The difference between sliding bearing and rolling bearing first appears in the structure. Sliding bearing supports the rotating shaft by a smooth surface, so the contact part is a surface; The rolling bearing supports the rotating shaft by the rotation of the rolling element, and the contact part is a point. The more rolling elements, the more contact points. Secondly, the motion mode of rolling bearing is rolling; The motion mode of sliding bearing is sliding, so the friction situation is completely different.
The sliding bearing works stably, reliably and noiseless. Under the condition of liquid lubrication, the sliding surface of the sliding bearing is separated by the lubricating oil without direct contact. It can also greatly reduce the friction loss and surface wear. The oil film also has a certain vibration absorption capacity. However, the starting friction resistance is large. The part of the shaft supported by the bearing is called the journal, and the parts matching the journal are called the bearing bush. In order to improve the friction properties of the bearing surface, the antifriction material layer cast on its inner surface is called bearing lining.
The materials of bearing bush and bearing liner are collectively referred to as sliding bearing materials. Common sliding bearing materials include bearing alloy (also known as Babbitt alloy or white alloy), wear-resistant cast iron, copper based and aluminum based alloys, powder metallurgy materials, plastics, rubber, hardwood and carbon graphite, polytetrafluoroethylene (PTFE), modified Polyoxymethylene (POM), etc. Sliding bearing applications are generally under low-speed and heavy-duty working conditions, or operating parts where maintenance and lubricating oil filling are difficult.
Rolling bearing is a kind of precision mechanical element that changes the sliding friction between the running shaft and the shaft seat into rolling friction, so as to reduce the friction loss. Rolling bearing is generally composed of outer ring, inner ring, rolling element and cage. The function of the inner ring is to match with the shaft and rotate with the shaft. The function of the outer ring is to match with the bearing seat and play a supporting role. The rolling element evenly distributes the rolling element between the inner ring and the outer ring with the help of the cage. Its shape, size and quantity directly affect the service performance and service life of the rolling bearing. The cage can evenly distribute the rolling element and prevent the rolling element from falling off, The rolling element rotates for lubrication.
Compared with sliding bearing, rolling bearing has large radial size, poor damping capacity, low service life and large sound at high speed. The radial bearing (mainly bearing radial force) in rolling bearing is usually composed of inner ring, outer ring, rolling element and rolling element cage. The inner ring is tightly sleeved on the journal and rotates with the shaft, and the outer ring is installed in the bearing seat hole. A raceway is arranged on the outer circumference of the inner ring and the inner circumference of the outer ring.
When the inner and outer rings rotate relative to each other, the rolling elements roll on the raceway of the inner and outer rings. They are separated by a cage to avoid mutual friction. The thrust bearing is divided into two parts: tight ring and movable ring. The tightening ring is tight with the shaft sleeve, and the movable ring is supported on the bearing seat. The ring and rolling element are usually made of rolling bearing steel with high strength and good wear resistance. The surface hardness after quenching shall reach HRC60 ~ 65. The cage is mostly made of mild steel, or copper alloy cloth, bakelite or plastic.