RU2659101C1 - Method for determining the friction moment in rotating bearings - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention relates to machine building, namely, to bearing industry, and can be used for receiving testing of rotating bearings. By method of determining frictional moment in rotating bearings, an analogue function of running-out is detected, two identical conjugate time intervals are selected on this function, the number of phase segments of the rotation angle passed over each time interval is counted. Required parameter is proportional to difference in the number of phase parts at the first and second time intervals.

EFFECT: technical result consists in reducing hardware costs and laboriousness of detecting the desired parameter.

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Description

The invention relates to mechanical engineering, namely the bearing industry, and is intended to assess the quality of bearings by the magnitude of the friction moment.

The quality of bearings largely determines the quality of machines and mechanisms. The quality assessment of bearings is carried out by conducting tests - research, acceptance tests from the manufacturer, customer receptions.

In the tests, specialized friction machines are used (patent RU 2336917, publ. 10.09.2009; patent RU 2369852, publ. 10.10.2009). Define certain test conditions (patent RU 2504701, publ. 01.20.2014). To assess the quality of bearings, various parameters are measured, for example, an electric current flowing through a bearing (patent RU 2529644, publ. 09.27.2014). More informative are methods using vibrational effects (patent RU 2407999, publ. 12/27/2010). However, the known methods and their practical implementation involve significant hardware costs and the complexity of identifying the desired parameter.

As a prototype, a method for detecting and automatically identifying damage to rolling bearings according to patent RU 2470280 IPC G01M 13/04, publ. 12/20/2012. In accordance with this method, the vibrations of a working bearing, measured in the form of a timing diagram of an analog signal, are converted into digital data. Next, the primary transformation is filtered using a binary vector, which is determined during the following operations: two adjacent source vector intervals, one of which is the reference interval, are selected on the previously filtered time diagram of the processed signal, and the signals present in the control and reference intervals are subjected to multiple filtering, as a result of which, after each filtering, the likelihood ratios of shock pulses are calculated, defined as The ratio of the rms values of the filtered signal present in the control interval to the rms values of the filtered signal present in the reference interval compares the calculated likelihood ratios with a preset threshold value and estimates the probability of occurrence of a shock pulse in the first control interval, information about the appearance of a shock pulse in the test interval are written as the source elements of the binary vector, and then all The binary vector elements for all subsequent control and reference intervals, which are selected interactively, with an offset in a specific direction, and the mentioned binary vector elements take a value of 1 in the region where the shock pulse appears and 0 in the region in which the shock pulse does not appear.

The method under consideration has the same disadvantages as its analogues. In addition, the presence of shock phenomena in bearings is their private property. Any defects appear as a moment of resistance to rotation, i.e. friction moment. The moment of friction in the bearing is an integral parameter of its quality.

The technical result of the invention is to reduce hardware costs and the complexity of identifying the desired parameter.

The tasks are solved:

1. Development of a high-performance method for determining the moment of friction in bearings, which gives an integral characteristic of quality and assumes low hardware costs for its implementation.

2. Development of an example implementation of the proposed method for determining the moment of friction in rolling bearings.

3. The rationale for technical decisions.

This result is achieved by the fact that in accordance with the proposed method for determining the moment of friction in rolling bearings, in which the time diagram of the analog signal of the working bearing is detected, it is converted into digital data, while the time diagram is obtained in the form of stick out functions, two identical ones are selected on the time diagram conjugate time intervals, count the number of passed phase parts of the angle of rotation at each time interval and determine the moment of friction in the bearing according to the formula

,

,

where J is the moment of inertia of the rotating parts;

Δt is the time interval;

ϕ _W - phase part;

n ₁ , n ₂ - the number of phase parts, respectively, in the first and second time intervals.

The essence of the proposed method for determining the moment of friction is as follows.

For given experimental conditions (radial and main load, temperature, external electric, magnetic and radiation fields, etc.), rotation of one bearing ring relative to another is provided.

. Этот процесс отражается функцией выбегаConsider free rotation starting from a certain speed

. This process is reflected by the coast function.

- мгновенное значение частоты вращения.Where

- instantaneous speed value.

The stick-out function (1) is non-linear, but since the viscous friction in the bearing is small with respect to constant (Coulomb) friction, then in a limited area of 1-2 (see Fig. 1) this function can be approximated by a straight line segment. Then the friction moment M _Tr in the bearing is determined

where W ₁₂ - energy consumption for friction;

ϕ ₁₂ is the increment of the phase (angle of rotation). Energy consumption for overcoming friction can be found through kinetic energy

where J is the moment of inertia of the rotating parts;

- мгновенное значение частоты вращения соответственно в моменты времени t₁ и t₂.

- the instantaneous value of the rotational speed, respectively, at time t ₁ and t ₂ .

и

обратимся к дискретному методу. Заметим, что дискретный метод преобразования позволяет получить более высокую точность и надежность по сравнению с аналоговым методом. Для реализации дискретного метода разделим полный угол поворота (2π) на N равных фазовых частей (шагов) - ϕ_ш To find the instantaneous speed values

and

turn to the discrete method. Note that the discrete conversion method allows to obtain higher accuracy and reliability compared to the analog method. To implement the discrete method, we divide the total angle of rotation (2π) into N equal phase parts (steps) - ϕ _w

In the vicinity of time t _1, we choose a symmetric interval Δt ₁ from time t _1H to time t ₁₂ . Similarly, for time t ₂ - the interval Δt ₂ from time t ₁₂ to t _2K . Thus, the boundaries of the intervals Δt ₁ and Δt _{2 are} combined. Additionally, we accept the condition

Since the rotation angle in time Δt is equal to the number of phase parts passed, we obtain

where n ₁ , n ₂ - the number of phase parts, respectively, for the time Δt ₁ and Δt ₂ .

Taking into account formulas (3), (6), we obtain

The phase increment in the time interval t _1-2 = Δt taking into account the linear approximation and condition (5) will be

Based on formulas (7), (8), formula (2) takes the form

является константой испытательной установки, реализующей предлагаемый способ определения момента трения в подшипниках.Value

is a constant test installation that implements the proposed method for determining the moment of friction in bearings.

Consider the implementation of the proposed method for determining the moment of friction in rolling bearings in relation to acceptance tests. In the context of mass production, the manufacturer conducts full-size tests of bearings on a sample from the batch. To avoid getting into a responsible product, the consumer checks the quality of each bearing according to a simplified method and conducts acceptable tests.

The installation device is illustrated by drawings:

FIG. 1 - design scheme;

FIG. 2 - structural diagram of the electromechanical part;

FIG. 3 is a view A of FIG. 2;

FIG. 4 is a functional diagram of an electronic unit.

Accepted Designations

1. Case

2. Bearing bracket

3. Test Bearing

4. Electric motor

5. Friction clutch

6. clutch lever

7. Lever axis

8. Electromagnet

9. Lever spring

10. Friction pad

11. Bracket sleeve

12. The screws of the sleeve 11

13. Central hub

14. Phase sensor disc

15. Tooth area of the disc 14

16. Disc screws 14

17. Permanent magnet

18. Pole lugs

19. Electric coil

20. Power supply

21. Control toggle switch

22. Mode switch (batch)

23. Phase sensor signal conditioner

24. Reset Signal Conditioner

25. Reference frequency generator

26. The conjuncture of the time chain

27. Time counter

28. Time chain decoder

29. RS-trigger time chain

30. Reversible counter

31. Reversible counter decoder

32. Indicator

33. RS-trigger time interval Δt ₁

34. Trigger Disjunctor 33

35. RS-trigger time interval Δt ₂

36. Trigger Disjunctor 35

37. Market Records

38. Subtraction

In the housing 1 of the electromechanical part, the bracket 2 of the test bearing 3 is fixed, an electric motor 4 having a friction clutch 5 on the cantilever key part of the shaft. It is advisable to use a direct current motor with parallel excitation as an electric motor. In this case, its speed is proportional to the supply voltage, which leads to a linear scale of the speed control on the power supply. The electric motor can be equipped with a tachometer. The clutch has a drive comprising a rotary lever 6 with an axis of rotation 7 and an electromagnet 8. The initial position of the lever is realized by a spring 9. The clutch on the working end surface has a friction lining 10 in the form of a ring.

The test bearing is mounted on its outer ring in the bracket 2 by means of a sleeve 11, which is fixed with knurled screws 12. The coupling of the outer ring of the bearing with the sleeve is carried out with some interference, and the coupling of the sleeve with the bracket with a clearance. The inner ring of the test bearing is connected with an interference fit with the central sleeve 13 having an axial threaded hole for interaction with the puller. The right end surface of the central sleeve (drawing orientation) is designed to interact with the coupling, and the left - to mount the phase sensor.

The phase sensor is represented by a disk 14 of a magnetic material with a tooth zone 15. The phase sensor disk is mounted on the central sleeve 13 by means of thumb screws 16. The phase position of the disk 14 is converted to an electrical signal by a magnetoelectric converter, which is composed of a permanent magnet 17, two pole pieces 18 and an electric coil 19.

The presented design of the electromechanical part allows, due to a set of two bushings (11, 13) of the simplest form, to cover the range of sizes of consumer bearings.

Depending on the production conditions, a fiber-optic sensor can be used as a phase sensor (see Sharygin L.N., Katkova L.E. Designing of competitive technical products. - Vladimir: Transit-IKS publishing house, 2017. ISBN 978-5- 8311-1024-1. P. 346-355). For such a sensor, the phase part will be determined by the diameter of the optical fiber.

The electronic unit is designed to control the testing process and identify the desired parameter by the signals of the phase sensor. The controls are:

- a power supply 20, providing voltage E of the power supply of the microcircuits, a voltage of the electromagnet 8 and an adjustable voltage of the electric motor 4. The power supply contains a toggle switch "Network";

- the control toggle switch 21 into two positions: the "Mode" position with contacts S1, S2 and the "Measurement" position with contact S3;

- batch mode switch 22, which sets the nominal value of the speed

The electronic unit has two shapers:

- the driver 23 translates the pulses of the electric coil 19 of the phase sensor into a rectangular shape;

- shaper 24, creating a short pulse along the front of the voltage E by contact S3 - reset pulse.

, значит, зависимостью момента трения от частоты вращения. Шкала пакетного переключателя градуируется в номинальных значениях частоты вращения ϕ_и, а подключение выходных шин дешифратора осуществляется с соблюдением условия (5).The circuit that sets the time scale is presented to the reference frequency generators 25, three-input conjunctor 26, pulse counter 27 and decoder 28. The control element of the time circuit is trigger 29, which is set to a single state by a reset pulse from the output of the former 24. In the “Mode” control switch the conjunctor 26 passes the pulses of the generator 25 to the input of the counter 27, respectively, at the output of the decoder 28, the output buses are sequentially excited. Switch 22 broadcasts buses corresponding to time instants t _1H , t ₁₂ and t _2K . The pulse of the high bus m of the decoder puts the control trigger 29 in the zero state and the conjunctor 26 closes the pulses of the generator 25 to the input of the counter 27. The use of the packet switch 22 due to the nonlinearity of the run-out function

, hence, the dependence of the friction moment on the rotation frequency. The scale of the packet switch is graduated in the nominal values of the speed ϕ _and , and the output bus lines of the decoder are connected in compliance with condition (5).

To find the difference in the number of phase parts that have passed over the time Δt ₁ and Δt ₂ , a reversible counter 30 is used, the state of which is translated into a decimal code by the decoder 31 and reflected by the indicator 32. The time interval Δt ₁ is generated by the trigger 33, which is set to a single state by the pulse from the output switch 22 corresponding to time t _1H , and return to the zero state with pulse t ₁₂ through disjunctor 34. Similarly, trigger 35 generates a time interval Δt _{2 with} setting pulse t ₁₂ and reset pulse t _2K through the disjunctor 36. Trigger 33 opens the conjunctor 37 records of the reverse counter 30, and the trigger 35 opens the subtractor 38.

Operation of the unit for acceptance tests of bearings. The user mounts the test bearing 3: presses the bearing along the outer ring into the sleeve 11 of the bracket; presses the bearing along the inner ring onto the central sleeve 13; secures the resulting assembly unit with screws 12 in the bracket 2. Next, measure.

. Пакетным переключателем 22 задают номинальное значение частоты вращения

.Test conditions are specified. The regulator voltage of the electric motor 4 on the power unit 20 sets the maximum value of the speed

. Packet switch 22 set the nominal value of the speed

.

(определяют либо по тахометру, либо по времени - это единицы секунд) переводят тумблер управления 21 в положение «Измерение». Переброс тумблера управления обеспечит отключение электродвигателя и фрикционной муфты, а замыкание контакта S3 приведет к созданию формирователем 24 короткого импульса сброса. Этим импульсом все элементы памяти - триггеры 29, 33, 35 и счетчики 27, 30 - установятся в исходное положение. Одновременно контактом S3 открывается конъюктор 26, и импульсы генератора опорной частоты 25 начинают поступать на счетчик 27.Turn on the installation of the “Network” toggle switch on the power supply 20. Transfer the control toggle switch 21 to the “Mode” position. In this case, the electric motor is turned on by the contact S1, and the electromagnet 8 is turned on by the contact S2, which connects the friction clutch 5 with the central sleeve 13 using the lever 6.

(determined either by the tachometer or by time — these are units of seconds) the control switch 21 is moved to the “Measurement” position. The transfer of the control toggle switch will disable the electric motor and the friction clutch, and the closure of contact S3 will cause the driver 24 to create a short reset pulse. With this pulse, all memory elements - triggers 29, 33, 35 and counters 27, 30 - will be set to their original position. At the same time, the connector 26 opens with the contact S3, and the pulses of the reference frequency generator 25 begin to flow to the counter 27.

In the process of free rotation continues filling of the counter 27 of the time chain. When the time t _{1H is} reached, a pulse appears on the corresponding bus of the decoder 28, which, through the switch 22 at the input S, sets the trigger 33 to a single state. The transfer of this trigger leads to the opening of the junction 37, and the pulses of the phase sensor through the shaper 23 begin to fill in the reverse counter 30 at the summing input (+). This process will end with the appearance of the decoder pulse output 28 corresponding to time t ₁₂ . The specified pulse through the disjunctor 34 will return the trigger 33 to its original state.

At the same time t _{12, a} trigger 35 is triggered, which opens the connector 38, which leads to the arrival of pulses of the phase sensor to the subtracting input (-) of the reverse counter 30. The subtraction ends at time t _2K , when trigger 35 is reset through the disjunctor 36. Thus Thus, the difference between the number of pulses of the phase sensor that have passed during the time Δt ₁ and Δt ₂ will be recorded on the reversible counter 30. This value will be reflected on indicator 32. The desired parameter is determined by the formula (9). The operation of the electronic unit is completed by the appearance of a pulse on the senior bus m of the decoder 28 of the time chain. This pulse will return the trigger 29 to its original state, which will lead to the closure of the junction 26.

Note that part of the functions of the electronic unit and the calculation by formula (9) can be assigned to a computer.

Thus, the proposed method for determining the moment of friction in rolling bearings allows you to quickly identify the desired parameter with low labor costs. The implementation of the proposed method involves a fairly simple design solutions. The method can be applied to determine the moment of friction in rolling bearings during their experimental development.

Claims (6)

A method for determining the frictional moment in rolling bearings, in which a time diagram of an analog signal of a working bearing is detected, converted into digital data, characterized in that the time diagram is obtained as a stick out function, two identical conjugate time intervals are selected on the time diagram, and the number of passed phase parts of the angle of rotation at each time interval and determine the moment of friction in the bearing according to the formula

, where J is the moment of inertia of the rotating parts; Δt is the time interval; ϕ _W - phase part; n ₁ , n ₂ - the number of phase parts, respectively, in the first and second time intervals.

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