The method of determining the lubricity of oils

 

(57) Abstract:

The invention relates to techniques for assessing the quality of liquid lubricants, in particular to the determination of their lubricating ability. The method of determining the lubricity of oils is that exploit a pair of friction in the presence of lubricants, flow through it of an electric current, remove static electricity on the surfaces of friction pairs by changing the polarity of the electric current, measure DC current with a stationary pair of friction at steady state friction in the presence of lubricant in the contact and measure the amount of current during the period from the beginning of the test to stabilize its value at the steady state friction regime in a time-dependent friction, load, sliding velocity, mechanical properties of materials, bearings and oil temperature, build graphical dependencies and evaluate the lubricity of the oil parameters: adaptability, speed, adaptability oil to these conditions of friction and the coefficient of compatibility of oil, while the flexibility of the oil is determined by the period of time from the beginning of the current reduction to its stabilization, speed, adaptability, on the corner of N. the mule

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where IC- set the amount of current flowing through a pair of friction in the stillness; IWITH- the value of DC current when its stabilization in the process of friction. Improved reliability assessment of lubricity oils. 7 Il.

The invention relates to techniques for assessing the quality of liquid lubricants, and in particular to the determination of their lubricating ability.

There is a method of determining the lubricity of oils, namely, that exploit a pair of friction in the presence of lubricants, flow through it of an electric current, a lubricity appreciate with regard to one of the parameters of the electric current (AC USSR 796732, CL G 01 N 3/56, 1979).

A disadvantage of the known technical solution is the low reliability of the results of determination of lubricity of oils, due to the influence on the electric current factors such as material properties of the friction pair, the mode of friction (load, sliding speed, oil temperature) that determine the speed of mechanochemical processes in frictional contact and education on it protective structures (films).

The closest in technical essence and the achievement of laterbut pair of friction in the presence of a lubricant, pass through it of an electric current, remove static electricity on the surfaces of a friction pair by changing the polarity of the electric current, measure DC current with a stationary pair of friction and steady state friction in the presence of lubricant in the contact, and the option to use their relationship (as the USSR 1054732, CL G 01 N 3/56, 1983).

The known method is objectively not provide full information on the lubricating ability of the oil, as determined for one of the selected pairs of materials and friction regimes, and changing them can lead either to decrease or to increase the ratio of currents. Therefore, the indicator lubricating ability of the test oil cannot be transferred to other materials of the pair of friction and the friction regimes, because it depends on them. Information about the influence of the friction pair materials and modes of friction on the lubricity of oils increases the reliability of their estimates.

The objective of the invention is to increase the reliability assessment of lubricity oils by taking into account the influence of the modes of friction and material properties of the friction pair.

The problem is solved in that in the method of determining the lubricity of oils, including operation the supply on the surfaces of friction pairs by changing the polarity of the electric current, DC current measurement with fixed pair of friction and steady state friction in the presence of lubricant in the contact according to the invention to measure the amount of current during the period from the beginning of the test to stabilize its value at the steady state friction regime in a time-dependent friction, load, sliding velocity, mechanical properties of materials of the friction pair, oil temperature, build their graphical dependencies and evaluate the lubricity of the oil according to the parameters of adaptability, speed, adaptability oil to these conditions of friction and the coefficient of compatibility of oil, while the flexibility of the oil is determined by the period of time from the beginning of the current reduction to its stabilization, speed adaptability - angle graphic dependencies to the ordinate axis, and the coefficient compatibility TOWITHoil is determined by the formula

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where IC- set the amount of current flowing through a pair of friction during immobility;

IWITH- the value of DC current when its stabilization in the process of friction.

Comparative analysis of the prototype and the proposed method showed that the latter has the following distinctive features.

The construction of the graphical dependencies of current change from time allows you to visualize the nature of the manifestations of mechanochemical processes in frictional contact, depending on the properties of the oil regimes of friction and material properties of the friction pair. According to the graphical dependency is determined by the period of time from the beginning of the current reduction to its stabilization, which is used as a parameter characterizing the variability of oil depending on the friction parameters and material properties of the friction pair, which is aimed at improving the reliability of the assessment of lubricity of the oil.

The angle of graphical dependencies to the axis of ordinates over a period of time from the beginning of the current reduction to its stabilization is used as a parameter characterizing the rate adaptability of the oil at different regimes of friction and material properties of the friction pair. This option also increases the reliability of evaluation of the lubricity of the oil.

The current stabilization in the graphical dependencies used as a parameter to characterize the intensity of the flow of mechanochemical processes under steady state friction and determines a dynamic equilibrium between the rates of formation and destruction of protective layers on friction surfaces, it also increases the reliability of evaluation of the lubricity of the oil.

Determination of the coefficient of compatibility of oil as the ratio of the difference between the values of the currents specified at a fixed pair of friction and stabilization to the magnitude of the current stabilization allows you to compare the percent of the lubricating properties of the various oils compatibility depending on the materials of the pair of friction and friction regimes that are aimed at improving the reliability assessment of lubricity oils.

In Fig. 1 presents a diagram of the device for implementing the method of Fig. 2 shows the graphical dependence of the magnitude of the current flowing through a pair of friction of the load, and Fig.3 - dependence of the current value of slip speed; Fig. 4 - dependence of the current on the oil temperature, and Fig. 5 - dependence of current on changes in temperature tempering hardened steel 45; Fig.6 - dependence of the residual current from the optical density employed in internal combustion engine oils; Fig.7 shows the write current flowing through a pair of friction (on the recorder).

The device comprises a pair of friction 1, source 2 stable DC current, resistor 3 to adjust velikin chart recorder (not shown), node 6 to change the polarity of the electric current.

The method of determining the lubricity of oils is as follows.

In a stationary state is brought into contact friction and resistor 3 (Fig.1) determine the amount of current of 100 µa (50... 200 µa). Operate a pair of friction in the presence of lubricants under different regimes of friction (load, sliding speed, oil temperature), remove static electricity on the surfaces of friction by changing the polarity of the electric current, measure the amount of current within 90 minutes (or recorded by a recorder). On the recorded graphical dependencies determine the period of time from the beginning of the current reduction to its stabilization.

This period characterizes the flexibility of the oil at different regimes of friction and material properties of friction and determines the intensity of mechanochemical processes contributing to the formation of protective layers.

Determine the angle of graphical dependencies to the axis of the ordinates for the period from the beginning of the current reduction to its stabilization. The angle of the graphical dependencies determine the speed of adaptability oil dependent, depending on the mode of friction, which determine the coefficient of compatibility TOWITHoil by the formula

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where IC- set the amount of current (100 μa);

IC- the value of DC current when its stabilization in the process of friction.

Determine the lubricity of the oil according to the parameters of adaptability, and the coefficient of compatibility, which establish the most effective scope of the test oils depending on the load, sliding velocity, temperature and material properties of the friction pair.

Example 1. Consider changing lubrication oil M-10G2from the parameters of friction and a constant pair of steel materials SH-15. Using source 2 and resistor 3 (Fig.1) set the value of the constant current ICwithin 50...200 µa, which is measured by the indicator 4 (or recorded by a recorder). Operate a pair of friction in the presence of grease and measure DC current depending on the load P (Fig.2). As can be seen, the period of time from the beginning of the current reduction to its stabilization least for a load of 30 N, and the maximum load 40 N, this is due to the formation of protective films on the surfaces of friction. The angle of slope of this dependence is minimal for narrowest friction materials.

The coefficient of the compatibility of the tested oils, judging by the current stabilization of IWITHequal to 100%.

Thus, the lubricity of the oil M-10G2to the maximum load of 30 N.

Change lubricating ability of the oil M-10G2from sliding velocity is shown in Fig.3. On the graphic dependences shows that the period adaptability minimum for a sliding velocity of 0.34 and 0.68 m/s, and the velocity adaptability greatest velocity of 0.34 m/s, the coefficient of compatibility maximum (100%) was observed for sliding speeds 0,17; of 0.34 and 0.68 m/s

For a sliding velocity of 0.08; 0.11 and 1.02 m/s period adaptability is much larger and the coefficient of compatibility ranges from 85 to 70%. Therefore, the lubricity of the oil M-10G2to largest at the sliding velocity of 0.34 and 0.68 m/s, and the most effective use of oil is in the range from 0.17 to 0.68 m/s

The influence of oil temperature on its lubricity shown in Fig. 4. As can be seen, the period of adaptability and speed adaptability respectively the minimum and maximum observed for the temperature TO 375 (100oC). Furthermore, with the reduction neobyasnimy fact, with decreasing temperature, the rate of formation of protective films decreases ceteris paribus (load, sliding speed). Factor compatibility maximum 100% for temperatures 353...373 K (80... 100oC) and decreases with a decrease in oil temperature. Thus, the lubricity of the oil M-10G2to the maximum at a temperature of 373 K (100oC), and the most effective use of oil is in the range from 80 to 100oC.

Considering the impact of modes of friction (load, sliding speed, oil temperature) on the lubricity of the investigated oils M-10G2K (Fig. 2-4), we can conclude that the most efficient use of oil for the pair of friction materials from SH-15 steel meets the following limits modes: load - 10 to 40 N; sliding speed from 0.17 to 0.68 m/s, the oil temperature is from 80 to 100oWith the period of adaptability is minimal, and the speed of adaptability, and the ratio of maximum compatibility.

Example 2. Consider the effect of friction pair materials for a period of adaptability, speed, adaptability, and the coefficient of compliance of oil M-10G2K. To this end one Sakaki (Fig. 5). Mechanical properties of steel 45 changed by changing the tempering temperature. As can be seen from the graphical dependency period adaptability least, and speed maximum adaptability for steel 45, vacation 423 K (150oC). With increasing the tempering temperature (reduction of mechanical properties) period adaptability is increased, and the speed of adaptability decreases. Factor compatibility decreases with increasing the tempering temperature of the steel 45. For annealed steel 45 (1123 K) is 0%.

Thus, the maximum lubricity oil M-10G2it is observed for the pair of friction steel 45, vacation 423 To - steel SH-15. As bearings can be used and steel 45, vacation 573 K (300oC).

Example 3. Consider the effect of oil M-10G2to its lubricity, depending on time use in internal combustion engines (Fig.6). For this purpose, samples of oil were taken from the engine at regular intervals and subjected to photometry to determine the optical density D, which depends on the operational concentration of impurities. When testing such samples of oils modes friction made permanent, and the Mat is functioning oil M-10G2it strongly depends on its properties change during use in engines.

The minimum period of adaptability and maximum speed adaptability are observed for oils with optical density D=0,89...1.0, and the coefficient of compatibility for them equal to 90%.

Thus, the period of adaptability, speed, adaptability, and the coefficient of compatibility for selected pairs of materials and modes of friction depends on the properties of the lubricant.

Graphic dependence recorded by the recorder shown in Fig.7, to determine the period of adaptability, speed, adaptability, and the coefficient of compliance.

The advantages of the proposed method are that it allows you to obtain additional information to improve the reliability assessment of lubricity oils by such characteristics as flexibility, speed, adaptability, and the coefficient of compatibility depending on the materials of the pair of friction, friction properties of oil on the values of these parameters to determine the optimal mode of friction.

Information about the proposed options can objectively osushestvim materials of the pair of friction and friction regimes.

The positive effect is due to the increase in the reliability assessment of lubricity of oils depending on the material properties of the friction pair, regimes of friction and oil properties.

The method of determining the lubricity of oils, namely, that exploit a pair of friction in the presence of lubricants, flow through it of an electric current, remove static electricity on the surfaces of a friction pair by changing the polarity of the electric current, measure DC current with a stationary pair of friction and steady state friction in the presence of lubricant in contact, characterized in that the measured value of the current for the period from the beginning of the test to stabilize its value at the steady state friction regime in a time-dependent friction, load, sliding velocity, mechanical properties of materials, bearings and oil temperature, build graphical dependencies and evaluate the lubricity of the oil parameters: adaptability, speed, adaptability oil to these conditions of friction and the coefficient of compatibility of oil, while the flexibility of the oil is determined by the period of time from the beginning of the current reduction to its stabilization, speed proposable is determined by the formula

< / BR>
where IC- set the amount of current flowing through a pair of friction during immobility;

IWITH- the value of DC current when its stabilization in the process of friction.

 

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