Formerly known as single-row radial ball bearing, DGBB bearing is the most widely used rolling bearing. The characteristics of the bearing are small friction resistance and high speed. It can be used on parts bearing radial loads, combined radial and axial loads, and on parts that bear axial loads, such as low power motors, gearboxes of automobiles and tractors, machine tool gearboxes, general machinery, tools. With the rapid development of hybrid electric vehicles and electric vehicles, the smaller and lighter electric motors are required in terms of environmental protection. A smaller motor will output a lower power, but to ensure the same or higher output as the current engines, higher speed motors are needed. In order to make DGBB bearings withstand RPM in excess of 30,000 r/min (which is 1.5 times the limit speed of the bearing currently used), China bearing manufacturer DALIAN GUANGYANG BEARING CO., LTD. Will introduce you how to analyse and optimize the bearings.
(1) The lubrication
Choose the way of oil lubrication. Due to the high speed rotation of the rolling element and the cage, a large amount of lubricating oil will move to the outer diameter direction of the bearing under the action of centrifugal force, and the lubrication between the inner ring and the rolling element, or between the rolling element and the cage, is not sufficient. Insufficient lubrication will cause the adhesion of the internal parts and lead to the bearing sticking. Adding lubricating oil will increase the resistance and torque to prevent adhesion.
(2) The friction
The friction between the ball and the surface of the groove. When a DGBB Bearing rotates, the sliding friction between the ball and the surface of the groove is proportional to the speed of the bearing. The effect of sliding friction at normal speed can be negligible. However, it is very important to control the friction between the ball and the surface of the groove under ultra-high speed conditions because a sharp increase in friction will lead to an heat increase of the bearing.
The friction between the ball and the cage. Stamping steel wave cages and plastic crown cages are commonly used for DGBB bearings. The stamping steel cage is riveted by two halves of stamping wave shaped semi-cages with ball hole structure; the plastic crown cage is made of nylon resin reinforced with glass fiber. Both kinds of cages have spherical pockets with locks; there is friction between the ball and the cage pocket. Under normal rotation speed, the force acting on the ball and the cage is very small, and the friction force at the cage pocket is as negligible as that between the ball and the bearing ring. However, the circumferential velocity of the ball can reach 40 m/s or even higher under the ultra-high speed of 30,000 r/min, and the point stress between the ball and the cage increases. The plastic cages are self-lubricated and light in weight, so they are more suitable for high speed operation than the stamping steel cages. If the lubrication is insufficient under the ultra-high speed operation of the bearing, the friction between the ball and the cage pocket will increase the wear on pocket surface, and then the cage may fall out of the bearing.
(3) Cage strength
The use of plastic crown cages. When the plastic crown cage rotates at high speed, the outer surface of the cage will be deformed under the action of centrifugal force, and the cage will contact the outer ring of the bearing at this time. When the cage is in contact with the outer ring of the bearing, the bearing temperature increases. In addition, the cage with serious deformation will fracture due to the excessive stress on the circumference surface of the pocket. It is necessary to develop an enhanced cage structure that can withstand the deformation and failure caused by the centrifugal force mentioned above. The cage strength can be enhanced by increasing the wall thickness of the cage without changing the bearing width.
(1) Install the cover to control the oil flow
The inner bearing can be fully lubricated and the problem of insufficient internal lubrication of the bearing under the action of centrifugal force in ultra-high speed operation can be solved by installing a cover for DGBB bearing to prevent the oil from overflowing onto the bearing end face.
(2) Reduce friction
The slip between ball and bearing ring can be reduced by optimizing the groove diameter and ball diameter of DGBB bearing. The wear of the pocket surface can be effectively avoided by improving the lubricity of the pocket surface and reducing the impact force between the ball and the cage. Install the cover to increase the flow of lubricating oil. To reduce the impact force and wear between the ball and the cage by adjusting the gap between the ball and the cage pocket as well as the gap between the outer diameter of the inner ring and the inner diameter of the cage.
(3) Improve the cage strength
Thicken the cage wall of the existing DGBB bearing and improve the stiffness of the cages, so as to reduce the deformation of the cages under ultra-high speed operation, and avoid the fracture caused by the excessive stress on the cages' pocket surface.
