Oil Film Bearing
A bearing is a machine element designed to support a moving part, decrease the amount of friction between moving parts, and minimize vibration and any noise. The two main groups among bearings are rolling element bearings and hydrodynamic (or fluid film) bearings. Oil film bearings, also known as hydrodynamic bearings, are composed of three parts: a shaft, a bearing surface, and a film of lubricant—generally oil—that is pushed to the pressure between the two metal surfaces. This oil film provides the necessary cushion to prevent metal-to-metal contact, which would cause excessive noise and wear.
The primary forces involved in oil film bearings are hydrodynamic forces. Hydrodynamic forces are created by high-speed relative motion between mating surfaces, and they are the basic forces that lifts and separates the moving parts of a bearing. As the relative motion occurs, a layer of lubricant forms a wedge between the neighboring surfaces. This wedge prevents them from coming into direct contact and facilitates separation of the two surfaces at points of pressure. The height of the wedge is directly related to the load on the bearing, and is maintained as long as there is relative motion between the surfaces.
The oil film generated between the shaft and bearing surfaces in an oil bearing works to support the weight of the shaft during operation. As the shaft rotates, tangential forces are created, pressing the oil into the small gap between the shaft and bearing surfaces. The oil can then move around to prevent any direct contact from occurring and reduce wear on the surfaces. The oil also helps dissipate heat away from surfaces in contact, reducing the friction and minimizing damage to the bearing surface.
In addition to tangential forces, hydrodynamic pressure is necessary to maintain the oil film between a shaft and its bearing surface. As the shaft accelerates, hydrodynamic pressure is generated, pushing the oil further into the gap between the two surfaces. This pressure is generated by a combination of the rotation of the shaft and the acceleration of the shaft. The pressure increases as the relative speed goes up, creating a stable oil film between the surfaces. As the pressure and the film are increased, so is the load-carrying capacity of the bearing.
Oil film bearings are a versatile, effective option for reducing friction in a wide variety of applications and environments. They are suited to high-speed applications and high load-carrying situations where bearing service life is important. Oil film bearings are highly configurable and have a wide range of sizes, shapes, and materials to choose from, making them adaptable to any application. Whether in motors, pumps, turbines, or any other machine, oil film bearings are an excellent choice for reducing friction, dampening vibration, and extending service life.
