Oil bath bearings achieve lubrication through oil circulation and oil film formation, and their working principle involves key links such as storage, circulation, oil film formation, and temperature control of lubricating oil. The following is a detailed explanation of the working principle of oil bath bearings:
1、 Lubricating oil storage and supply
Oil tank design:
Oil bath bearings are equipped with a dedicated oil tank for storing lubricating oil. The oil pool capacity shall be determined according to the bearing size, rotating speed and working environment to ensure that the lubricating oil is sufficient and will not produce too much foam due to mixing.
Oil level control:
The height of the oil pool liquid level is usually controlled slightly below the centerline of the lowest rolling element of the bearing (generally recommended to be near the center of the lowest rolling element of the bearing, or adjusted to 0.5-1 times the diameter of the rolling element below the centerline according to equipment requirements). This design can ensure that sufficient lubricating oil is carried by the rolling elements during rotation, while avoiding excessive oil volume that may cause increased mixing loss or high temperature rise.
2、 Lubricating oil circulation mechanism
Oil carrying process:
When the bearing is running, the rolling elements (such as balls or rollers) will immerse in the oil pool during rotation, carrying lubricating oil up and adhering to the surface. As the rolling elements roll, lubricating oil is evenly applied to the contact surfaces of the bearing inner ring, outer ring, and cage.
Gravity reflux:
The lubricating oil attached to the rolling elements gradually drips under the action of gravity and flows back to the oil pool, forming a continuous cycle. Part of the lubricating oil may be thrown to other parts inside the bearing due to centrifugal action, further expanding the lubrication range.
Splash lubrication supplement:
Under high-speed or heavy load conditions, the rotation of gears or bearing components may produce splashing effects, which scatter lubricating oil to a wider area and enhance lubrication effectiveness.
3、 Formation of oil film and lubrication effect
Boundary lubrication stage:
During bearing start-up or low-speed operation, a boundary lubrication film may form between the rolling elements and the raceway. At this point, additives in the lubricating oil (such as anti-wear agents and extreme pressure agents) form a chemical adsorption film on the contact surface, reducing direct metal contact.
Fluid dynamic lubrication stage:
As the speed increases, the lubricating oil carried by the rolling elements forms a sufficiently thick oil film between the contact surfaces, completely separating the two contact surfaces. At this point, the frictional force mainly comes from the viscous resistance inside the lubricating oil, significantly reducing wear.
Elastic fluid dynamic lubrication (EHL):
Under high load conditions, elastic deformation may occur in the contact area, forming a thicker oil film. Polymer additives in lubricating oil can enhance oil film strength and prevent oil film rupture.
4、 Temperature control and heat dissipation
Thermal conduction:
Lubricating oil absorbs the heat generated by bearing operation during the circulation process, and conducts the heat to the external environment through the oil pool wall or heat dissipation device (such as heat sink, cooling pipe) to prevent bearing overheating.
Convection heat dissipation:
The flow of lubricating oil in the oil pool promotes convective heat transfer and accelerates heat dissipation. In high temperature or continuous operation scenarios, forced cooling devices (such as oil coolers) can be added to improve heat dissipation efficiency.
5、 Impurity filtration and oil maintenance
Filtering system:
To prevent impurities from entering the interior of the bearing, the oil tank is usually equipped with filtering devices (such as filter screens, magnetic adsorbers) to regularly remove metal particles, dust, and other pollutants.
Oil testing:
Regularly check the viscosity, acid value, moisture content, and pollution level of lubricating oil. If the oil deteriorates (such as a decrease in viscosity or an increase in acid value), it should be replaced in a timely manner to avoid worsening bearing wear.