Patent Application
20240209894
The disclosure relates to slide bearings, specifically to methods for regulating the physical properties of the slide bearings in operation.
The further terminology and designations are used in accordance with GOST ISO 7902-1-2001, 18282-88.
The most important performance characteristics of a slide bearing are the related eccentricity ϵ, the related thickness of lubricant film ξ=1-ϵ associated with it, and the bearing modulus (Hersey number) c λ=ηωB/p. A stable performance of the slide bearing in the field of reliable hydrodynamic lubrication is possible with the values of 0.1 <ξ<0.3 and λ>λcr, at which a lubrication layer reliably separates the rotating parts of the bearing and at the same time preserves the vibrational resistance to self-oscillations of the shaft.
The terms bearing modulus and Hersey number are used interchangeably herein.
The existing theoretical methods for designing slide bearings are highly approximate and based on a large number of assumptions, in particular: (1) the lubricant conforms to a Newtonian liquid; (2) the geometry of the article ideally conforms to theoretical equations; (3) oscillations are insignificant; (4) the physical parameters of the lubricant (viscosity, pressure, layer thickness, etc.) are constant in the axial direction; (5) the dynamic viscosity is assumed to be a constant nefr in the entire range of operating temperatures; (6) reversible and irreversible changes in the viscosity are not taken into account; exact temperatures of the lubricant film, shaft, and bearing, which define the variation in the related clearance of the bearing as a function of temperature, are replaced with mean values of Teff; (7) roughness of friction surfaces are assumed to be unchanged; (8) the value of the friction coefficient is calculated by rough approximation of the Petrov and Vogelpohl formulas; (9) changes in rigidity and hardness of the surface of the shaft and the bearing are not taken into account; (10) the heat dissipation from the bearing to the surrounding environment is not taken into account.
In addition to these assumptions, the real properties of slide bearings vary significantly in the course of prolonged operation and deviate even more from the ideal ones.
In various implementations, a method of controlling a bearing modulus for a slide bearing is provided. A temperature dependence of the dynamic viscosity of a lubricant of the slide bearing is determined. A mixed-film lubrication to hydrodynamic lubrication transition temperature of the slide bearing is determined. The temperature dependence of the bearing modulus λ(T) and a value of the bearing modulus λcr of the mixed-film lubrication to hydrodynamic lubrication transition of the slide bearing is determined on the basis of the temperature dependence of the dynamic viscosity of the lubricant. An operating temperature of the slide bearing is measured. A value of the operating temperature of the slide bearing is regulated to maintain the operating value of the bearing modulus Aperf close to Acr in a range that is transitional between mixed-film lubrication and hydrodynamic lubrication.
The methods used at present to maintain a stable operating performance of a bearing involve increasing the factor of safety κ(Nλ/λratio) such that the bearing modulus (Hersey number) coming close to the critical values can be avoided as much as possible, since the antifriction materials most often used (tin babbitts, lead babbitts, lead bronzes, aluminum alloys, etc.) are quickly disrupted under conditions of mixed-film and boundary lubrication.
By way of example, the numerical parameters may be used, for example for a shaft of d=80 mm, l/d=1 and bearing modulus ξ=17*10−8. In the classical design of the bearing, the values of the maximum and minimum clearance are ξ=0.15-0.7, κ=3.1-8.4, f=0.027-0.05. In this case, the calculated coefficient of friction close to the critical bearing modulus λcr (point a in
The claimed method is based on the use of the properties of modern antifriction materials for varying the bearing parameters with no mechanical intervention, in particular, varying the friction coefficient, the related clearance, and the viscosity of the lubricant. The range of the parameter data is determined by the choice of the antifriction material with corresponding physical properties, and they are varied by changing the temperature in the friction zone of the bearing. As a result, control of the output characteristics of the friction unit may be achieved, particularly control of rotations and load, which expands the range of the performance characteristics of the friction unit; of friction, which reduces the friction losses, the heat dissipation, the oil consumption, and lowers the starting torque; the wear on the antifriction layer, which increases the service life and allows for breaking-in of the surface and the shape; and the clearances, which reduces self- oscillations and vibrations in different frequency ranges.
Table 1 shows the values for the minimum film thickness of lubricant film.
The physical properties of modern antifriction materials provide for good breaking-in of bearings for any types of lubrication. At the same time, the material roughness amounts to a few microns or less, allowing a significant decrease in the film thickness of lubricant film for a stable operation of the bearing, the bearing modulus λ, and the friction coefficient f (see Table 2).
Modern antifriction materials are able to operate at temperatures of minus 110 to plus 250° C., which allows the use of the viscosity of the used lubricants in a broad range of values, expanding the fluid lubrication regime in the direction of lower values of λ.
From the prior art, a technical solution is known aimed at lengthening the service life of a slide bearing (see U.S. Pat. No. 4,501,534, published 26 Feb. 1985), in which the speed of rotation is decreased in order to decrease the values of λ in air conditioning equipment, which is not always possible, except in the case of industrial equipment.
The dependency of physical characteristics (in particular, tensile and compressive limits, the modulus of elasticity, hardness, etc.) of antifriction materials on temperature allows varying of surface conditions for interaction of rubbing surfaces in slide bearings, which in turn allows decreasing of the breakaway torques and breaking-in not only of the roughness, but also the shape of the sliding surface of the bearings.
Control of the lubricant temperature also makes it possible to regulate the thermal expansion of the bearing parts and compensate for the clearances between the rubbing surfaces which are formed due to geometry deviations, design and fabrication errors, and frictional wear.
Technical solutions are known from the prior art, which are aimed in particular at compensating for clearances by introducing complex design changes in the bearing (see U.S. Pat. No. 8,303,185 published 9 Jul. 2010 and U.S. Pat. No. 7,559,697 published 14 Jul. 2009).
Technical solutions are known that are aimed at maintaining the temperature in bearings, for example, Chinese Patent Publication No. 110513398 published 29/11/2019, Japanese Patent Publication No. JPH06134651, published 17 May 1994, U.S. Pat. No. 4.948,269 A published 14 Aug. 1990. However, these technical solutions are aimed at maintaining the temperature in roller bearings.
A system for heat dissipation from a roller bearing is disclosed in U.S. Pat. No. 4,948,269, published 14 Aug. 1990, in which the need to remove or supply heat from/to the bearing is determined on the basis of data obtained from thermostats which are designed to maintain the temperature in a given working range.
However, this method is aimed at controlling the operating condition of roller bearings, which have a different range of operating temperatures and different physical operating conditions as compared to slide bearings. The known method cannot be used to control the performance characteristic of the slide bearing.
A technical problem to be solved by the disclosure is to expand the functionality of the slide bearing and increase operating reliability thereof.
A technical result achieved by solving a technical problem is reducing friction losses during the operation of the slide bearing and decreasing starting torque thereof while at the same time expanding operational characteristics of the bearing without altering its design, reducing the influence of errors in design and fabrication of the bearing on its operation, and simplifying the design of the slide bearing by eliminating the need to introduce design changes in the bearing in order to protect it against overheating during operation.
The technical problem is solved, and the technical result is achieved, by virtue of the fact that the method for controlling a performance characteristic of a slide bearing includes the steps of: (a) determining the temperature dependence of the dynamic viscosity of the bearing lubricant; (b) determining the mixed-film lubrication to hydrodynamic lubrication transition temperature of the bearing; (c) determining, on the basis of the temperature dependence of the dynamic viscosity of the lubricant, the temperature dependence of the bearing modulus A(T) and the value of the bearing modulus λcr of the mixed-film lubrication to hydrodynamic lubrication transition of the bearing; (d) measuring the operating temperature of the bearing; (e) regulating the value of the operating temperature of the bearing in order to keep the operating value of the bearing modulus λperf close to λcr in a range corresponding to the transition between mixed-film lubrication and hydrodynamic lubrication. Preferably, λperf is maintained in the range of 1.05*λcr≥λperf≥1.10*2λcr.
A technical problem is solved, and a technical result is achieved, likewise in the following embodiment of the method.
In the method for controlling a bearing modulus of the slide bearing, in step (b) it is possible to regulate the value of the operating temperature of the slide bearing by means of varying one or more parameters from the following group: temperature of the lubricant of the slide bearing; temperature of the rubbing parts of the bearing; external temperature influence on the slide bearing; temperature of the housing of the slide bearing; flow rate of the lubricant in the friction zone.
An embodiment of a slide bearing that can be used to implement the provided method and which is provided with an antifriction working surface and includes a temperature sensor able to measure the current operating temperature of the slide bearing.
In one embodiment of the slide bearing, the antifriction working surface can be configured based on antifriction polymer materials.
In another embodiment, the slide bearing can further include one or more sensors from the following group: a speed sensor; a pressure sensor; temperature sensors for friction surfaces of the bearing; a temperature sensor for the lubricant; a temperature sensor for the bearing housing; a torque sensor; position sensors; vibrational sensors; a power consumption sensor.
By detecting the temperature and the bearing modulus Wer of the transition of the slide bearing from mixed-film lubrication to hydrodynamic lubrication and then maintaining the bearing modulus λperf close to λcr in a range that is transitional between mixed-film lubrication and hydrodynamic lubrication by means of regulating the operating temperature of the slide bearing, it becomes possible to reduce the power losses from friction and reduce the influence of errors and defects on the rubbing surfaces of the slide bearing. In addition, by maintaining the bearing modulus λperf close to λcr there is no need to make design changes to the slide bearing aimed at constant cooling of the bearing during its operation, since there is no possibility of the bearing reaching temperature values surpassing its operating capabilities. In other words, the design of the bearing is simplified, which in turn enables both a simplification of the fabrication of the bearing and an easier operation thereof. Because, as was shown above, the majority of the characteristics of the slide bearing depends on its operating temperature, regulating the value of the operating temperature of the bearing will allow a significant decrease in the influence of errors in the design and fabrication of the bearing on its operation.
Varying the bearing temperature prior to its starting allows decreasing the coefficients of static friction between the rubbing parts, which decreases the starting torque.
Thus, the claimed technical solutions provide for a reliable operation of the slide bearing and expand its functionality.
The claimed method of controlling the bearing modulus of the slide bearing is explained by drawings.
The provided method of controlling the bearing modulus of the slide bearing is implemented as follows.
The determination of the temperature dependence of the dynamic viscosity of the lubricant of the slide bearing and the temperature of the transition from mixed-film lubrication to hydrodynamic lubrication affords the possibility of determining the temperature dependence of the bearing modulus λ(T) for the bearing with any lubricant known to one skilled in the art. Based on the transition temperature value, it is possible to determine the value of the bearing modulus λcr for the transition of the slide bearing from mixed-film lubrication to hydrodynamic lubrication. After measuring the current operating temperature of the slide bearing by means of a temperature sensor situated inside the bearing, it becomes possible to regulate the value of the operating temperature of the slide bearing to maintain the operating value of the bearing modulus Aperf close to λcr in a range that is transitional between mixed-film lubrication and hydrodynamic lubrication, preferably in the range of 1.05*λcr≤λperf≤1.10*λcr, based on the obtained temperature dependence λ(T). Such a regulating can be realized by varying one or more parameters of the slide bearing: temperature of the lubricant of the slide bearing; temperature of the rubbing parts of the bearing; external thermal influence on the slide bearing; temperature of the housing of the slide bearing; flow rate of the lubricant in the friction zone.
The provided method is a flexible tool for changing the characteristics of the bearing to accomplish a broad range of tasks. The following embodiments can be given as exemplary embodiments of the method.
Changing the operating temperature of the bearing by changing the temperature of a frictional pair directly in the friction zone by changing the temperature of the antifriction layer and/or that of rubbing parts of the bearing (shaft, shaft journals, pads, cushions, liners, separators, etc.).
Changing the operating temperature of the bearing by changing the lubricant temperature in the bearing by changing the temperature of the lubricant at the inlet of the bearing, by changing the feed rate (consumption) of the lubricant in the friction zone, by changing the conditions of heat dissipation in the lubricant cooling zones, by heating the lubricant in storage devices or feeding devices, and so forth.
Changing the operating temperature of the bearing by changing the temperature of the bearing housing by changing the conditions for heat dissipation to the surrounding environment, by changing the temperature of the surrounding environment, by heating the bearing housing, and so forth.
The slide bearing for the implementation of the method for controlling the bearing modulus of the slide bearing can be any slide bearing known to one skilled in the art, which is provided with an antifriction working surface and which includes a thermal sensor able to measure the current operating temperature of the slide bearing. The antifriction working surface can be configured based on antifriction polymer materials.
Design elements A (see
All of the mentioned design elements are provided as examples and can have any desired design implementation known to one skilled in the art, this design embodiment not being a subject of consideration of the present application.
The value of the characteristics of the bearing Y′i is registered using installed sensors B, in particular a speed sensor; a pressure sensor; temperature sensors for the friction surfaces of the bearing; temperature sensors for the lubricant; temperature sensors for the bearing housing; torque sensors; position sensors; vibration sensors; a power consumption sensor, and so forth.
The regulating signals are transmitted to the elements A by means of control units C, which may be integrated, for example, in the enterprise control system, or any other information system D providing for data collection B, analysis, predicting and feedback thereof.
The operator may select one or more characteristics of the bearing Y′i(Ti), which need to be controlled by varying the temperature or thermal parameters, for example:
The choice of any other characteristics of the slide bearing or combinations thereof not indicated in the present specification as characteristics controlled by means of temperature or thermal parameters does not limit the application of the disclosed method to the methods for controlling other selected characteristics.
Table 1 Presently used values of the minimum film thickness of lubricant film.
Table 2 includes the root-mean-square value of the height of material surface roughness, μm, for each sample.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020140610 | Dec 2020 | RU | national |
The present application is a U.S. national stage application of PCT International Application No. PCT/RU2021/050203, filed Jul. 6, 2021, and published as PCT Publication WO/2022/124936 on Jun. 16, 2022, which claims priority to Russian Application No. 2020140610, filed on Dec. 9, 2020. The disclosures of the foregoing applications are hereby incorporated by reference in their entirety into the present application.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/RU2021/050203 | 7/6/2021 | WO |
