US 2026/0298318 A1Published application

Rotary ball screw spline assembly

AssigneeTbi Motion Technology Co., Ltd.

InventorChun-Chan Ko

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Abstract

A rotary ball screw spline assembly includes a shaft, a ball nut and a ball spline. The ball nut and the ball spline are arranged on the shaft. The ball nut has a plurality of first balls rolling on a thread rolling groove. A first distance is provided between the center of each first ball and an axis of the shaft. The ball spline includes a spline outer cylinder and a plurality of second balls arranged on the spline outer cylinder and rolling on a linear rolling groove. A second distance is provided between the center of each second ball and the axis of the shaft, and the second distance is greater than the first distance. When the spline outer diameter of the ball spline meets a specific formula, the optimal spline outer diameter of the ball spline can be obtained to effectively reduce the volume of the ball spline.

Claims13

Dependent claims

A rotary ball screw spline assembly, comprising:

a shaft, wherein a surface of the shaft is provided with a spiral thread rolling groove and a straight linear rolling groove;
a ball nut, arranged on the shaft and having a plurality of first balls rolling on the thread rolling groove, wherein a first distance is provided between a center of each first ball located in the thread rolling groove and an axis of the shaft;
and
a ball spline, arranged on the shaft, wherein the ball spline comprises a spline outer cylinder and a plurality of second balls, the second balls are arranged on the spline outer cylinder and roll on the linear rolling groove, a second distance is provided between a center of each second ball located in the linear rolling groove and the axis of the shaft, the second distance is greater than the first distance, and a spline outer diameter of the spline outer cylinder is calculated by the following formula:
D
⁢
s
=
2
⁢
(
h
⁢
s
2
⁢
cos
⁢
(
a
+
b
)
+
∅
×
F
⁢
s
2
+
X
)
Ds is the spline outer diameter;
hs is twice a distance between the center of the second ball and an axis of the spline outer cylinder when the second ball rolling on the linear rolling groove is assembled on the spline outer cylinder;
a is an included angle between a first extension line and a second extension line, the first extension line is an imaginary straight line from a contact point between the second ball and the linear rolling groove to the center of the second ball, and the second extension line is an imaginary straight line with the shortest distance between the center of the second ball and the axis;
b is a machining error angle of the linear rolling groove;
Ø is a diameter of the second ball;
Fs is a ball diameter machining error percentage;
and
X is a necessary wall thickness of the spline outer cylinder;
wherein hs meets the following rules:
h
⁢
s
>
D
+
2
×
(
cos
⁢
(
a
+
b
)
×
∅
2
)
D is a diameter of the shaft.

60 more elements

A rotary ball screw spline assembly, comprising:

a shaft, wherein a surface of the shaft is provided with a spiral thread rolling groove and a straight linear rolling groove;
a ball nut, arranged on the shaft and having a plurality of first balls rolling on the thread rolling groove, wherein a first distance is provided between a center of each first ball located in the thread rolling groove and an axis of the shaft;
and
a ball spline, arranged on the shaft, wherein the ball spline comprises a spline outer cylinder and a plurality of second balls, the second balls are arranged on the spline outer cylinder and roll on the linear rolling groove, a second distance is provided between a center of each second ball located in the linear rolling groove and the axis of the shaft, the second distance is greater than the first distance, and a spline inner diameter of the spline outer cylinder is calculated by the following formula:
ds
=
2
⁢
(
(
h
⁢
s
2
-
sin
⁢
(
∅
×
1
⁢
8
⁢
0
2
×
π
)
)
2
+
(
∅
2
×
cos
⁢
(
∅
×
1
⁢
8
⁢
0
2
×
π
)
)
2
)
ds is the spline inner diameter;
hs is twice a distance between the center of the second ball and an axis of the spline outer cylinder when the second ball rolling on the linear rolling groove is assembled on the spline outer cylinder;
and
Ø is a diameter of the second ball;
wherein hs meets the following rules:
h
⁢
s
>
D
+
2
×
(
cos
⁢
(
a
+
b
)
×
∅
2
)
D is a diameter of the shaft;
a is an included angle between a first extension line and a second extension line, the first extension line is an imaginary straight line from a contact point between the second ball and the linear rolling groove to the center of the second ball, and the second extension line is an imaginary straight line with the shortest distance between the center of the second ball and the axis;
and
b is a machining error angle of the linear rolling groove.

79 more elements

Dependencies are inferred from the claim text.