Roller taper grinding method for planetary roller screw mechanism
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.
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 wherein the process parameters include an axial movement direction of a grinding wheel which is determined based on the optimal grinding taper angle computed in step 3; 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, wherein the machine tool includes the grinding wheel;
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,
wherein the deformation and force balance equations of the planetary roller screw mechanism established in step 2 are:
{
P
S
+
Δ
l
Si
=
P
R
+
Δ
l
S
Ri
±
P
R
tan
γ
P
N
+
Δ
l
Ni
=
P
R
+
Δ
l
N
Ri
±
P
R
tan
γ
∑
i
=
1
N
t
F
S
Ri
=
F
Z
R
∑
i
=
1
N
t
F
N
Ri
=
F
Z
R
wherein P S , P R and P 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 t , and N t is the number of threads per roller; Δl Si and Δl Ni are axial deformation at an ith segment of the screw and the nut respectively; Δl SRi and Δl NRi are axial deformation of the roller on a screw side and a nut side respectively; γ is a grinding taper angle of the roller; F SRi and F NRi are axial forces borne by an ith thread on the screw side and the nut side respectively; F is a load value of the planetary roller screw mechanism; Z R is the number of rollers; and ± indicates a tension and compression state of the screw or the nut, + indicates tension, and − indicates compression.
2 . The roller taper grinding method for a planetary roller screw mechanism claim 1 , wherein in step 3 of iteratively computing the optimal grinding taper angle according to the deformation and force balance equations established in step 2, the grinding taper angle γ of the roller in the deformation and force balance equations in step 2 is gradually increased from 0, and corresponding axial forces F SRi and F NRi borne by the thread on the screw side and the nut side are capable of being obtained in the case of any γ; and when loads are most uniformly distributed on the screw side or the nut side, the grinding taper angle γ stops being increased, and the grinding taper angle at a stop moment is recorded as the optimal grinding taper angle γ opt of roller grinding.
3 . The roller taper grinding method for a planetary roller screw mechanism according to claim 2 , wherein the process parameters of roller grinding in step 4 comprise a mounting angle λ of the grinding wheel, a rotational speed ω G of the grinding wheel, a rotational speed ω R of a machined roller, and an axial movement speed ν G of the grinding wheel.
4 . The roller taper grinding method for a planetary roller screw mechanism according to claim 3 , wherein in step 4, the mounting angle λ of the grinding wheel is the same as a helix angle of the machined roller, the rotational speed ω G of the grinding wheel is determined by a machining capability of a machine tool and characteristics of the grinding wheel, the rotational speed ω R of the machined roller and the axial movement speed ν G of the grinding wheel satisfy a relation of ν G =ω R P R , and P R is a thread pitch of the machined roller.