The sealing principle and application of skeleton oil seal

The skeleton oil seal is a typical representative of the oil seal. Generally speaking, the oil seal refers to the skeleton oil seal. The function of the oil seal is generally to isolate the parts that need to be lubricated in the transmission parts from the output parts, so as to prevent the leakage of lubricating oil. The skeleton is like the steel bars in the concrete member, which acts as a reinforcement and enables the oil seal to maintain its shape and tension. Skeleton oil seals are widely used in aviation, automobiles, motorcycles, railways, vehicles, ships, home appliances, construction machinery and other industries. Suitable for rotary motion and reciprocating motion seals. Installed in various heavy-type engines, gearboxes, axles, ships, cylinders and other parts. Mainly prevent the penetration of the sealed medium (gas, liquid) and the entry of external foreign bodies into the body. According to the structure, it can be divided into single lip skeleton oil seal and double lip skeleton oil seal. The auxiliary lip of the double-lip skeleton oil seal plays a dust-proof role to prevent external dust and impurities from entering the machine. According to the skeleton type, it can be divided into inner skeleton oil seal, exposed skeleton oil seal and assembled oil seal. According to working conditions, it can be divided into rotary skeleton oil seal and reciprocating skeleton oil seal. For gasoline engine crankshafts, diesel engine crankshafts, gearboxes, differentials, shock absorbers, engines, axles and other parts. The skeleton oil seal structure consists of three parts: the oil seal body, the reinforced skeleton and the self-tightening coil spring. The sealing body is divided into bottom, waist frame oil seal structure diagram, cutting edge and sealing lip according to different parts. Generally, the inner diameter of the skeleton oil seal in the free state is smaller than the shaft diameter, that is, it has a certain“interference”. Therefore, after the oil seal is installed on the oil seal seat and the shaft, the pressure of the oil seal edge and the contraction force of the self-tightening coil spring will generate a certain radial tightening force on the shaft. After a period of operation, the pressure will rapidly decrease or even disappear. , Therefore, adding a spring can compensate the self-tightening force of the oil seal at any time. Sealing principle: Since there is an oil film controlled by the oil seal edge between the oil seal and the shaft, the oil film has fluid lubrication characteristics. Under the action of the skeleton oil seal, the rigidity of the oil film just makes the oil film and the air contact end form a crescent surface, preventing the leakage of the working medium, thereby realizing the sealing of the rotating shaft. The sealing ability of the oil seal depends on the thickness of the oil film on the sealing surface. If the thickness is too large, the oil seal will leak; if the thickness is too small, dry friction may occur, causing oil seal and shaft wear; if there is no oil film between the sealing lip and the shaft, it is easy to cause heat and wear. . Therefore, when installing, it is necessary to apply some oil on the sealing ring, and at the same time ensure that the skeleton oil seal is perpendicular to the axis line. If it is not perpendicular, the sealing lip of the oil seal will drain the lubricating oil from the shaft, which will also lead to excessive sealing of the lip. wear. During operation, the lubricant in the casing seeps out a little, so that it is ideal to form an oil film on the sealing surface. The function of the skeleton oil seal is generally to isolate the parts that need to be lubricated in the transmission parts from the output parts, so that the lubricating oil will not leak. It is usually used for rotating shafts and is a kind of rotating shaft lip seal. The skeleton is like the steel bars in the concrete member, which acts as a reinforcement and enables the oil seal to maintain its shape and tension. According to the skeleton type, it can be divided into inner skeleton oil seal, outer skeleton oil seal, and inner and outer skeleton oil seal. The skeleton oil seal is made of high-quality nitrile rubber seals and steel plate, with stable quality and long service life. Widely used in automobiles, motorcycle crankshafts, camshafts, differentials, shock absorbers, engines, axles, front and rear wheels and other parts. 1. Prevent sediment, dust, moisture, etc. from intruding into the bearing from the outside; 2. Limit the leakage of lubricating oil in the bearing. The requirements for the oil seal are that the dimensions (inner diameter, outer diameter and thickness) should meet the regulations; appropriate elasticity is required to properly clamp the shaft and play a sealing role; it must be heat-resistant, wear-resistant, strong, and resistant to media ( oil or water, etc.), long service life. Reasonable use of oil seals should pay attention to the following points: (1) Due to the design and structural reasons of shaft speed, high-speed oil seals should be used for high-speed shafts, low-speed oil seals should be used for low-speed shafts, and low-speed oil seals cannot be used for high-speed shafts. , and vice versa. (2) The oil seal with general pressure has poor pressure bearing capacity, and the oil seal will be deformed when the pressure is too large. Under the condition of excessive pressure, a pressure-resistant bearing ring or a reinforced pressure-resistant oil seal should be used. (3) When the ambient temperature is high, polyacrylate or silicon, fluorine, and silicon fluorine rubber should be selected. And should try to lower the oil temperature in the tank. When the operating temperature is too low, cold-resistant rubber seals should be used. (4) The degree of eccentricity on the installation If the eccentricity of the oil seal and the shaft is too large, the sealing performance will be deteriorated, especially when the shaft speed is high. If the eccentricity is too large, the“W”Oil seal with shaped section. (5) Note that there should be a certain amount of lubricating oil on the lip of the oil seal. (6) Special attention should be paid to prevent dust from immersing in the oil seal. (7) The surface finish of the shaft directly affects the service life of the oil seal, that is, the higher the shaft finish, the longer the service life of the oil seal. Company website: https://www.orksealing.com/
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