Load distribution of rollers considering errors in planetary roller screw mechanism

Abstract:

To improve the load distribution of rollers thread, based on the relationship of deformation compatibility on two contact sides of the roller, a model of load distribution of the roller thread considering errors is established when the screw shaft withstands tension and the nut withstands compression. The load ratios among the roller thread teeth are compared with the results of direct stiffness method to verify the correctness of the presented method. Then the factors, such as load, contact angle, helix angle, number teeth of the roller thread and material Young's modulus ratio, which affect the load distribution of the roller thread are systematically studied. The results show that the smaller the load, the larger the fluctuation of load distribution on teeth of the roller thread. The negative errors are able to decrease load ratios of the fore 3 teeth of the roller thread. The load distribution is more even by decreasing the contact angle or helix angle. Increasing the number teeth leads to the decrease of the load ratios and the influence of error on load ratios. Besides, it is helpful to improve load distribution of roller thread by decreasing the Young's modulus of the screw or the nut.