JP2573336B2 - Bearing abnormality detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a bearing device for a rotary machine, and in particular, accurately grasps a state of forming a lubricating fluid oil film on a stationary plate to determine an abnormality of a bearing. The present invention relates to a bearing abnormality detection device that can be detected at an initial stage.

(Prior Art) In recent years, the scale of plants in the general industry has been steadily increasing, and as a result, the size of rotating machines has increased and the number of devices has also increased. Accordingly, since high reliability is required in such a rotating machine, it is necessary to reliably perform maintenance and inspection to prevent an accident.
In particular, an abnormality of the thrust bearing, which is likely to cause an accident in the rotating machine, has a great influence on others, so that its maintenance must be performed more reliably.

By the way, although the thrust bearing in the conventional rotary machine is an important element, its monitoring method is extremely insufficient. That is, as a conventional monitoring method of the thrust bearing, a method of measuring the temperature of the stationary plate, a method of measuring the vibration of the shaft system, or a method of scientifically analyzing the lubricating fluid has been adopted. These monitoring methods have the inconvenience that the thrust bearing is damaged and cannot be detected unless the thrust bearing has progressed considerably, and in many cases, it has already developed into a bearing accident at the stage of detecting an abnormality.
When a bearing accident occurs, it takes a long time to recover the bearing, and during that time, the rotating machine is stopped, so that the operation rate is reduced, which is a bottleneck for improving productivity. Especially,
Damage to the thrust bearing in a large-capacity turbine generator results in a very large loss of rotating machinery. Therefore,
It is very important to detect when an abnormal condition or initial damage has occurred in such a thrust bearing before it develops into a large bearing accident, and to take necessary measures.

As a generally used high-load thrust bearing device, a thrust bearing using oil as a lubricating fluid is most often used. In this type of bearing, an oil film is formed between the stationary plates by viscous effect of the oil on the sliding surface of the rotating shaft during operation of the vertical rotating machine to prevent direct contact between the rotating shaft and the stationary plate. doing.

However, when the slip surface is damaged due to poor assembly of the shaft system, overloading, inclusion of foreign matter, cavitation, or the like, it becomes difficult to form an oil film between the stationary plate and the rotating shaft. In other words, the oil film becomes very thin, and eventually the oil film breaks, leading to a bearing accident. Before the oil film breaks, the above-described monitoring method using the bearing temperature measurement method or the like has a problem in that the response to an oil film change is very insensitive. On the other hand, recently, as a method for directly monitoring the oil film thickness and the oil film pressure of the thrust bearing, a monitoring device in which a sensor for detecting them is installed on a stationary plate has been proposed. These monitoring methods can detect an abnormality at a much earlier stage than a monitoring method of bearing temperature or the like.

FIG. 5 is a configuration diagram showing an example of an oil film thickness measurement sensor. This oil film thickness measurement sensor includes an oscillator 1, a carrier high frequency from the oscillator 1 is amplified by an amplifier 2, and a high-frequency current flows through a resistor 3, a capacitor 4, and a coil 5 connected to a parallel circuit. The coil 5 is embedded in the stationary plate 6, and the mutual inductance related to the magnetic permeability of the material of the rotating plate 7 provided opposed thereto is measured by measuring the electric signal output from the demodulator 8 to indirectly control the oil film thickness δ. Can be measured. This oil film thickness measurement sensor can accurately measure the oil film thickness δ with almost no influence of the temperature drift of the oil film.

Further, in addition to the oil film thickness measuring sensor, a bearing temperature sensor including a thermocouple or a resistance thermometer, and an oil film pressure sensor including a pressure sensor using a semiconductor have been developed and used.

(Problems to be Solved by the Invention) The bearing abnormality detecting device including the oil film thickness measuring sensor, the bearing temperature sensor, and the oil film pressure sensor is complicated and expensive.

On the other hand, according to the bearing temperature monitoring device based on the conventionally used bearing temperature measurement method, it is difficult to detect an abnormality of the bearing at an early stage. It is a phenomenon that the bearing temperature rises due to the bearing abnormality.This is a phenomenon that occurs as a result of the bearing abnormality.However, the bearing temperature rises after the bearing abnormality occurs, and the temperature change is monitored by the monitoring device. This is because it takes time to reach the temperature sensor, and the speed at which the oil film can be detected is slower than when detecting changes in the oil film thickness or oil film pressure of the bearing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a bearing abnormality detection device that is easy and inexpensive, and that can detect a bearing abnormality very early.

[Configuration of the invention]

(Means for Solving the Problems) A bearing abnormality detection device according to the present invention is a bearing abnormality detection device that detects an abnormality of a bearing that supports a rotating shaft of a rotary machine, and is connected to an amplifier that amplifies a current from an oscillator. A pair of resistors, a capacitor, and a coil are connected to the parallel circuit, and the pair of coils are disposed before and after the bearing slide surface, while the current of the parallel circuit is changed due to a change in impedance of the preceding coil. An amplifier for detecting the fluctuation and a demodulator for outputting the fluctuation of the current are provided.

(Operation) When an abnormality occurs in the bearing and the oil film temperature on the sliding surface of the bearing changes suddenly, the impedance of the front coil close to the oil film changes suddenly. In this case, there is a difference in impedance between the front coil and the rear coil because it takes time to conduct heat due to a sudden change in oil film temperature. When an impedance difference occurs between the front coil and the rear coil, a change in current is detected by the amplifier, and the electrical output from the demodulator changes suddenly. An abrupt change in the electrical output of the demodulator enables early detection of bearing abnormality.

Embodiment An embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 2 is a sectional view showing a thrust bearing device of a large vertical rotating machine provided with one embodiment of the bearing abnormality detecting device according to the present invention. In FIG. 2, for example, the rotating shaft of a turbine generator
A cylindrical thrust collar 12 is attached to 11 by a cylinder key. A side surface of the thrust collar 12 is guided by a guide bearing 13, and a rotating plate 14 is mounted and fixed on a bottom surface by bolts or the like.

On the other hand, a plurality of fan-shaped stationary plates 15 are radially arranged to face the rotating plate 14 in the axial direction of the rotating shaft 11. These stationary plates 15 are supported by a spring table 18 provided at the bottom of a bearing oil tank 17 via a number of coil springs 16. The rotating plate 14, the stationary plate 15, the coil spring 16 and the spring base 18 are housed in a bearing oil tank 17, which is filled with oil 19, and the oil 19 is cooled by a number of oil cooling tubes 20. And rotating plate 14
And between the stationary plate 15 to perform a lubricating action.

The sensor part of the bearing abnormality detecting device is disposed at the position indicated by reference numeral 21 in FIG. 3, and the other part is the automatic monitoring circuit shown in FIG.
Housed in 22.

FIG. 1 is a configuration diagram showing a configuration of a bearing abnormality detection device. The bearing abnormality detecting device is provided with an oscillator 25 for generating a high-frequency current, and an amplifier 26 for amplifying the high-frequency current is connected to the oscillator 25. A parallel circuit 27 is connected to the amplifier 26, and a pair of resistors 28a and 28b, capacitors 29a and 29b, and coils 30a and 30b are connected in series to the parallel circuit 27.

The pair of coils 30a and 30b have a function as a sensor unit, and are installed on the stationary plate 15. The pair of coils 30a, 30b are disposed between the rotating plate 14 and the stationary plate 15, that is, offset in the front-back direction with respect to the bearing slip surface (hereinafter, the coil closer to the bearing slip surface is referred to as the front coil 30b, The coil on the far side is called the rear coil 30a).

Between the pair of capacitors 29a and 29b, and the front coil 30
A wire is connected between b and the rear coil 30a, and this wire is grounded. An amplifier is provided between the pair of resistors 28a and 28b.
The amplifier 31 is connected to the ground and the demodulator 32 is connected. The demodulator 32 is connected in parallel to the parallel circuit 27, and outputs a change in impedance of the front coil 30b as an electrical output. As shown in FIGS. 2 and 3, a bearing oil film pressure sensor 33, a bearing oil film thickness sensor 34, and an oil tank oil temperature sensor 35 are connected to the automatic monitoring circuit 22, and these sensors are used in combination. You may.

 Next, the operation of the above embodiment will be described.

When a bearing abnormality occurs and the oil film temperature on the bearing slip surface changes suddenly, the impedance of the front coil 30b close to the oil film changes suddenly. In this case, since it takes time for heat conduction due to a sudden change in oil film temperature, the impedance of the rear coil 30a does not change yet, and the current of the parallel circuit 27 fluctuates due to the difference in impedance between the front coil 30b and the rear coil 30a. The fluctuation of the current is detected by the amplifier 31, and the demodulator 32 outputs it as an electric output.

FIG. 4 is a characteristic diagram showing a change in the electric output of the demodulator 32 when the oil film temperature of the minute gap δ is changed. Normally, when the temperature of the oil film changes, the oil film thickness also changes, and the bearing minute gap δ also changes, but in FIG. 4, if the minute gap δ does not change and the oil film temperature changes during this period, the change in the electrical output will Show. According to FIG. 4, when the oil film temperature rises, the electric output drops sharply, and conversely, when the oil film temperature decreases, the electric output sharply rises sharply.

In addition, when a normal bearing abnormality occurs, both the bearing minute gap δ and the oil film temperature on the bearing slip surface change,
Coil 30a, 30b, capacitor 29a, 29b, resistor 28a, 28b
By changing the values and combinations of the above, the rapid change of the oil film temperature can be more greatly reflected on the electric signal.

As described above, according to the above-described embodiment, the abnormality of the bearing can be detected very early by the extremely simple and inexpensive device.

In the above embodiment, the case where the thrust bearing device of the large vertical rotating machine is provided with the bearing abnormality detecting device is described. However, the present invention is not limited to this, and the guide bearing device or the bearing of the horizontal shaft journal bearing device is not limited thereto. Can be applied to the abnormality detection. In addition to the detection of the temperature of the oil film of the bearing, the present invention can also be used for the purpose of reliably and immediately detecting a corresponding change in temperature.

〔The invention's effect〕

The bearing abnormality detection device according to the present invention is configured such that a pair of resistors, a capacitor, and a coil are connected to a parallel circuit connected to an amplifier that amplifies a current from an oscillator, and the pair of coils are arranged before and after with respect to a bearing slip surface. On the other hand, an amplifier that detects a change in the current of the parallel circuit due to a change in the impedance of the previous coil and a demodulator that outputs the change in the current are provided. An abnormality of the bearing can be detected very early, and a bearing accident can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a bearing abnormality detecting device according to the present invention, FIG. 2 is a sectional view showing a thrust bearing device of a large vertical rotating machine provided with the above embodiment, and FIG. FIG. 4 is a characteristic diagram showing the operation of the above embodiment, and FIG. 5 is a configuration diagram showing an example of an oil film thickness measuring sensor. 14 ... rotating plate, 15 ... stationary plate, 25 ... oscillator, 26 ... amplifier, 27 ... parallel circuit, 28a, 28b ... resistor, 29a, 29b
... condenser, 30a ... rear coil, 30b ... front coil,
31 ... amplifier, 32 ... demodulator.

Claims (1)

(57) [Claims] In a bearing abnormality detecting device for detecting an abnormality of a bearing supporting a rotating shaft of a rotary machine, a pair of resistors, a capacitor and a coil are provided in a parallel circuit connected to an amplifier for amplifying a current from an oscillator. The pair of coils are disposed before and after the bearing slip surface, and an amplifier that detects a change in the current of the parallel circuit due to a change in the impedance of the front coil and outputs the change in the current. A bearing abnormality detection device comprising a demodulator.