ROLLER TAPER GRINDING METHOD FOR PLANETARY ROLLER SCREW MECHANISM

20240131650 · 2024-04-25

Inventors

Cpc classification

International classification

Abstract

Disclosed is a roller taper grinding method for a planetary roller screw mechanism. The method includes steps as follows: step 1: determining basic parameters and a bearing capacity of a planetary roller screw mechanism to be machined; step 2: establishing deformation and force balance equations of the planetary roller screw mechanism according to the basic parameters and the bearing capacity of the planetary roller screw mechanism determined in step 1; step 3: iteratively computing an optimal grinding taper angle of roller grinding according to the deformation and force balance equations established in step 2; step 4: determining process parameters of roller grinding; and step 5: grinding a roller taper of the planetary roller screw mechanism by a machine tool according to the process parameters determined in step 4.

Claims

1. A roller taper grinding method for a planetary roller screw mechanism, comprising steps as follows step 1: determining basic parameters and a bearing capacity of a planetary roller screw mechanism to be machined: step 2: establishing deformation and force balance equations of the planetary roller screw mechanism according to the basic parameters and the bearing capacity of the planetary roller screw mechanism determined in step 1; step 3: iteratively computing an optimal grinding taper angle of roller grinding according to the deformation and force balance equations established in step 2; step 4: determining process parameters of roller grinding; and step 5: grinding a roller taper of the planetary roller screw mechanism by a machine tool according to the process parameters determined in step 4.

2. The roller taper grinding method for a planetary roller screw mechanism according to claim 1, wherein the basic parameters of the planetary roller screw mechanism in step 1 comprise major diameters, nominal diameters, minor diameters, thread angles, helix angles, thread pitches, thread starts of a screw, a roller and a nut, an external diameter of the nut, an arc radius of the roller, number of rollers, and number of threads per roller

3. The roller taper grinding method for a planetary roller screw mechanism according to claim 2, wherein the deformation and force balance equations of the planetary roller screw mechanism established in step 2 are: ${\begin{matrix} P_{S} + ? ? = P_{R} + ? ? ? P_{R} \tan ? \\ P_{N} + ? ? = P_{R} + ? ? ? P_{R} \tan ? \\ .Math. ? F ? = \frac{F}{z_{R}} \\ .Math. ? F ? = \frac{F}{?} \end{matrix}$ $? indicates text missing or illegible when filed$ wherein P.sub.S, P.sub.R and P.sub.N are the thread pitches of the screw, the roller and the nut respectively; i is a thread number of the roller, i=1, 2, 3, . . . N.sub.t, and N.sub.t is number of threads per roller; ?l.sub.Si and ?l.sub.Ni are axial deformation at an i.sub.th segment of the screw and the nut respectively; ?l.sub.SRi and ?l.sub.NRi are axial deformation of the roller on a screw side and a nut side respectively; ? is a grinding taper angle of the roller; F.sub.SRi and F.sub.NRi are axial forces borne by an i.sub.th thread on the screw side and the nut side respectively; F is a load value of the planetary roller screw mechanism; Z.sub.R is a number of rollers; and ? indicates a tension and compression state of the screw or the nut, + indicates tension, and ? indicates compression.

4. The roller taper grinding method for a planetary roller screw mechanism according to claim 3, wherein in step 3 of iteratively computing an optimal grinding taper angle according to the deformation and force balance equations established in step 2, the grinding taper angle ? of the roller in the deformation and force balance equations in step 2 is gradually increased from 0, and corresponding axial forces F.sub.SRi and F.sub.NRi borne by the thread on the screw side and the nut side are capable of being obtained in the case of any ?; and when loads are most uniformly distributed on the screw side or the nut side, the grinding taper angle ? stops being increased, and the grinding taper angle at a stop moment is recorded as the optimal grinding taper angle ?.sub.opt of roller grinding.

5. The roller taper grinding method for a planetary roller screw mechanism according to claim 4, wherein the process parameters of roller grinding in step 4 comprise a mounting angle ? of a grinding wheel, a rotational speed ?.sub.G of the grinding wheel, a rotational speed ?.sub.R of a machined roller, and an axial movement speed v.sub.G of the grinding wheel; and an axial movement direction of the grinding wheel is a direction determined based on the optimal grinding taper angle ?.sub.opt in step 3.

6. The roller taper grinding method for a planetary roller screw mechanism according to claim 5, wherein in step 4, the mounting angle ? of the grinding wheel is the same as a helix angle of the machined roller, the rotational speed ?.sub.G of the grinding wheel is determined by a machining capability of a machine tool and characteristics of the grinding wheel, the rotational speed ?.sub.R of the machined roller and the axial movement speed v.sub.G of the grinding wheel satisfy a relation of v.sub.G=?.sub.RP.sub.R, and P.sub.R is a thread pitch of the machined roller.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present disclosure will be further described below in combination with accompanying drawings.

[0023] FIG. 1 is a schematic structural diagram of a planetary roller screw mechanism according to the background art of the present disclosure;

[0024] FIG. 2 is a schematic diagram of a front view of roller taper grinding according to detailed description of the embodiments of the present disclosure;

[0025] FIG. 3 is a schematic diagram of a top view of roller taper grinding according to detailed description of the embodiments of the present disclosure;

[0026] FIG. 4 is a roller not subjected to taper grinding according to detailed description of the embodiments of the present disclosure;

[0027] FIG. 5 is a roller subjected to taper grinding according to detailed description of the embodiments of the present disclosure; and

[0028] FIG. 6 is a schematic comparison diagram of types of part of threads of a roller subjected to taper grinding and not subjected to taper grinding according to detailed description of the embodiments of the present disclosure.

[0029] Description of reference numerals: 1. screw, 2. roller, 3. nut, 4. retainer ring, 5. inner gear ring, 6. retainer, 7. grinding wheel, 8. thread after roller taper grinding, and 9. thread before taper grinding.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The present disclosure will be described in further detail below in combination with accompanying drawings. The present disclosure will be described in further detail below in combination with accompanying drawings. The embodiments are implemented on the premise of the technical solution of the present disclosure, and detailed implementation modes are provided, but the scope of protection of the present disclosure is not limited to the following embodiments.

[0031] As shown in FIGS. 2-6, a roller taper grinding method for a planetary roller screw mechanism includes steps as follows:

[0032] step 1: determine basic parameters and a bearing capacity of a planetary roller screw mechanism to be machined, where specifically, the basic parameters of the planetary roller screw mechanism include major diameters, nominal diameters, minor diameters, thread angles, helix angles, thread pitches, thread starts of a screw, a roller and a nut, an external diameter of the nut, an arc radius of the roller, number of rollers, and number of threads per roller

[0033] In the embodiment, the bearing capacity is 30 kN, and specific values of the basic parameters are as shown in Table I:

TABLE-US-00001 TABLE 1 Basic parameters of planetary roller screw mechanism in embodiment Parameter Screw Roller Nut Major diameter (mm) 19.875 6.875 32.95 Nominal diameter (mm) 19.5 6.5 32.5 Minor diameter (mm) 19.05 6.05 32.125 Thread angle (?) 90 90 90 Helix angle (?) 4.66 2.8 2.8 Thread pitch (mm) 1 1 1 Thread starts 5 1 5 External diameter of nut (mm) \ \ 42 Arc radius of roller (mm) \ 9.19 \ Number of rollers (mm) \ 10 \ Number of threads per roller \ 30 \

[0034] Step 2: establish deformation and force balance equations of the planetary roller screw mechanism according to the basic parameters and the bearing capacity of the planetary roller screw mechanism determined in step 1:

[00002] ${\begin{matrix} P_{S} + ? ? = P_{R} + ? ? ? P_{R} \tan ? \\ P_{N} + ? ? = P_{R} + ? ? ? P_{R} \tan ? \\ .Math. ? F ? = \frac{F}{z_{R}} \\ .Math. ? F ? = \frac{F}{?} \end{matrix}$ $? indicates text missing or illegible when filed$

[0035] where P.sub.S, P.sub.R and P.sub.N are the thread pitches of the screw, the roller and the nut respectively; i is a thread number of the roller, i=1, 2, 3, . . . , N.sub.t, and N.sub.t is number of threads per roller; ?l.sub.Si and ?l.sub.Ni are axial deformation at an i.sub.th segment of the screw and the nut respectively, ?l.sub.SRi and ?l.sub.NRi are axial deformation of the roller on a screw side and a nut side respectively; Y is a grinding taper angle of the roller; F.sub.SRi and F.sub.NRi are axial forces borne by an i.sub.th thread on the screw side and the nut side respectively; F is a load value of the planetary roller screw mechanism; Z.sub.R is a number of rollers; and ? indicates a tension and compression state of the screw or the nut, + indicates tension, and ? indicates compression.

[0036] Step 3: iteratively compute an optimal grinding taper angle of roller grinding according to the deformation and force balance equations established in step 2, where a specific computation process is: the grinding taper angle ? of the roller in the deformation and force balance equations in step 2 is gradually increased from 0, and corresponding axial forces F.sub.SRi and F.sub.NRi borne by the thread on the screw side and the nut side may be obtained in the case of any ?; and when loads are most uniformly distributed on the screw side or the nut side, the grinding taper angle ? stops being increased, and the grinding taper angle at a stop moment is recorded as the optimal grinding taper angle ?.sub.opt of roller grinding.

[0037] Through computation, in the embodiment, when the grinding angle is 0.014?, loads are most uniformly distributed on the screw side. Therefore, the optimal grinding taper angle of roller grinding in the embodiment is ?.sub.opt=0.014?.

[0038] Step 4: determine process parameters of roller grinding, where as shown in FIGS. 2-5, the process parameters of roller grinding include a mounting angle ? of a grinding wheel 7 on a machine tool, a rotational speed ?.sub.G of the grinding wheel, a rotational speed ?.sub.R of a machined roller, and an axial movement speed v.sub.G of the grinding wheel; and an axial movement direction of the grinding wheel is a direction determined based on the optimal grinding taper angle ?.sub.opt in step 3.

[0039] The mounting angle ? of the grinding wheel is the same as a helix angle of the machined roller, the rotational speed ?.sub.G of the grinding wheel is determined by a machining capability of a machine tool and characteristics of the grinding wheel, and the rotational speed ?.sub.R of the machined roller and the axial movement speed v.sub.Go of the grinding wheel satisfy a relation of v.sub.G=?.sub.RP.sub.R, and P.sub.R is a thread pitch of the machined roller.

[0040] In the embodiment, the mounting angle of the grinding wheel is ?=2.8?, the rotational speed of the grinding wheel is ?.sub.G=1500 rpm, the rotational speed of the machined roller is ?.sub.R=15 rpm, and the axial movement speed of the grinding wheel is v.sub.G=15 mm/min.

[0041] Step 5: grind a roller taper of the planetary roller screw mechanism by the machine tool according to the process parameters determined in step 4, where as shown in FIG. 6, as the grinding wheel 7 axially moves, a thickness of a thread 8 after roller taper grinding is gradually reduced compared with a thickness of a thread 9 before taper grinding, and a reduction amount reserves a space for the thread to deform under a load. Therefore, according to the roller taper grinding method for a planetary roller screw mechanism provided in the present disclosure, load distribution uniformity of the planetary roller screw mechanism can be effectively improved, and the technical solution has the advantages of low cost, high feasibility, high efficiency, etc.

[0042] Again, the above-mentioned embodiments are only intended to describe the preferred implementation modes of the present disclosure, but not to limit the scope of the present disclosure. Various alterations and improvements made by those of ordinary skill in the art based on the technical solution of the present disclosure without departing from the design spirit of the present disclosure shall fall within the scope of protection determined by the claims of the present disclosure.