The structural form of planetary rack depends largely on the use function,the method of manufacturing planetary rack and the assembly condition of planetary gear reducer.The reasonable planetary frame structure should be small in outline size and light in weight,which can ensure the uniform distribution of load between planetary wheels and the uniform distribution of load along the meshing tooth width,and have good processing and assembly technology,so that the planetary gear transmission has high bearing capacity and small vibration and noise.

　　At present,there are several types of planetary frame structures commonly used in planetary gear transmission

　　(1)overall frame structure

　　In a transmission with a number of planetary wheels greater than 2,the planetary frame is usually a spatial frame structure composed of two annular side plates 1 and 2(or double walls)connected by uniformly distributed brace(also called connecting plate).The number of struts is equal to the number of planetary wheels,and the lateral size of struts is determined by the size of the planetary wheel.Planet wheel bearing is installed inside a planetary wheel,frame structure is more suitable at this time in this planet,otherwise due to the transmission ratio is small,the planetary wheel diameter is small,in order to guarantee the service life of the planet wheel bearing has certain,will force bearing arrangement in the side panel,cause the planet carrier side panel thickness increases,and transmission of the axial profile size is also increased.The overall frame structure has good stiffness and little influence on thermal expansion,so it is widely used.

　　(2)welding structure and casting structure

　　If the planetary frame is manufactured with integral forgings,the amount of cutting is not only large,but also a large number of metal into chips,material consumption is more.Therefore,planetary rack blank can be obtained by welding or casting.At this time,the blank size is very close to the actual size of the planetary shelf.When making the planetary frame of welding or casting structure,the procedure of eliminating internal stress should be stipulated in the process,otherwise,in the process of mechanical processing,and in the process of transmission operation,the planetary frame may produce a larger deformation.Planetary racks of welded construction are often used in single piece production.

　　(3)cantilever structure with detachable side plate

　　For die-forged planetary frame,a cantilever structure with detachable side plates can be used.For the convenience of assembly,the planetary rack can adopt the cantilever structure without axle diameter,and the combined structure with detachable journal or detachable side plate.This kind of planetary frame is composed of forging parts.The application of composite structure is mainly related to the assembly technology of planetary gear drive.

　　(4)single-sided planetary wheel shaft;Cantilever integral structure

　　In order to obtain the planetary gear transmission with smaller outline size,the number of planetary gears must be increased greatly.This would force the removal of the planetary strut and the use of an integral planetary strut with only one side plate and a cantilevered planetary wheel shaft.The stiffness of this kind of structure can be strengthened by ring tendons,but the stiffness is smaller than that of the whole frame structure with two side plates.

　　(5)composite structure

　　In overloaded planetary gear transmission,the characteristics of the structure from the shore in the middle part of the input or output torque,installing planetary shaft components of the structure is symmetrical,as if the planet more shore and side plate deformation,also can produce a planetary wheel under the wheel axis deflection axis relative to the center,to ensure uniform distribution load along the meshing tooth width.