What is the difference between cylindrical roller bearings and needle bearings?
1. From the shape point of view, there are two criteria for the difference between the needle roller and the roller: the first is that the ratio of 2.5 is the boundary point. The second standard is based on a ratio of 4.
2. From the point of view of force, the needle roller does not bear axial force at all (the end face of the needle roller is not ground, if it is in contact with the shoulder, the friction is very large), and the roller, if the raceway has a shoulder If you can withstand a certain axial force, of course not too big, the principle is not to exceed 1/10 of the radial force.
3. From the application point of view, the needle roller is mainly used in places where space is limited, so it is widely used in automobiles, motorcycles and textile machines. Moreover, the inner ring of the needle roller is optional. To put it bluntly, if the hardness and roughness of the shaft meet the requirements, the inner ring may not be matched (the space is inherently limited), but if the machining degree of the shaft is relatively low, or relatively soft, An inner ring is required as a raceway.
Rollers are often used to support the floating end of the shaft to absorb the amount of expansion of the shaft. The four rows of rollers on the machine are used more, mainly because the roller bearing capacity is very large.
4. The structure and application of the needle roller are very flexible and vary a lot. It is common to have no inner ring needles, but it is also common without the outer ring, even without a cage. Of course, the outer ring can also have different changes. It can be a physical circle (machined) or a punched ring. Today's trend on engine crankshafts is to replace the bearing pads with loose needles (which can reduce friction -> fuel economy), and the application of a wide range of zero-gear needles on the steering column of the car, the structure is even more special.
5. The thrust bearing of the roller is rare (at least I have not seen it), but the thrust bearing of the needle roller is widely used, such as a large number of applications in the automatic transmission, such as air compressors.
6. Looking at the world, the needle roller is still the strongest INA, followed by Torrington (now TIMKEN). It is worth mentioning that Torrington invented the thrust piece and carried forward the needle thrust bearing. (Simple prompt: the needle roller is straight, but the thrust bearing is a circular motion, so the needle thrust bearing must have a large sliding friction. In the limited space, how to design the needle thrust bearing to reduce the friction is very technical. content)
In short, the needle roller and the roller are definitely not just the difference in size.