Calculation of radial displacements of nut and rollers axes and the position of a contact between the nut and the roller thread in an inverted planetary roller screw mechanism

Inverted planetary roller screw mechanisms (PRSM) are used in a variety of drives in machine-building, aircraft, oil and gas industries, etc. Currently, such mechanisms are widely used in manufacturing the so-called electric cylinders. The difference of lead angles of the rollers and the nut causes radial misalignment of rollers axes, which results in mechanism preload. The preload affects the mechanism accuracy and efficiency and, in some cases, prevents its assembly. It is obvious that the value of the radial displacement of the axes of rollers relative to the axis of a nut should be taken into account to obtain a required mechanism preload and efficiency. This paper presents analytical relationships for calculating the position of initial contact points of accurate nut and roller threads, as well as an increase in axial distance between rollers and nut axes caused by the difference of their lead angles. Accounting for changes in axial distance makes it possible to design efficient mechanisms and estimate the magnitude of the preload required to run the mechanism and ensure its best efficiency.

References

[1] SKF compact inverted roller screw. Brochure.

[2] SKF Catalogue roller screen 2005–2008. Publication 4351 EN – 2008-01. France, 88 p.

[3] Blinov D.S., Riakhovskii O.A., Sokolov P.A. Sposob izmereniia profilei rez’b rolikov planetarnykh roliko-vintovykh peredach i obrabotka rezul’tatov [A method for measuring the thread profile of the planetary roller screw roller gear and processing of results]. Vestnik mashinostroeniia [Russian Engineering Research]. 1998, no. 7, pp. 26–29.

[4] Blinov D.S., Riakhovskii O.A., Sokolov P.A. Chislennyi metod opredeleniia tochki pervonachal’nogo kontakta vitkov dvukh vintov s parallel’nymi osiami i razlichnymi uglami pod"ema rez’by [A numerical method for determining the point of initial contact turns two screws with parallel axes and various angles of ascent thread]. Vestnik MGTU im. N.E. Baumana. Ser. Mashinostroenie [Herald of the Bauman Moscow State Technical University. Ser. Mechanical Engineering]. 1996, no. 3, pp. 93–96.

[5] Biderman V.L. Mekhanika tonkostennykh konstruktsii. Statika [Mechanics of thin-walled structures. Statics]. Moscow, Mashinostroenie publ., 1977. 488 p.

[6] Drong V.I., Dubinin V.V., Il’in M.M., Kolesnikov K.S. Kurs teoreticheskoi mekhaniki [Course of Theoretical Mechanics]. Moscow, Bauman Press, 2000. 736 p.

[7] D’iakonov V.P. Mathematica 5.1/5.2/6 v matematicheskikh i nauchno-tekhnicheskikh raschetakh [Mathemat ica 5.1/5.2/6 in mathematical , scientific and technical calculat ions]. Moscow, SOLON-Press publ., 2008. 744 p.