Ball splines were standardized by JIS in 2004 and now they are examined in ISO / TC39 as power transmitting components. In this paper the ball load distribution and basic dynamic load rating for ball spline type AII are discussed theoretically by considering the re-circulation of balls in each row including a spline shaft bending deformation with radial load and the crownings of nut raceway both end portions. The ball load distributions in case of even arrangement, condition I for the effective number of balls,
Zt =
Zt I = 9 and uneven arrangement, condition II for the effective number of balls, also
Zt =
Zt II = 8 are discussed with ball re-circulation. The results are as follows. (1) Under the application of pure torque, the ball load distributions for each condition I and II are even except the crowning portions and the shaft deformation does not occur, and maximum ball load in condition II is shown
Pmax II ≤ 1.03
Pmax I in accordance with ball re-circulation. (2) Under the application of pure radial load, the ball load fluctuation is
Pmax II ≤ 1.19
Pmax I without shaft deformation and further
Pmax II ≤ 1.15
Pmax I with shaft deformation. (3) Under the application of combined radial load and torque, the ball load fluctuation is
Pmax II ≤ 1.07
Pmax I in case of without shaft deformation and further
Pmax II ≤ 1.07
Pmax I with shaft deformation. (4) The basic dynamic load rating
CF* for ball spline can be classified into pure torque
CMx, pure radial load
CFy, combined radial load and torque
CFy+Mx etc. In case of pure torque, the
CMx value by this report is agreed with ISO's load rating for condition I theoretically. (5) In case of combined radial load and torque, it is made clear that the load rating for
CFy is remarkably decreased in accordance with the increase in load eccentricity and
CFy+Mx value approaches to the basic dynamic load rating for pure torque
CMx.
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