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Smooth method commonly used in high speed bearings
Source: China Bearing Network Time: 2018-01-29
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The working temperature of high-speed bearings is mostly around 200 °C; and tends to be higher; if not cooled, the temperature will continue to rise and the strength and hardness of the bearing will be too high; once the bearing loses its ability to adhere to the exact shape; Aggravation of high-speed conflicts causes the temperature to rise agilely; further incurs a decrease in data strength and hardness, causing the bearing to quickly fail.
Because the high-speed bearing is very sensitive to wear; but it is simple to wear debris; if it is not removed from the bearing in time; it will also constitute a vicious circle;
Therefore, the mission of high-speed bearing smoothness is necessary to effectively send the smoothing agent to the moving appearance in the bearing; and take away the heat from the bearing; together with the abrasive debris in the bearing.
The smooth methods commonly used in high speed bearings and useful smoothing agents are:
1. Spray illuminating method is to spray smooth oil from the nozzle hole of the bearing near the bearing; spray the bearing at a speed of 10 20 m/s; generally it is sprayed into the gap formed by the bracket and the inner ring or the outer ring; And the way to cool the bearings.
For small ball bearings with an inner diameter of 30-35mm; the limit of dmn can reach 3 million for jet gliding; 2.5 million for larger bearings.
Double-hole or multi-hole nozzles can increase the oil supply; it can also improve the power of smooth oil; multi-nozzles or nozzles on both ends; can improve the smoothness and cooling effect; but when the dmn value is nearly 2 million Because of the influence of centrifugal inertia and wind resistance; the oil fed into the bearing is only 70% or less of the nozzle flow.
2. The smoothing method under the ring is a centrifugal inertia; the oil is directly sprayed onto the outer surface of the raceway through a plurality of radial small holes formed in the inner ring, and a part of the oil moves axially under the inner ring to reach the cooling. The intention of the circle. The oil entering the raceway will flow out to the left and right of the two channels; the sputum will be washed away from the abrasive debris falling from the parts such as the support frame.
The smoothing method uses much less oil than the injection; the power loss caused by the power mixing of the oil is less; the heating condition of the bearing is also greatly improved; and even the inner ring temperature can be lower than the outer ring. Bearing failure rate.
This smooth method can be used to cool the outer ring. When inside; the outer ring is so smooth; the bearing's dmn value can be further improved.
Nowadays, this ring-smooth method is widely used in various ultra-high-speed work places. The maximum dmn value that can be reached; 3 million large ball bearings with inner diameter of 120-200mm, and 2.4 million tapered roller bearings with inner diameter of 120mm; The short cylindrical roller bearing for the inner ring is 3 million. The two-layer smoothing method essentially consists of forming the hydrostatic oil film sliding bearing of the inner ring hole and the journal of the rolling bearing; the rotation speed of the rolling bearing is greatly reduced; then the intention of reducing the centrifugal force effect is reached; such a two-layer smooth bearing Can significantly reduce the speed of the inner ring of the rolling bearing; therefore, the spindle is allowed to have a higher speed; equivalent to the dmn value of the bearing can be further improved.
4. The biggest advantage of the oil and gas smoothing method is that the bearing has no need to change the bearing layout; the dmn value can be completed at a speed of 800,000 to 1.5 million only through the conflict of the descending bearing; The strengths are more obvious.
(1) Principle of oil and gas smoothing and its characteristics The principle of oil and gas smoothing is to use a quantitative piston type distributor to discharge a very small amount of oil (for example, 0.011 m1); intermittently discharging at an optimal cycle; the discharged oil is before it reaches the bearing. Forming a continuous flow with air feeding into the bearing.
The characteristics of oil and gas smoothness are as follows:
1) It can supply a very small amount of quantitative oil to the bearing stably; it can control the minimum amount of oil as smooth grease. Because the bearing type is different; the demand for smooth oil is different; Pass to each set of bearings; this can adjust the oil supply of each bearing.
The kinetic collision of this smooth method is about one-tenth of the gliding and sliding; its motion conflict is lost and the temperature rise is also smaller than the grease.
2) Because the oil and gas is smoother than the slick and slick oil; and the smooth oil flows into the bearing with suitable oil droplets; therefore, the atmosphere is less polluted. For example, the smooth spindle of the oil and gas is placed in the propylene box for about 2 hours; the measuring box The degree of air pollution is only 0. 03mg/m3.
3) It is difficult for foreign dust cutting fluid to enter the spindle; this is because of the large amount of air accompanying the supply of trace oil (30 L/min per bearing); the reason for the internal pressure of the spindle is improved.
(2) Oil and gas smooth oil quantity and viscosity Oil and gas smoothness should be supplied with the necessary minimum amount of oil; therefore, the selection of oil quantity is very important.
The angular contact ball bearing with more sliding is more oil than the cylindrical roller bearing with less sliding. The general specification of the oil supply quantity has a formula.
However, the lower the viscosity of the oil; or the higher the rotational speed; the amount of oil required increases accordingly. In fact, the amount of oil should be determined according to the bearing load and the rotational speed.
In terms of the effect of smooth oil viscosity on bearing temperature rise; oil and gas smoothness is much smaller than cyclic oil supply. However, under the same oil supply conditions; when the viscosity is high; the temperature rise is slightly improved. The general oil and gas smoothness is 40 At °C; use oil with a viscosity of 10 3Cmrn2 / s.
Gas smoothness is a new and successful method with a variety of characteristics; it is used in bearings with more sliding, such as angular touch bearings; its dmn value can reach about 1.5 million.
5. Smoothing agent for high-speed bearings The smoothing agent for high-speed bearings should be considered as a smoothing agent for high-temperature bearings; that is, a component oil that also has excellent functions at high temperatures; or a smooth grease based on such a constituent oil. MIL L 7808 oil and MIL L 23699 oil; used more in jet engine bearings.
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