1 Experimental equipment and methods 1 DCS-150 gear test bench principle 11 Experimental equipment for coal machine gear transmission mostly belongs to low speed and heavy load. The test uses DSC-150 closed power flow gear test bench, which is convenient and accurate to load. Automatic planetary loading mode.
The working principle is as shown in Fig. 1. The test box and the test box are respectively cooled in two ways: natural heat dissipation and forced circulation water cooling. The test gear pair is manufactured by the hard tooth grinding process, because only the hard tooth gear transmission can meet the requirements of high power, high bearing capacity, small volume and light weight, so the gear transmission in the modern coal machine equipment almost adopts hard teeth. Lubricating oils are selected from the six oils in the test samples. This is because the surveys of the Huainan, Huaibei and Yanzhou mining areas have been known to be the commonly used varieties in coal mines. In order to ensure the accuracy of the test, the kinematic viscosity of the six oils was measured before the test.
1 Lubricating oil measured viscosity and recommended viscosity value Grade measured viscosity value temperature / °C moving viscosity / (m2
S-1) Manual recommended viscosity value temperature / °C kinematic viscosity / (m2
S-1) 120# gear oil 100201129918190 gear oil 10014124991318030 gear oil 1003018410029100～31100SHC630 gear oil 100251611002413268 mechanical oil 1002111810016160～2910018 hyperbolic oil50521585065100～71100
12 Test method In order to eliminate the mutual interference between multiple factors, find out the main influencing factors and related factors, based on the comprehensive consideration of the characteristics of coal mine machinery working conditions, the test uses the single factor comparison test method, the test is carried out according to the following two groups:
(1) For the actual working conditions of the constant speed variable load of cutting parts, belt conveyors and scraper conveyors of roadheaders and shearers, the test uses constant working speed variable load method to analyze different lubricating oil pairs. The effect of gear meshing efficiency and lubrication conditions. The aim is to provide a digital reference for the rational selection of gear-driven lubricants in such equipment.
(2) For the actual working conditions of the constant load variable speed of the walking and loading parts of the roadheader and the shearer, lifting and dispatching equipment, the test uses the constant working torque variable speed method to analyze the different lubricating oil to gear meshing. The effect of efficiency and lubrication conditions is intended to provide a theoretical basis for the rational selection of gear-driven lubricants in such equipment.
2 Test results and analysis 21 The effect of lubricating oil on efficiency at constant working speed 21 Whether it is gear reducer used in roadheader or shearer, or used on scraper conveyor and belt conveyor for raw coal and material transportation The gear reducer has a working speed of about n=1000r/min. For the working conditions of this type of equipment, the test selects the working speed n=1000r/min. The test adopts the step-by-step loading mode. The load (transferred torque) varies from T=200 to 700Nm, and the load per stage increases by 100Nm. Increase to the big step by step. The data collection time is after the test chamber reaches the heat balance (the sign of the heat balance is that the oil temperature in the test chamber no longer climbs), and the continuous operation is 20 min at this temperature. The measured data results are as shown in 2, and it can be seen that:
(1) When the load is not large (torque T ≤ 500 Nm, power P ≤ 52 kW), the efficiency curve is steep, the efficiency is improved, the oil temperature is high, and the corresponding efficiency is high. It shows that even if the viscosity of the lubricating oil is low, the elastic oil film can be formed on the meshing tooth surface. At this time, the main power loss is the power consumption of the oil, the viscosity of the high temperature lubricating oil is lowered, and the power loss is small. Therefore, in order to ensure the effective lubrication of the tooth surface, in order to reduce the power consumption of the oil, the low viscosity oil should be used.
(2) When the load is large (torque T>500Nm, power consumption P>52kW), regardless of the cooling method used, the efficiency curve is gentle and the efficiency does not change much. It shows that the viscosity of the lubricating oil has a great influence on the meshing tooth surface, which is easy to form the dynamic oil film, and the oil viscosity is high, which is good for forming the dynamic oil film on the meshing tooth surface. The meshing power loss is small (sliding frictional power loss is small), and the main power loss at this time It is the meshing power loss. Therefore, the lubricating oil with higher viscosity should be used as much as possible to improve the friction and wear of the meshing tooth surface.
(3) Under the condition of small load (torque T≤500Nm, use power P≤52kW), for the same kind of lubricating oil, natural heat dissipation cooling is better than circulating water cooling, and its efficiency is higher than circulating water cooling. This shows that at low load, the meshing tooth surface is easy to form a power oil film, and the power loss of the gear transmission is mainly the power consumption of the oil. The reason is that the cooling effect by natural heat dissipation is poor, causing the temperature of the lubricating oil to rise and the temperature to rise rapidly, causing the viscosity of the lubricating oil to decrease, and the power loss of the gear stirring oil is small.
(4) Under the condition of large load (torque T>500Nm, use power P>52kW), for the same kind of lubricating oil, circulating water cooling is better than natural heat dissipation, and the efficiency of natural heat dissipation is not significant or even decreased. At this time, the power loss is mainly the gear meshing power loss, and the ratio of the oil consumption to the total power consumption is getting smaller and smaller. The main reason is that the influence of temperature on the viscosity of the lubricating oil is good. The cooling effect of the circulating water is good, the temperature of the lubricating oil is low, and the viscosity of the lubricating oil is small, which is advantageous for forming the dynamic oil film on the meshing surface of the gear.
(5) The test results of the selected Mobil SHC630 lubricating oil are different from other experimental results, and an abnormal phenomenon occurs. The efficiency curves of the two cooling modes are very similar, and the efficiency curves intersect when no high load occurs, and under the same test conditions Compared with other types, it has the highest efficiency value and the lowest working temperature rise. The main reason is that this oil is a synthetic oil with an extreme pressure additive. The dynamic oil film can be formed well regardless of the load, and the effect on the thickness of the oil film is not obvious. It can be seen that regardless of the load size, a synthetic lubricant containing an extreme pressure additive with moderate viscosity is the best choice.
(6) At high load, if high-viscosity lubricating oil cannot be selected at the site, a cooling method with good cooling effect can also be used to improve the influence of temperature on the viscosity of the lubricating oil, maintain the stability of the viscosity, and ensure the formation of the dynamic oil film of the meshing tooth surface. The anti-wear and anti-friction effect is obtained, and the transmission efficiency and service life of the gear are improved.
22 Effect of Lubricating Oil on Efficiency under Constant Torque There is another working condition in coal mine machinery: fixed load, variable speed, such as the traveling mechanism of the roadheader, winch for lifting and dispatching equipment, etc. For this kind of working condition, the test adopts the method of constant load, that is, the holding torque is constant (torque T=600Nm), the working speed is set to 500~1000r/min during test, the speed is 100r/min, and the speed conversion method is adopted. From small to large, the other conditions are the same as those in Section 211, and the measured data is as shown. The results showed that:
(1) At low speeds, the oil temperature is low and the efficiency is low; the oil temperature is high and the efficiency is high. It shows that the viscosity of the lubricating oil has a great influence on the power loss. When the temperature is low, the viscosity of the lubricating oil is high, resulting in a large loss of the power of the stirring oil. For such working conditions, it is recommended to use a lubricant with a low viscosity.
(2) At high speeds, the oil temperature is low and the efficiency is high; the oil temperature is high and the efficiency is low. Explain the influence of the rotational speed and the viscosity of the lubricating oil on the formation of the dynamic oil film. The temperature is high, although the viscosity of the lubricating oil decreases, but as the rotating speed increases, the meshing power loss (sliding frictional power loss) and the oil loss of the oil increase. However, the increase in meshing power loss is more pronounced, resulting in a decrease in work efficiency. At this time, it is suitable to use a lubricating oil having a high viscosity.
(3) Under the same oil temperature, the high oil temperature state, that is, the natural heat dissipation cooling, the high rotation speed and low efficiency, the efficiency gradually decreases with the increase of the rotation speed. This means that the normal lubricating oil film cannot be formed when the lubricating oil temperature is high, so that the gear meshing tooth surface is in direct contact, which increases the friction loss power between the gear meshing surfaces, resulting in a gradual decrease in efficiency. At this time, a high-viscosity lubricating oil should be used to ensure that the tooth surface forms a good lubricating oil film.
(4) Under the same oil temperature, the low oil temperature state, that is, the circulating water cooling, the high speed and high efficiency, with the increase of the speed, the efficiency is gradually improved. This also shows that a good lubricating oil film can be formed when the lubricating oil temperature is low, the friction and wear between the gear meshing tooth surfaces are improved, and the friction loss power between the gear meshing surfaces is reduced. Under the premise of ensuring normal lubrication, a low viscosity lubricant can be used to reduce the power loss of the oil.
(5) It can be clearly seen from the comparison that under the same test conditions, Mobil SHC630 gear oil has the highest efficiency and the lowest working oil temperature, which proves that its lubricating performance is the best. Regardless of the rotational speed, it is most desirable to use a synthetic lubricant containing an extreme pressure additive with a suitable viscosity.
(6) The test result of No. 30 gear oil showed an abnormal phenomenon. The low oil temperature state of circulating water cooling, when n<700r/min, the efficiency decreases with the increase of the rotational speed; when n>700r/min, the efficiency increases with the increase of the rotational speed; when n=700r/min, It is the inflection point of the efficiency curve, and the efficiency is the lowest. The main reason is that the viscosity of No. 30 gear oil is the highest. When the oil temperature is low and low (n<700r/min), the viscosity is high and the power loss of the oil is large. This indicates that the main power loss is mainly the power loss of the oil. Large; low oil temperature, high speed (n>700r/min), high viscosity, can improve the friction and wear of the tooth surface, the meshing power loss is small, indicating that the main power loss at this time is mainly the meshing power loss. With the high oil temperature state of natural heat dissipation, the test results are just the opposite. However, for both cases, when the rotation speed is higher than 900r/min, the efficiency is not obvious with the increase of the rotation speed. This shows that when the rotational speed is higher than 900r/min, the meshing power loss and the power loss of the oil are balanced, and the rotational speed has little effect on the efficiency. It can be seen that when selecting high-viscosity lubricating oil, the actual working conditions should be comprehensively investigated. When the rotating speed is low, it should not be used. When the rotating speed is high, it is most suitable for selection, and it is also beneficial to ensure the flank lubrication of the tooth surface.
3 Conclusions (1) Under the condition of constant speed (n=1000r/min): When the working load is not large (torque T≤500Nm, power P≤52kW), the power loss is mainly the power consumption of the oil. Under the premise of ensuring effective lubrication of the tooth surface, the low-viscosity lubricating oil and the natural heat-dissipating cooling method should be used as much as possible. No matter whether it is designed or used, it is not necessary to consider forced cooling; when the working load is high (torque T>500Nm, the power P is used) >52kW), the power loss is mainly the gear meshing power loss. In order to improve the friction and wear of the meshing tooth surface, the high viscosity lubricating oil and circulating water cooling method should be used as much as possible.
(2) Under the working condition that the working load is constant (torque T=600Nm, power consumption P=63kW), the power loss is mainly the oil consumption of the oil at low speed, and the viscosity of the lubricating oil has a great influence on the power loss. Lubricating oil with low viscosity and natural cooling method; at high speed, as the speed increases, the meshing power loss (sliding friction loss) and the oil loss increase, but the meshing power loss increases more obviously. In order to reduce the friction and wear between the gear meshing surfaces, high viscosity oil and circulating water cooling should be used.
(3) No matter what kind of working conditions, Mobil SHC630 synthetic gear oil with extreme pressure has good lubricity, which is beneficial to the formation of dynamic lubricating oil film. Besides anti-friction and anti-wear effect, it also has excellent anti-foaming property. Separation from water should be a priority.
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