1、 Comparison between roller screw and ball screw
The bearing capacity of rolling screw mainly depends on the radius of curvature, the number of contact points, the hardness and smoothness of the contact surface.
Under the condition of the same contact surface hardness, smoothness and precision, roller lead screw has more contact points than ball screw, and the radius of curvature of the envelope circle of roller contact surface is far greater than that of ball screw steel ball, which determines that roller lead screw has higher bearing capacity than ordinary ball screw.
Comparison diagram of the number and radius of curvature of roller lead screw and contact circle of roller lead screw
2、 Classification and application of roller screw pair
According to the different structure, roller screw pair can be divided into planetary roller screw pair and circular roller screw pair. There are essential differences in the operation mode of the two rollers: the roller of the planetary roller screw pair has no axial movement relative to the nut during the revolution and rotation, while the circular roller screw pair has the axial circular movement relative to the nut except for the revolution and rotation movement.
Structure_ Planetary roller screw pair is mainly used in heavy load field, while circular roller screw is inclined to precision equipment.
Planetary roller lead screw has high bearing capacity and high reliability, which is mainly used in:
●Injection molding ●Pressure machine tool ●steel industry ●Military equipment ●Nuclear industry
Due to the small screw lead (1 ~ 2mm), the circular roller lead screw has a high lead resolution, coupled with its high load capacity and high reliability, it is mainly used in:
●Precision instrument ●Precision grinder ●medical apparatus and instruments●Aerospace
3、 Contact analysis of planetary roller screw pair under given load
Taking 3020 planetary roller lead screw as an example, the contact stress under given axial load is analyzed. The mesh element of each contact element is hexahedron element, so as to improve the calculation accuracy of CAE contact analysis. The analysis process is shown in the following figure:
Through the above analysis, it can be determined that the maximum contact stress of each contact element surface is located on the surface of roller spiral raceway. According to the relevant literature, when the surface hardness of GCr15 material for ordinary lead screw reaches HRC63 after heat treatment, the allowable contact stress can reach 4000mpa. It can be inferred that the rated static load of 3020 roller lead screw can meet the requirements.
4、 Numbering rules and meanings
5、 By product series of planetary roller screw
Planetary roller screw pair (gzr) with nut flange in the center and without axial preload
6、 Circular roller screw by product series
Circular roller screw pair (GzV) with nut flange in the center and without axial preload