RU2502900C2 - Method of electrodynamic definition of operating parameters of metal-polymer friction pairs of drilling winch belt-shoe brakes - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: thermal-contact interaction of working surfaces between brake pulleys and friction lining generates electric currents governed by sine law of flat electromagnetic wave variation at glow and spark discharge modes. Operating parameters of friction pairs vary in time with different amplitudes described for specific loads by period π, period of dynamic friction factor 2-π, period of surface temperature at heating and forced cooling π/2, as well as solitons, i.e. pulses with different wavelengths of period π in contact gap of friction pairs, wear of pulley rim working surface and that of friction lining π.

EFFECT: possibility to define operating parameters of friction pairs.

10 dwg

Description

The invention relates to mechanical engineering and can be used in tape-shoe brakes of drill hoists.

, где δ_Н - толщина фрикционной накладки; R_Н - радиус нерабочей поверхности фрикционной накладки; и по данной формуле выполняют расчеты при условии, что материал накладки не достиг величины допустимого износа [1, аналог]. Однако не указано закономерности изменения эксплуатационных параметров металлополимерных пар трения ленточно-колодочного тормоза буровой лебедки.It is known that for a given design scheme of a tape-shoe brake with an even number of friction linings, which are fixedly mounted on an arc of a brake band around the working surface of the brake pulley, an angle β is determined that indicates the position of an arbitrary radius - vector ρ _i , relative to the abscissa axis, i.e. the touch point, and then the touch surface of the lining with a pulley, using the dependence of the form $$\sin \beta =\sqrt{\mathrm{one}/\left({\delta }_N+8\right)}$$

Where δ _h - the thickness of the friction lining; R _N is the radius of the idle surface of the friction lining; and according to this formula, calculations are performed provided that the lining material has not reached the allowable wear value [1, analogue]. However, the laws of the change in the operational parameters of metal-polymer friction pairs of the drawbar brake of the drawworks are not indicated.

It was found that the control of the load of friction pairs of the tape-shoe brake of drawworks is carried out both according to linear and non-linear laws of changing the frequency of rotation of the brake pulley depending on the braking time [2, prototype]. At the same time, it is not shown specifically according to which law the basic operational parameters of the friction tape brake shoe pairs will change.

The aim of the present invention is to develop a method for the electrodynamic establishment of patterns of change in the operational parameters of metal-polymer friction pairs of tape-shoe brakes of a drawworks.

This goal is achieved by the fact that during contact-thermal interaction of the working surfaces of brake pulleys and friction linings, electric currents are generated that obey the sinusoidal law of variation of a plane electromagnetic wave during smoldering and spark discharge modes, and at the same time, patterns of change in the operational parameters of friction pairs in time occur with various the amplitudes described for: specific loads period π; dynamic coefficient of friction with a period of 2π; surface temperatures during heating and forced cooling with a period of π / 2, as well as solitons (pulses) with different wavelengths with a period of π in the contact gap of friction pairs; wear of the working surface of the pulley rim and friction lining period π.

Compared with the analogue and prototype, the proposed method has the following distinctive features: electrodynamic establishment of patterns of change in the operational parameters of metal-polymer friction pairs of drawworks brake brakes of a drawworks allows you to have: maximums and minimums of change: specific loads; dynamic coefficients of friction; surface temperatures; wear and tear; which will make it possible to further manage their wear-friction properties.

In Fig.1, 2 are shown: the general kinematic diagram and its fragment of the tape-shoe brake of a drawworks, and in Fig.3 a cross-section along A-A of the friction brake assembly; legend: S _Н , S _С - tension of the running and running branches of the brake band; F _p - the force exerted by the worker to the brake control lever; ω is the angular speed of rotation of the pulley; r _W , r - radii: of the working surface of the pulley and crank of the crankshaft; 1-12 - numbering of friction linings; figure 4 shows the relationship between the sinusoidal law of change of a plane electromagnetic wave during smoldering and spark discharges, and the operational parameters of the brake friction pairs: b - the amplitude of the change in specific loads (p, MPa) [π]; a change in surface temperatures (t, ° C) during heating (1) and forced cooling (2) [π / 2]; the amplitudes of changes in wear (U, mm) of the drum rim (a) and friction lining (b) [π]; figure 5 illustrates the plot of the specific loads in the interaction of the serial lining of the tape with the working surface of the pulley at r _W <r _n ; legend: S _n ', S _c ' - the tension of the running and running sections of the branches of the brake band; F _ck - the friction force; δ is the length of the contact zone of friction pairs; b is the thickness of the lining; r _n is the radius of the working surface of the lining; f is the dynamic coefficient of friction; figure 6 shows the patterns of change over time (τ) of the dynamic coefficient of friction (f) for a metal-polymer friction pair (at p = 0.3 MPa, V = 0/6 m / s); 1,2 - high-frequency and low-frequency components of the "dry"friction; 3 - curve with "wet"friction; 4 - systematized sinusoidal curve; Fig. 7 shows the patterns of variation of the heating curves (experimental 1, 2 and calculated 1 ', 2') and natural cooling (experimental 1 ", 2" and calculated 1 ', 2'") during phase transformations in the surface layers of friction materials (a) FC-24 (1) and code 143 (2); Figs. 8 and 9 show soliton effects on the working surfaces of friction pads during the interaction of, respectively, two solitons traveling in the same direction and a coupled pair of solitons; legend: A, x - amplitude and wavelength; τ 'is the pulse time; figure 10 illustrates the patterns of linear wear (I _h ) of the working surfaces of the friction linings FK-24A with minimum and maximum specific loads (p) in the friction pairs of the brake depending on their surface temperature.

According to the kinematic scheme (see Fig. 1), the friction linings 3 are mounted on brake bands 2, which are attached to the balancer 11 at one end (from the side of the runaway branch II of the belt 11) and to the crank necks 6 from the side of the branch of the branch I) and 9 crankshaft.

Serial tape-shoe brakes of a drawworks operate as follows. By moving the handle 1, the crankshaft 10 is rotated, as a result of which the driller tightens the brake belts 2 with friction linings 3 and they sit on the brake pulleys 4. The braking process with a tape-block brake (see figure 2) is characterized by the following stages: initial (first) , intermediate (second) and final (third). Let us dwell on each of the stages separately.

At the initial stage of braking, the friction linings 3 located in the running part of the brake belt 2 interact with the working surface of the brake pulley 4. The front of interaction extends towards the friction linings 3 of the rolling branch (I) of the brake belt 2.

The intermediate stage of braking is characterized by the further spread of the interaction front towards the friction linings 3 of the runaway branch (II) of the brake belt 2.

The final stage of braking is characterized by the fact that almost all the fixed pads 3 of the brake belt 2 interact with the working surface of the rotating pulley 4. During braking, the sequence of friction surfaces coming into contact is repeated. The full braking cycle is completed by stopping the brake pulleys 4 with the drum 5. The control of the winch brake is also carried out by supplying compressed air through the driller's valve 7 to the pneumatic cylinder 8, the rod of which is connected to one of the crank crankshaft necks 10 of the brake. The pressure value of the compressed air in the pneumatic cylinder is regulated by turning the crane 7 of the driller.

When uneven wear of the friction linings 3 mounted on the belts 2, the balancer 11 at the time of braking slightly deviates from the horizontal position and evens the load on the runaway branch (II) of the brake belts 2, while ensuring uniform wear of their working surfaces.

A plane electromagnetic wave during smoldering and spark discharge modes, which occurs when an electric current is generated in the friction pairs of a tape brake shoe obeys the sinusoidal law of its change (see Fig. 4). The linear wear (I _h ) of the metallic (a) and non-metallic (b) friction elements is characterized by different amplitudes of their change with a period of π. The exact same relationship only for metal-polymer brake friction pairs is also true for the pattern of change in specific loads arising between them (see Fig. 5). As for the surface temperatures of the friction pairs and their forced cooling, curves 1 and 2 (see Fig. 4) are characterized by the same amplitude of their change with a period of π / 2.

The patterns of changes in the diagrams of specific loads and their values in friction pairs in relation to sliding speed and surface temperature affect:

- stress-strain state of materials under the action of normal force;

- stress-strain state caused by a change in the structure of the surface and near-surface layers of materials (defects);

- thermal stress-strain state of materials; the rate of change of the dynamic coefficient of friction, and as a consequence, the braking torque;

- the time of the cycles of destruction of surfaces and the average particle sizes that are exempted from them;

- generated forward and reverse currents during the interaction of contacting surfaces;

- the work function of the electrons from the metal friction element.

In the energy aspect, friction is the process of transforming the mechanical energy entering the system into electrical, thermal and other types of energy. The redistribution of energy flows on the surfaces of friction pairs of braking devices is observed only in the processes of friction itself, and therefore it is necessary to develop and use in-situ research methods.

The study over time of the dependences of the dynamic coefficient of friction of the friction assemblies of the brake devices (Fig. 6) allows us to state a dynamic picture of the overall balance of the energy supplied and allocated to the tribosystem.

External work applied to the tribosystem is spent on the elastic and plastic deformation of the surface layers and on the formation of microthermobatteries, which operate in microthermoelectric generators and microthermoelectric refrigerators, and as a result, direct heating and cooling of the surface and near-surface layers of friction pairs of brake devices. Other types of transformation of mechanical energy at low sliding speeds of the friction pairs of the brakes are insignificant (for example, radiation). The work of friction depends on the area of actual contact and on the physicomechanical and chemical properties of the surface and near-surface layers of materials of friction pairs of brake devices that harden and soften relatively slowly. Therefore, part of curve 2 (Fig. 6) of the dynamic coefficient of friction, which is described by the low-frequency component, is associated with the mechanical energy entering the tribosystem. The latter is spent on its redistribution and maintenance of the microthermal batteries, which generate electrical energy with its subsequent transformation into thermal energy in the surface layers of the elements of the friction assemblies of the brake devices.

The nature of the high-frequency component (curve 1 in Fig. 6), in our opinion, is related to the discreteness of the contact, and the high-frequency peaks of the dynamic friction coefficient correspond to instantly occurring energy processes in the contacting surface layers, which are a source of heat and cold, due to the generation of direct and reverse currents. Curves 1, 2, and 3 (Fig. 6) contain information on the influence of the direction of the current generated in the metal-polymer friction pairs on the value of the dynamic coefficient of friction. When direct microcurrents pass from the contacting surfaces of the rim of the brake pulley to the working surfaces of the friction linings (anode-polarized surfaces of the linings) f is always larger (see Fig. 6 time intervals (510-520) s and (550-570) s for curves 1 and 2) than at the cathode-polarized sections of the surface of the plates, the material of which is at temperatures above the permissible temperature, and in this case reverse microcurrents occur (see Fig. 6 time interval (510-580) s for curve 3). Moreover, in all cases / decreases with increasing current density j _n at the contact of the friction pairs of the brake devices. The dynamic coefficient of friction of the cathode-polarized sections of the friction linings is always less than the dynamic coefficient of friction of their anode-polarized sections, i.e. (f _a > f _k ), as j _n increases, it changes differently for different materials.

Figure 6 shows a systematized sinusoidal curve with the same amplitude with a period of 2π, which describes the high-frequency (curve 1) and low-frequency (curve 2) components of the "dry" friction.

Thus, the repolarization of the friction lining sections in the friction pairs of the brake devices causes inversion of microcurrents and a change in their values, and as a result, a change in the dynamic coefficient of friction characterizing the energy processes in their surface and near-surface layers of friction pairs.

The electric currents generated on the friction surface of the interacting metal-polymer friction pairs of the tape-shoe brake heat their surface layers and penetrate deep into them. Thus, the currents generated on the friction surface contribute to the appearance of surface temperature, and the heat penetrating deep into the friction pairs contributes to the development of volumetric temperature. The discharge currents arising during the interaction of friction pairs contribute to the development of flash points.

Figure 7 presents the patterns of changes in the heating and forced cooling curves during phase transformations in the surface layers of friction materials FK-24A (1) and code 143 (2), tested on a model tape-shoe brake under bench conditions. From the graphical dependencies shown in Fig.7, it follows that the surface temperature during heating and forced cooling of the friction pairs of the brake have the same amplitude with a period of π / 2.

The graphical dependences (see Fig. 7) show the heating curves during phase transformations in the surface layers of the friction materials of the codes ФК-24А and 143. The formaldehyde resin is used as a binder component in the first material, and rubber in the second.

It was found that the experimental temperatures (from 250 to 475 ° C) of the transformation effects are slightly lower than the calculated values in the time interval from 515 to 1050 s. The largest discrepancy between the calculated and experimental temperatures (up to 40 ° C) was observed for cipher material 143 when loading brake friction pairs for a duration of 750 s. The calculated and experimental values of the temperatures of natural cooling of the surface layers of these materials differ slightly.

During natural cooling, the presence of solitons (see Figs. 8 and 9) affects the condensed state of the elementary volumes of the surface layers of friction linings (which are at a temperature higher than that acceptable for their materials) structurally stable solitary waves in a nonlinear dispersive medium. Soliton behaves like particles. When interacting with each other or with some other disturbances (friction force), the solitons do not collapse, but diverge, keeping their structure unchanged. The soliton structure is maintained stationary due to the balance between the action of the nonlinear system and dispersion.

It was established that solitons can retain their structure for a long time in the presence of a slight attenuation or as a result of a smooth cylindrical curvature of the wave front in the space between the interacting friction pairs of the braking devices.

Solitons, like particles, can form bound states from two or more pulses (Figs. 8 and 9).

In a system of many solitons, a complex stochastic movement of particles in the space between the interacting friction pairs of brake devices occurs. According to Figs. 8 and 9, the solitons in the contact gap of the friction pairs of the brake propagate with different amplitudes having different wavelengths with a period π.

Patterns of linear wear (I _h , mm) of the working surfaces of the friction linings FK-24A at the minimum and maximum specific load (p) in the friction pairs of the band brake shoe of the U2-5-5 winch depending on their surface temperature (t) are illustrated in FIG. 10. From the latter it follows that with an increase in the surface temperature in the contact zone of the friction pairs of the brake, the linear wear of the working surface of the friction lining decreases. In this case, the wear of the working surface of the pulley rim and friction lining vary in different amplitudes with a period of π.

Thus, on the basis of electrodynamics, regularities have been established for changing the operational parameters of friction pairs of tape and shoe brakes of drawworks, varying with different amplitudes with a period from π / 2 to 2π.

Information sources

1. Pat. Russia 2357131 C2, cl. F16D 49/08 for 2009 [analogue].

2. Vinnitsky M.M. Rational management of hoisting operations / M.M. Vinnitsa. - M .: Nedra, 1978. - P.103-105 [prototype].

Claims (1)

A method for the electrodynamic determination of patterns of change in the operational parameters of metal-polymer friction pairs of tape winch brakes of a drill hoist containing a drum of a winch resting on a lifting shaft, brake pulleys are installed from the ends of the drum, the working surfaces of which surround the brake bands with friction linings installed on their bow arc with a uniform pitch , separated by spacer bars, while the ends of the runaway branches of the brake bands through rods attached to the balance ru, and the ends of the oncoming branches to the crank necks of the crankshaft, which is connected via a transmission device to the brake control lever, characterized in that during contact-thermal interaction of the working surfaces of the brake pulleys and friction linings, electric currents are generated that obey the sinusoidal law of variation of a plane electromagnetic wave under smoldering and spark discharge regimes, and at the same time, the patterns of change in the operational parameters of friction pairs in time occur with different amplitudes itodes described for: specific loads with a period of π, dynamic coefficient of friction with a period of 2π, surface temperatures during heating and forced cooling with a period of π / 2, and also solitons - pulses with different wavelengths with a period of π in the contact gap of friction pairs, wear of the working surface of the rim pulley and friction lining period π.

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