How to choose the bearing lubrication method? Bearing lubrication methods are roughly divided into two types: grease lubrication and oil lubrication. In order to give full play to the function of the bearing, it is important to adopt the corresponding lubrication method according to the use conditions and purpose of the bearing.

Bearing grease

Grease is a lubricant composed of base oil, thickener and additives. When choosing, you should choose a grease that is very suitable for the bearing conditions. Due to the different trademarks of the grease, there will be great differences in performance, so you must pay attention when choosing. Commonly used greases for bearings include calcium-based grease, sodium-based grease, calcium-sodium-based grease, lithium-based grease, aluminum-based grease, and molybdenum disulfide grease. The amount of grease filled in the bearing is suitable to fill 1/2-1/3 of the inner space of the bearing. It should be reduced to 1/3 at high speed. Excessive grease tends to increase the temperature of the bearing in operation.

Grease selection

When selecting grease according to the working temperature, the main indicators should be dropping point, oxidation stability and low temperature performance. Dropping point can generally be used to evaluate high temperature performance, bearing The actual working temperature should be 10-20°C lower than the dropping point. The operating temperature of synthetic grease should be 20-30°C lower than the dropping point. When selecting grease according to bearing load, select grease with small penetration for heavy load. When working under high pressure, in addition to the small penetration, it also has high oil film strength and extreme pressure performance. When selecting a grease based on environmental conditions, calcium-based greases are not easily soluble in water and are suitable for dry and low-moisture environments.

Bearing lubricating oil

Under the conditions of high speed and high temperature, oil lubrication can be used when grease lubrication is not suitable. Through the circulation of lubricating oil, a lot of heat can be taken away. Viscosity is an important characteristic of lubricating oil. The size of the viscosity directly affects the fluidity of the lubricating oil and the thickness of the oil film formed between the friction surfaces. The viscosity of the lubricating oil at the working temperature of the bearing is generally 12-15cst. The higher the rotational speed, the lower the viscosity should be, and the heavier the load should be, the higher the viscosity should be. Commonly used lubricating oils are mechanical oil, high-speed mechanical oil, turbine oil, compressor oil, compressor oil, cylinder oil, etc.

Lubricating oil method

Oil bath lubrication: Oil bath lubrication is the most common lubrication method, suitable for the lubrication of low and medium speed bearings. A part of the bearing is immersed in the oil groove, and the lubricating oil is carried by the rotating bearing parts. , and then flow back to the oil sump, the oil level should be slightly lower than the center of the lowest rolling element.

Drip lubrication: Drip lubrication is suitable for bearing components that require a quantitative supply of lubricating oil. Generally, the amount of oil dripping every 3-8 seconds is appropriate. Too much oil will cause the bearing temperature to increase.

Circulating oil lubrication: The oil pump is used to transport the filtered oil to the bearing parts, and the lubricating oil after passing through the bearing is filtered and cooled before use. Because the circulating oil can take away a certain amount of heat and cool the bearing, this method is suitable for bearing parts with high rotation speed.

Spray lubrication: use dry compressed air to mix with s lubricating oil through a sprayer to form an oil mist. In the jet bearing, the airflow can effectively cool the bearing and prevent the intrusion of impurities. This method is suitable for the lubrication of high-speed, high-temperature bearing parts.

Jet lubrication: use an oil pump to inject high-pressure oil into the bearing through a nozzle, and the oil injected into the bearing flows into the oil tank through the other end of the bearing. When the bearing rotates at a high speed, the rolling elements and the cage also make the surrounding air flow at a relatively high rotation speed. It is difficult to send the lubricating oil to the bearing by the general lubrication method. At this time, the lubricating oil must be sprayed with high pressure injection method. To the bearing, the position of the nozzle should be placed between the inner ring and the center of the cage.

The choice of lubricant and lubrication method for rolling bearings is related to the type, size and operating conditions of the bearing. Generally, rolling bearings are lubricated with grease or oil. Solid lubrication can be used. Among grease lubrication and oil lubrication, grease lubrication is the most used, and about 80% of rolling bearings are greased.

1. Characteristics of grease lubrication (1) Advantages of grease lubrication

A: The lubrication device is simple. s If sealed bearings or non-sealed bearings that do not require regreasing are used, no additional lubrication is required (by contrast, oil lubrication systems require oil pumps, oil pipes, oil tanks, etc.).

B: The grease is not easy to leak, and the sealing structure of the bearing is relatively simple.

C: The maintenance and maintenance of the bearing are convenient.

D: The grease has a sealing function to prevent external dust, moisture and other impurities from entering the bearing.

E: It is easy to improve the cleanliness of mechanical devices.

(2) Disadvantages of grease lubrication:

A: The bearing has large friction and poor heat dissipation, and the allowable speed is relatively low.

B: The dn value of grease lubricated bearings generally cannot exceed 3×105mm·r/m·n.

C: When the temperature is very high, the base oil of the lubricating grease will accelerate the evaporation and oxidative deterioration, and the colloidal structure of the lubricating grease will also change and accelerate the oil separation.

Every time the bearing temperature increases by 10℃-15℃, the life of the grease will decrease by 1/2. Except for special high-temperature grease, general grease cannot be used at high temperature.

2. Characteristics of oil lubrication---Advantages

A, suitable for high-speed rotation

B, good high temperature stability, suitable for use in high temperature.

C. It can take away the frictional heat inside the bearing, and the heat dissipation is good. When the ambient temperature of the bearing is high, oil lubrication can play a cooling role.

D. It is easy to remove the wear particles and dust inside the bearing.

E. It can share a lubricant with the parts around the bearing such as gears, and implement common lubrication.