
If this output level is directly compared with a preset value (alarm generation reference value), there is a possibility that an alarm will be issued even though there is no actual failure. However, in the present invention, as described above, the output value from the integrating circuit 44 is divided by the overall average level, so when the load fluctuates greatly, the overall level also increases at the same time. The output will never increase. In fact, it will be smaller than normal.
6 is a judgment circuit, and an alarm reference value setting circuit 61
and an alarm command circuit 62. This alarm reference value setting circuit 61 outputs an alarm reference value that serves as a reference for determining whether or not the failure is of such a degree that an alarm should be issued. As a matter of course, the alarm reference value differs depending on the type of failure, so in synchronization with the oscillation of a frequency wave from the local oscillation circuit 41 that corresponds to a specific frequency specific to each failure, the circuit 61 outputs a Necessary alarm reference values are output in sequence. a is the synchronization command signal mentioned above. An alarm command circuit 62 compares the output from the division circuit 5 and the output from the alarm reference value setting circuit 61, and outputs an alarm command when the former value exceeds the latter value. 7 is an alarm circuit that issues an alarm based on an alarm command from the alarm command circuit. If it is necessary to also display what kind of failure it is, a failure part display that matches the currently oscillated frequency is displayed. The synchronization command is issued by the signal a from the local oscillation circuit 41.
Further, the alarm can be continued using a hold circuit or the like. As detailed above, according to the present invention, even if there is a large load change such as jamming of the rolled material, no unnecessary alarm will be issued due to this. Furthermore, it is extremely convenient because it is possible to know what type of failure is occurring if necessary. The alarm device of the present invention has the advantage that it can always alert not only to abnormal vibrations caused by a failure, but also to abnormal vibrations caused by liquid leakage, pipe drawing, etc.

[Brief explanation of drawings]

FIG. 1 is a simplified sectional view of the bearing, FIG. 2 is a block diagram of the entire invention, and FIG. 3 is a block diagram of a specific frequency level detection circuit. DESCRIPTION OF SYMBOLS 1... Vibratory electric signal detector, 2... Overall level detection circuit, 3... Detection circuit, 4... Specific frequency level detection circuit, 5... Division circuit, 6... Judgment circuit, 7... Alarm circuit.

Claims (1)

[Scope of Claims] 1. A vibrating electrical signal converter that is installed in an object that requires an abnormal vibration alarm, such as a machine or a device that has a rotating part, and that converts vibrations generated in this object into an electrical signal; a detection circuit that detects a signal; a specific frequency level detection circuit that detects or integrates the level of a specific frequency (single or plural) contained in the output of the detection circuit;
an overall level detection circuit that detects the overall level of the output of the vibratory electric signal converter; a division circuit that divides the output value of the specific frequency level detection circuit by the output value of the overall level detection circuit; and an output of the division circuit. It includes a judgment circuit that judges whether the value is a preset value that requires issuing an alarm, and an alarm circuit that issues an alarm along with a display or only issues an alarm based on the output of this judgment circuit. Become,
Failure alarm device for equipment with rotating parts. 2. The specific frequency level detection circuit includes a local oscillation circuit that oscillates a wave with a frequency that is the same as or similar to the specific frequency (single or plural) to be detected, and multiplies the output of the detection circuit and the output of the local oscillation circuit. a multiplier circuit that extracts extremely low frequency components contained in the output of the multiplier circuit and outputs a signal having a value corresponding to the specific frequency level; 2. A failure alarm device for equipment equipped with a rotating part according to claim 1, characterized by comprising an integrating circuit that performs integration.