The oil seal device can prevent the invasion of dust, moisture, metal powder and other harmful substances from outside. Prevent lubricant leakage from the bearing housing. Therefore, the oil seal device for any operating conditions must always play a sealing, dust-proof purpose. It is not allowed to cause abnormal friction and burning. At the same time, the bearing disassembly, assembly and maintenance can be carried out smoothly.

When using the oil seal device, it is necessary to select the appropriate oil seal device according to various purposes and lubrication methods.

1. Non contact oil seal device

As an oil seal device which does not contact with the shaft and has no friction part, it has the structure of oil groove, oil slinger ring and labyrinth oil seal, which uses centrifugal force and small clearance to play a sealing role.

(1) Oil tank

The structure of the oil groove is a structure that uses the small clearance between the shaft and the housing cover and several grooves arranged on the small clearance to play a sealing role. In addition to the low-speed situation, only relying on the oil groove to prevent lubricant leakage is not effective, so it is more than the combination of oil slinger and labyrinth oil seal. In addition, the oil tank is filled with a lubricant with a consistency of about 200, which has a certain dust-proof effect.

The smaller the clearance between the shaft and the housing, the better the sealing effect. The two can not be contacted during operation. The values in the following table can be used to determine the clearance between the shaft and the shell of the oil groove structure during installation:

Shaft diameter (mm) radial clearance (mm)

25 ~ 0.4 below 50

50~200 0.5~1.5

The width of the oil groove is about 3 ~ 5mm, and the depth is about 4 ~ 5mm. The number of oil groove channels should be more than 3 when the groove is only sealed.

(2) Oil slinger

The centrifugal force of the rotator installed on the shaft is used to prevent oil leakage and prevent dust. The main purpose of oil slinger is to prevent oil leakage, which is used in the environment with less dust. The oil slinger is placed outside the shell to prevent the invasion of external dust and moisture by centrifugal force of the oil slinger.

(3) Labyrinth oil seal

Labyrinth oil seal is a concave convex combination with small clearance between shaft and housing, which is especially suitable for preventing oil leakage of high-speed shaft.

When assembling labyrinth oil seal, the radial and axial labyrinth oil seal clearance is shown in the following table:

Shaft diameter (mm) labyrinth oil seal clearance (mm)

Radial direction axial direction

25 ~ 0.41 ~ 2 below 50

50~200 0.5~1.5 2~5

2. Contact oil seal device

The contact oil seal device is a structure that the contact tip edge of synthetic rubber, synthetic resin and felt is in friction contact with the shaft and plays a sealing role. The oil seal ring with synthetic rubber sealing lip is the most common.

(1) Oil seal ring

Many oil sealing rings are used in places where foreign matters such as dust and moisture are easily invaded from the outside, or where lubricant leakage is prevented in the housing. Many structures and sizes of oil seal rings have been standardized (refer to jisb2402). In order to maintain the proper pressure, assemble more springs. Therefore, it can grind with the eccentricity and deflection of the shaft to a certain extent. The material of sealing lip is made of synthetic rubber, such as butadiene rubber, propylene, silicon, fluorine, etc., and ethylene tetrafluoride resin. The upper limit of allowable temperature is increased in the order of the above materials.

If there is no oil film between the sealing lip and the shaft, it is easy to cause heat and wear. Therefore, in the installation, the sealing ring must be coated with some oil. Moreover, in operation, it is ideal that the lubricant in the housing seeps out slightly from the sliding surface. The allowable circumferential velocity of oil seal ring varies with seal structure, finish machining degree of sliding surface, sealing object, temperature condition and eccentricity of shaft. The applicable temperature range is limited by the material of sealing lip. The allowable circumferential velocity and service temperature under good conditions are shown in the table below:

Allowable circumferential velocity of oil seal material (M / s) applicable temperature range (℃)

Synthetic rubber under 16 - 25 ~ + 100

Acrylic rubber below 25 - 15 ~ + 130

Silicon system below 32 - 70 ~ + 200

Fluorine below 32 - 30 ~ + 200

Trifluoroethylene resin below 15 - 50 ~ + 220

Note: for short time operation, it can be 20 ℃ higher than the upper limit of service temperature.

Under the condition of high-speed and high-precision machining, the internal shaft with high-speed of 0.5 mm is also required. In order to improve the wear resistance, the hardness of the sliding part of the shaft needs heat treatment or hard chromium plating, so that the hardness can reach hrc40, if it can reach HRC55 or above, it is more ideal.

The general standard of surface finish of sliding parts required by the circumferential speed of shaft is as follows:

Circumferential velocity (M / s) maximum surface finish R

3.2s below 5

5~10 1.6S

More than 10 0.8s

(2) Felt seal ring

Felt seal ring has been used for transmission shaft from a long time ago, but it is difficult to avoid oil leakage and penetration. Therefore, it is only used for dust-proof purpose of grease lubrication, and it is not suitable for the working condition of high circumferential speed of shaft.