Rotary ball bearing axle shaft spline set

Abstract

A rotating ball shaft spline assembly includes a shaft, a ball nut, and a ball spline. The ball nut is disposed on the shaft and has a plurality of first balls rolling in threaded rolling grooves. The center of each first ball in the threaded rolling grooves to the shaft center has a first distance. The ball spline is disposed on the shaft. The ball spline includes a spline outer tube and a plurality of second balls rolling in straight rolling grooves. The center of each second ball in the straight rolling grooves to the shaft center has a second distance, which is greater than the first distance. When the spline outer diameter of the ball spline meets the formula condition, the optimal spline outer diameter size can be obtained to effectively reduce the volume of the ball spline and achieve low inertia operation of the rotating ball shaft spline assembly during operation.

Description

Technical Field

[0001] This invention relates to a rotary ball bearing spline assembly, and more particularly to a rotary ball bearing spline assembly capable of operating with low inertia. Background Technology

[0002] Rotary ball bearing spline assemblies are now widely used in high-precision transmission systems, such as robots, CNC machine tools, and automated equipment. Traditional design methods typically adjust the overall dimensions of the ball nuts and ball splines based on rules of thumb. However, this can lead to uneven load distribution or increased frictional losses, thereby affecting product lifespan and accuracy. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide an optimization method based on mathematical calculations to ensure that the rotary ball bearing spline assembly has the best motion performance and to further reduce the volume and weight of the ball nut or ball spline, so as to reduce the inertia generated by the rotary ball bearing spline assembly during operation.

[0004] In one embodiment, the present invention provides a rotary ball bearing spline assembly including a shaft, a ball nut, and a ball spline. The shaft surface is provided with helical threaded grooves and straight linear grooves. The ball nut is disposed on the shaft and has a plurality of first balls rolling in the threaded grooves, with the center of each first ball located in the threaded groove being a first distance from the shaft axis. The ball spline is disposed on the shaft and includes a spline outer cylinder and a plurality of second balls. The plurality of second balls are disposed on the spline outer cylinder and roll in the straight linear grooves, with the center of each second ball located in the straight linear groove being a second distance from the shaft axis, the second distance being greater than the first distance.

[0005] The spline outer diameter of the spline outer cylinder is calculated using the following formula:

[0006]

[0007] Ds is the outer diameter of the spline;

[0008] hs is twice the distance from the center of the second ball to the axis of the spline outer cylinder when the second ball set rolling on the straight rolling groove is set on the spline outer cylinder;

[0009] 'a' is the angle between the first extension line and the second extension line. The first extension line is a virtual straight line from the contact point between the second ball and the linear rolling groove to the center of the second ball. The second extension line is a virtual straight line from the center of the second ball to the axis.

[0010] b is the machining error angle for the straight rolling groove;

[0011] The diameter of the second ball;

[0012] Fs represents the percentage of ball diameter machining error;

[0013] X represents the necessary wall thickness for the splined outer tube.

[0014] Among them, the above-mentioned hs must meet the following rules:

[0015]

[0016] D is the diameter of the shaft.

[0017] The spline outer diameter of the spline outer cylinder obtained by the above formula is the optimal spline outer diameter size under the corresponding shaft diameter and the required load capacity, by limiting the triple height (hs) of the spline to be higher than the triple height of the ball nut. This ensures that the balls transmit the load in the appropriate position, with proper load distribution and motion accuracy, and reduces local stress concentration. At the same time, the obtained optimal spline outer diameter can effectively reduce the volume of the ball spline compared to the past, so as to achieve low inertia operation of the entire rotary ball shaft spline assembly during operation. Due to its low inertia characteristics, it can improve the effects caused by inertia during operation.

[0018] In some embodiments, 'a' is less than 45°.

[0019] In some embodiments, the diameter of the first ball is the same as the diameter of the second ball.

[0020] In some embodiments, the outer diameter of the ball nut is equal to the outer diameter of the spline.

[0021] In some embodiments, the angle of b is approximately 10° to 15°.

[0022] In some embodiments, the value of X is greater than 0.3 mm.

[0023] In some embodiments, the value of Fs is 5%.

[0024] In some embodiments, the ball spline of the rotary ball shaft spline assembly further includes a bearing outer sleeve fitted onto the outer surface of the spline outer cylinder, and a second ball is provided between the bearing outer sleeve and the spline outer cylinder. The outer diameter of the bearing outer sleeve is calculated using the following formula:

[0025]

[0026] Rs is the outer diameter of the outer casing.

[0027] In some embodiments, the inner diameter of the ball spline is calculated using the following formula:

[0028]

[0029] ds is the inner diameter of the spline.

[0030] In another embodiment, the present invention provides a rotary ball bearing spline assembly including a shaft, a ball nut, and a ball spline. The shaft surface is provided with helical threaded rolling grooves and straight linear rolling grooves. The ball nut is disposed on the shaft and has a plurality of first balls rolling in the threaded rolling grooves, with a first distance between the center of each first ball located in the threaded rolling groove and the axis of the shaft. The ball spline is disposed on the shaft and includes a spline outer cylinder and a plurality of second balls. The plurality of second balls are disposed on the spline outer cylinder and roll in the straight rolling grooves, with a second distance between the center of each second ball located in the straight rolling groove and the axis of the shaft, the second distance being greater than the first distance.

[0031] The spline inner diameter of the spline outer cylinder is calculated using the following formula:

[0032]

[0033] ds is the inner diameter of the spline;

[0034] hs is twice the distance from the center of the second ball to the axis of the spline outer cylinder when the second ball set rolling on the straight rolling groove is set on the spline outer cylinder;

[0035] The diameter of the second ball.

[0036] Among them, hs must meet the following rules:

[0037]

[0038] D is the diameter of the shaft;

[0039] 'a' is the angle between the first extension line and the second extension line. The first extension line is a virtual straight line from the contact point between the second ball and the linear rolling groove to the center of the second ball. The second extension line is a virtual straight line from the center of the second ball to the axis.

[0040] b is the machining error angle for the straight rolling groove.

[0041] The spline inner diameter of the spline outer cylinder, obtained through the above formula, corresponds to the shaft diameter and the required load. By limiting the triple height (hs) of the spline to be higher than that of the ball nut, the optimal spline outer diameter can be obtained. This ensures that the balls transmit the load in the appropriate position, resulting in proper load distribution and motion accuracy, and reduces local stress concentration. Simultaneously, the obtained optimal spline inner diameter effectively reduces the weight of the ball spline compared to previous methods, enabling the rotary ball shaft spline assembly to operate with low inertia during operation. This low inertia characteristic mitigates the effects caused by inertia during operation.

[0042] In some embodiments, α is less than 45°.

[0043] In some embodiments, the diameter of the first ball is the same as the diameter of the second ball.

[0044] In some embodiments, the angle of b is approximately 10° to 15°. Attached Figure Description

[0045] Figure 1 A perspective view of a rotary ball bearing shaft spline assembly according to an embodiment of the present invention.

[0046] Figure 2 A cross-sectional view of a rotary ball bearing spline assembly according to an embodiment of the present invention.

[0047] Figure 3 A cross-sectional view of the shaft and the second ball bearing according to an embodiment of the present invention.

[0048] Figure 4 A cross-sectional view of the outer cylinder of a ball spline according to an embodiment of the present invention.

[0049] Among them, the attached reference numerals

[0050] 100: Rotary ball bearing spline assembly

[0051] 10: Shaft

[0052] 11: Threaded rolling groove

[0053] 12: Linear rolling groove

[0054] 20: Ball bearing nut

[0055] 21: First ball bearing

[0056] 30: Ball spline

[0057] 31:Spline outer barrel

[0058] 32: Second ball bearing

[0059] 33: Bearing outer sleeve

[0060] a: included angle

[0061] b: Machining error angle of straight rolling groove

[0062] C: Axis

[0063] d1: First distance

[0064] d2: Second distance

[0065] D: Shaft diameter

[0066] Ds: Spline outer diameter

[0067] ds: spline inner diameter

[0068] hs: When the second ball set rolling in the linear rolling groove is installed on the splined outer cylinder, the distance from the center of the second ball to the axis of the splined outer cylinder is twice the distance between the center of the second ball and the axis of the splined outer cylinder.

[0069] L1: First extension line

[0070] L2: Second extension line

[0071] Rs: Outer diameter of the outer jacket

[0072] X: Must be thick-skinned

[0073] diameter Detailed Implementation

[0074] Please see Figure 1 and Figure 2 , Figure 1 A perspective view of a rotary ball bearing spline assembly according to an embodiment of the present invention. Figure 2 A cross-sectional view of a rotary ball bearing spline assembly according to an embodiment of the present invention. The rotary ball bearing spline assembly 100 of this embodiment includes a shaft 10, a ball nut 20, and a ball spline 30. The shaft 10 has helical threaded grooves 11 and straight linear grooves 12 on its surface. The ball nut 20 is disposed on the shaft 10 and has a plurality of first balls 21 rolling in the threaded grooves 11. The center of each first ball 21 located in the threaded groove 11 is at a first distance d1 from the axis C of the shaft 10.

[0075] A ball spline 30 is mounted on the shaft 10. The ball spline 30 includes a spline outer cylinder 31 and a plurality of second balls 32. The plurality of second balls 32 are mounted on the spline outer cylinder 31 and roll in a linear rolling groove 12. The center of each second ball 32 located in the linear rolling groove 12 has a second distance d2 from the axis C of the shaft 10. The second distance d2 is greater than the first distance d1. Here, the first distance d1 can be regarded as half of the three-line height of the ball nut 20, and the second distance d2 can be regarded as half of the three-line height of the ball spline 30. By making the second distance d2 greater than the first distance d1, the three-line height of the ball spline 30 is made higher than the three-line height of the ball nut 20, thereby adjusting the contact angle and position between the ball spline 30 and the shaft 10, ensuring that the second balls 32 transmit load in the appropriate position, thus achieving appropriate load distribution and motion accuracy, and reducing local stress concentration.

[0076] Please refer to the following at the same time. Figure 3 and Figure 4 , Figure 3 A cross-sectional view of the shaft and the second ball bearing according to an embodiment of the present invention. Figure 4 A cross-sectional view of the spline outer cylinder of a ball spline according to an embodiment of the present invention. In this embodiment, the calculation of the spline outer diameter Ds of the spline outer cylinder 31 will be performed using... Figures 1 to 4 The spline outer diameter Ds of the spline outer cylinder 31 is calculated using the following formula:

[0077]

[0078] Ds is the outer diameter of the spline;

[0079] hs is twice the distance from the center of the second ball 32 to the axis of the spline outer cylinder 31 when the second ball 32 set rolling on the straight rolling groove 12 is provided on the spline outer cylinder 31.

[0080] 'a' is the angle between the first extension line L1 and the second extension line L2. The first extension line L1 is a virtual straight line from the contact point between the second ball 32 and the linear rolling groove 12 to the center of the second ball 32. The second extension line L2 is a virtual straight line from the center of the second ball 32 to the shortest distance from the axis C.

[0081] b is the machining error angle for the straight rolling groove;

[0082] The diameter of the second ball 32;

[0083] Fs represents the percentage of ball diameter machining error;

[0084] X represents the necessary wall thickness of the splined outer tube 31.

[0085] Depend on Figure 4 It can be seen that the outermost diameter of the spline outer cylinder 31 is the outer diameter of the spline, Ds. Figure 3 The diagram shows a cross-sectional view of the shaft 10, with the second ball 32 located in the linear rolling groove 12 indicated by dashed lines. Figure 3 The diameter of the circle indicated by the line connecting the two points is the value of hs. The circle indicated by the line connecting the two points is the location of the center of the second ball 32, which is mounted on the spline outer cylinder 31 and will roll in the linear rolling groove 12. Since the linear rolling groove 12 is arranged parallel to the upper and lower symmetrical sides of the shaft 10, the circle indicated by the line connecting the two points will also pass through the center of the second ball 32 rolling in the upper and lower linear rolling grooves 12 respectively. hs refers to the diameter of the circle indicated by the line connecting the two points, and can be regarded as the height of the three lines of the ball spline 30, which is approximately twice the second distance d2, that is, twice the distance from the center of the second ball 32 to the axis C of the spline outer cylinder 31.

[0086] Continue by Figure 3 As can be seen, 'a' refers to the angle (in degrees) and is the angle between the first extension line L1 and the second extension line L2. The first extension line L1 is a virtual straight line from the contact point between the second ball 32 and the linear rolling groove 12 to the center of the second ball 32. The second extension line L2 is a virtual straight line representing the shortest distance from the center of the second ball 32 to the axis C.

[0087] In this embodiment, the arc surface of the linear rolling groove 12 is different from the arc surface of the second ball 32, and the second ball 32 will contact the arc surface of the linear rolling groove 12 at two points on the circle, so there are two contact points. Figure 3 The diagram only illustrates a virtual straight line from the contact point between the second ball 32 and the left side of the linear rolling groove 12 to the center of the second ball 32, i.e., the first extension line L1. In reality, the second ball 32 also has a contact point with the linear rolling groove 12 on the right side. The angle between this contact point and the virtual straight line from the center of the second ball 32 to the second extension line L2 will be the same as the angle α between the first extension line L1 and the second extension line L2. Furthermore, it should be noted that... Figure 3 Due to the size ratio of the drawing, it may be visually misleading to believe that the entire arc surface of the second ball 32 is in contact with the straight rolling groove 12, but in reality, it is only a two-point contact.

[0088] Furthermore, in order to meet the aforementioned condition that the second distance d2 is greater than the first distance d1, and to ensure that the contact point of the ball spline 30 is higher than the contact point of the ball nut 20, and for ease of calculation, when the angle corresponding to 'a' on the ball nut 20 is set to 45°, the angle 'a' of the ball spline 30 is often less than 45°. The specific angle to be used is usually determined by referring to a table based on the diameter D of the shaft 10 and the required load of the rotary ball shaft spline assembly 100.

[0089] b is the machining error angle of the straight rolling groove (in degrees). This error occurs during the machining of the straight rolling groove 12 due to potential machining errors, causing an error in the angle α between the first extension line L1 and the second extension line L2. This machining error angle b must be included in the calculation of the spline outer diameter Ds. Furthermore, depending on the machining method and precision, this error may occur simultaneously on both sides. The machining error angle b of the straight rolling groove defined here is as follows: Figure 3 As shown, this refers to the error angle on one side (left side of the figure). In this embodiment, the preferred range for the machining error angle b of the straight rolling groove is 10° to 15°.

[0090] The second ball bearing 32 may also experience machining errors during manufacturing. To ensure a more accurate and effective spline outer diameter Ds while still allowing the second ball bearing 32 to roll smoothly, the percentage of machining error Fs in the ball diameter of the second ball bearing 32 is taken into account when calculating the spline outer diameter Ds. In this embodiment, this percentage of machining error Fs is 5%. In other embodiments, the percentage of machining error Fs in the ball diameter can be adjusted depending on the machining accuracy to make the calculated spline outer diameter Ds more consistent with actual requirements.

[0091] During the manufacturing process of the spline outer cylinder 31, in order to meet the required structural strength and considering machining tolerances, a necessary wall thickness X needs to be formed outward from the ball channel where the second ball 32 is located to avoid affecting the structural strength. The aforementioned necessary wall thickness X is the minimum wall thickness required based on the currently achievable machining tolerances. In this embodiment, the value of the necessary wall thickness X is greater than 0.3 mm.

[0092] To minimize the calculated spline outer diameter Ds, the size of the spline outer cylinder 31 should be minimized, thereby reducing the overall volume of the ball spline 30 and ultimately lowering operational inertia. hs must conform to the following rules:

[0093]

[0094] Where D is the diameter of shaft 10.

[0095] The spline outer diameter Ds of the spline outer cylinder 31 obtained by the above formula, under the corresponding diameter D of the shaft 10 and the required load that the rotary ball shaft spline assembly 100 can withstand, is optimized by limiting the second distance d2 of the ball spline 30 to be greater than the first distance d1. This means that the triaxial height of the ball spline 30 is higher than the triaxial height of the ball nut 20, thus obtaining the optimal spline outer diameter Ds. Therefore, the ball spline 30 manufactured with the obtained optimal spline outer diameter Ds can effectively reduce the volume of the ball spline 30 compared to the past, achieving low inertia operation of the rotary ball shaft spline assembly 100 as a whole during operation. Furthermore, due to its low inertia characteristics, the effects caused by inertia during operation can be improved.

[0096] To verify the above effects, an inertial analysis was performed on the splined outer cylinder 31 of Example 1 and a conventional splined outer cylinder as a comparative example under the same operating conditions using a simulation method. The relevant analysis data results are shown in Table 1 below.

[0097] Table 1

[0098] Example 1 Comparative example Spline outer diameter Ds (cm) 3.25 3.6 Weight (kg) of Ball Spline 30 0.251 0.37 <![CDATA[Inertia of rotary ball screw spline set 100 (kg×cm 2 )]]> 0.7163 1.086

[0099] As shown in the table above, under the same conditions of the size of the second ball 32, the diameter D of the shaft 10, and the required load that the rotary ball bearing spline assembly 100 can withstand, the spline outer diameter Ds under the condition of hs is calculated by substituting the corresponding condition values ​​into the aforementioned formula, resulting in a spline outer diameter Ds of 3.25 cm. This spline outer diameter Ds is significantly smaller than the existing (i.e., comparative example) 3.6 cm. With the effective reduction of the spline outer diameter Ds, the overall volume is reduced, which also reduces the weight of the ball spline 30. The combined effect of reduced volume and weight effectively decreases the inertia of the rotary ball bearing spline assembly 100 during operation. Compared to the rotary ball bearing spline assembly of the comparative example, the rotary ball bearing spline assembly 100 of Embodiment 1, due to its low inertia characteristics, can improve the effects caused by inertia during operation.

[0100] Furthermore, under the above conditions, in order to ensure the consistency of movement of all balls in the rotary ball bearing spline assembly 100 and to avoid additional friction and stress caused by balls of different diameters, the diameter of the first ball 21 and the diameter of the second ball 32 can be the same.

[0101] Furthermore, after determining the spline outer diameter Ds using the aforementioned formula and conditions, the outer diameter of the ball nut 20 can be made equal to the spline outer diameter Ds. This makes the post-installation planning of the entire rotary ball shaft spline assembly 100 more convenient, eliminating the need to design and manufacture corresponding components for the ball nut 20 and the ball spline 30 respectively, based on their respective outer diameters.

[0102] Depend on Figure 1 and Figure 2 As can be seen, in this embodiment, the ball spline 30 further includes a bearing outer sleeve 33, which is fitted onto the outer surface of the spline outer cylinder 31, and a plurality of second balls 32 are provided between the bearing outer sleeve 33 and the spline outer cylinder 31. Since the bearing outer sleeve 33 is assembled on the spline outer cylinder 31, and the two are connected by a plurality of second balls 32, in order to ensure that the bearing outer sleeve 33 also has a corresponding optimal outer sleeve diameter Rs, the outer sleeve diameter Rs of the bearing outer sleeve 33 is calculated by the following formula:

[0103]

[0104] Rs is the outer diameter of the outer casing.

[0105] Depend on Figure 2 As can be seen, the outer diameter Rs of the bearing outer sleeve 33 refers to the diameter of the bearing outer sleeve 33. Since the bearing outer sleeve 33 is fitted over the spline outer sleeve 31, and a second ball 32 is sandwiched between them, the outer diameter Rs is based on the spline outer diameter Ds, but is further increased by the diameter of the second ball 32. The percentage error Fs in the ball diameter machining of the second ball 32 is also taken into account. Furthermore, by adding the same necessary wall thickness X to the spline outer cylinder 31, the calculation formula for the outer casing outer diameter Rs can be obtained. Since the outer casing outer diameter Rs is obtained by matching the spline outer diameter Ds of the spline outer cylinder 31, the outer casing outer diameter Rs can effectively reduce its volume, saving material required for manufacturing the bearing outer casing 33 and effectively reducing manufacturing costs.

[0106] In addition to effectively reducing the volume of the spline outer cylinder 31 by calculating the spline outer diameter Ds, thereby reducing the inertia of the rotary ball bearing spline assembly 100, the spline inner diameter ds of the ball spline 30 can also be calculated using the following formula:

[0107]

[0108] ds is the inner diameter of the spline.

[0109] The inner diameter ds of the spline is the inner diameter of the ball spline 30. The inner diameter ds calculated using the above formula is the optimal inner diameter ds that can be obtained under the condition of matching the outer diameter Ds of the spline. By calculating the optimal inner diameter ds, the overall weight of the ball spline 30 can be further reduced, thereby reducing the inertia of the rotary ball shaft spline assembly 100.

[0110] Similarly, to verify the effect of simultaneously changing the spline outer diameter Ds and the spline inner diameter ds, an inertial analysis was performed on the spline outer cylinder 31 of Example 2 and the existing spline outer cylinder as a comparative example under the same operating conditions using a simulation method. The relevant analysis data results are shown in Table 2 below.

[0111] Table 2

[0112] Example 2 Comparative example Spline outer diameter Ds (cm) 3.25 3.6 Spline inner diameter ds (cm) 1.7 1.61 Weight of ball spline (kg) 0.247 0.37 <![CDATA[Inertia of rotary ball screw spline set 100 (kg×cm 2 )]]> 0.686 1.086

[0113] As shown in the table above, when the dimensions of the second ball 32, the diameter D of the shaft 10, and the required load that the rotary ball shaft spline assembly 100 can withstand are all the same, substituting the corresponding conditional values ​​into the aforementioned formula to calculate the spline outer diameter Ds and spline inner diameter ds values ​​that meet the conditions hs, we can obtain that the spline outer diameter Ds is 3.25 cm and the spline inner diameter ds is 1.7 cm. Except that the spline outer diameter Ds is significantly smaller than the current (i.e., comparative example) 3.6 cm, the spline inner diameter ds is larger than the current (i.e., comparative example) 1.61 cm. With changes in both the spline outer diameter Ds and the spline inner diameter ds, the overall volume is further reduced, resulting in a corresponding reduction in the weight of the ball spline 30. The combined effect of reduced volume and weight more effectively decreases the moment of inertia of the rotary ball shaft spline assembly 100 during operation. Compared to the rotary ball bearing spline assembly of the comparative example, the rotary ball bearing spline assembly of Example 2 has low inertia characteristics, which can improve the effects caused by inertia during operation.

[0114] As explained above, reducing the volume and weight of the ball spline 30 can reduce the inertia of the rotary ball shaft spline assembly 100 during operation. In Embodiment 1, the outer diameter Ds of the spline was changed, while in Embodiment 2, both the outer diameter Ds and the inner diameter ds of the spline were changed. However, in another embodiment, the volume and weight of the ball spline 30 can be reduced by only changing the inner diameter ds, thereby achieving the effect of reducing the inertia of the rotary ball shaft spline assembly 100 during operation.

[0115] In the aforementioned rotary ball bearing spline assembly 100, in embodiment 3, the second distance d2 is also set to be greater than the first distance d1, and a is set to be less than 45°. The diameters of the first ball 21 and the second ball 32 are... The same applies, and the angle of b is approximately 10° to 15°. The spline inner diameter ds is then calculated using the following formula:

[0116]

[0117] ds is the inner diameter of the spline.

[0118] It should be noted that when calculating the spline inner diameter ds, hs must also meet the following rules:

[0119]

[0120] D is the diameter of shaft 10;

[0121] 'a' is the angle between the first extension line L1 and the second extension line L2. The first extension line L1 is a virtual straight line from the contact point between the second ball 32 and the linear rolling groove 12 to the center of the second ball 32. The second extension line L2 is a virtual straight line from the center of the second ball 32 to the shortest distance from the axis C.

[0122] b is the machining error angle for the straight rolling groove.

[0123] To verify the above effects, an inertial analysis was conducted on the splined outer cylinder 31 of Example 3 and a conventional splined outer cylinder as a comparative example under the same operating conditions using a simulation method. The relevant analysis data results are shown in Table 3 below.

[0124] Table 3

[0125] Example 3 Comparative example Spline inner diameter ds (cm) 1.7 1.61 Weight (kg) of Ball Spline 30 0.356 0.37 <![CDATA[Inertia of rotary ball screw spline set 100 (kg×cm 2 )]]> 1.0372 1.086

[0126] As shown in the table above, under the same conditions of the size of the second ball 32, the diameter D of the shaft 10, the required load that the rotary ball bearing spline assembly 100 can withstand, and the outer diameter Ds of the spline, the spline inner diameter ds value under the condition hs is calculated by substituting the corresponding condition values ​​into the aforementioned formula. The result is a spline inner diameter ds of 1.7 cm. This spline inner diameter ds is slightly larger than the current (i.e., comparative example) 1.61 cm. With a slightly larger spline inner diameter ds, the total wall thickness of the ball spline 30 can be slightly reduced, and the weight of the ball spline 30 will be correspondingly reduced. This weight reduction also reduces the inertia of the rotary ball bearing spline assembly 100 during operation. Compared to the rotary ball bearing spline assembly of the comparative example, the rotary ball bearing spline assembly 100 of Embodiment 3, due to its low inertia characteristics, can improve the effects caused by inertia during operation.

[0127] Although the present invention has been disclosed above with reference to the foregoing embodiments, it is not intended to limit the present invention. Any person skilled in the art may make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of patent protection of the present invention shall be determined by the scope of the claims appended to this specification.

Claims

1. A rotary ball bearing spline assembly, characterized in that, include: A shaft has a spiral-shaped threaded groove and a straight-line rolling groove on its surface; A ball bearing nut is disposed on the shaft and has a plurality of first balls rolling in the threaded groove, wherein the center of each of the first balls located in the threaded groove is at a first distance from an axis of the shaft; and A ball spline is disposed on the shaft. The ball spline includes a spline outer cylinder and a plurality of second balls. The second balls are disposed on the spline outer cylinder and roll in a linear rolling groove. The center of each of the second balls located in the linear rolling groove has a second distance from the axis of the shaft. The second distance is greater than a first distance. The outer diameter of the spline outer cylinder is calculated by the following formula: Ds is the outer diameter of the spline; hs is twice the distance from the center of the second ball to the axis of the spline outer cylinder when the second ball set rolling on the straight rolling groove is provided on the spline outer cylinder; 'a' is the angle between a first extension line and a second extension line. The first extension line is a virtual straight line from the contact point between the second ball and the straight rolling groove to the center of the second ball. The second extension line is a virtual straight line from the center of the second ball to the axis. b is the machining error angle of the straight rolling groove; The diameter of the second ball; Fs represents the percentage of ball diameter machining error; and X represents the required wall thickness of the splined outer cylinder; Among them, hs must meet the following rules: D is the diameter of the shaft.

2. The rotary ball bearing spline assembly as described in claim 1, characterized in that, a is less than 45°.

3. The rotary ball bearing spline assembly as described in claim 1, characterized in that, The diameter of the first ball is the same as the diameter of the second ball.

4. The rotary ball bearing spline assembly as described in claim 1, characterized in that, The outer diameter of the ball bearing nut is equal to the outer diameter of the spline.

5. The rotary ball bearing spline assembly as described in claim 1, characterized in that, The angle of b is approximately 10° to 15°.

6. The rotary ball bearing spline assembly as described in claim 1, characterized in that, The value of X is greater than 0.3 mm.

7. The rotary ball bearing spline assembly as described in claim 1, characterized in that, The value of Fs is 5%.

8. The rotary ball bearing spline assembly as described in claim 1, characterized in that, The ball spline further includes a bearing outer sleeve fitted onto the outer surface of the spline outer cylinder, and the second balls are located between the bearing outer sleeve and the spline outer cylinder. The outer diameter of the bearing outer sleeve is calculated using the following formula: Rs is the outer diameter of the jacket.

9. The rotary ball bearing spline assembly as described in claim 1, characterized in that, The inner diameter of one spline of the ball spline is calculated using the following formula: ds is the inner diameter of the spline.

10. A rotary ball bearing spline assembly, characterized in that, include: A shaft has a spiral-shaped threaded groove and a straight-line rolling groove on its surface; A ball bearing nut is disposed on the shaft and has a plurality of first balls rolling in the threaded groove, wherein the center of each of the first balls located in the threaded groove is at a first distance from an axis of the shaft; and A ball spline is disposed on the shaft. The ball spline includes a spline outer cylinder and a plurality of second balls. The second balls are disposed on the spline outer cylinder and roll in a linear rolling groove. The center of each of the second balls located in the linear rolling groove has a second distance from the axis of the shaft. The second distance is greater than a first distance. The inner diameter of the spline outer cylinder is calculated by the following formula: ds is the inner diameter of the spline; hs is twice the distance from the center of the second ball to the axis of the splined outer cylinder when the second ball assembly rolling on the linear rolling groove is disposed on the splined outer cylinder; and The diameter of the second ball; Among them, hs must meet the following rules: D is the diameter of the shaft; 'a' is the angle between a first extension line and a second extension line. The first extension line is a virtual straight line from the contact point between the second ball and the straight rolling groove to the center of the second ball. The second extension line is a virtual straight line from the center of the second ball to the axis. b is the machining error angle of the straight rolling groove.

11. The rotary ball bearing spline assembly as described in claim 10, characterized in that, a is less than 45°.

12. The rotary ball bearing spline assembly as described in claim 10, characterized in that, The diameter of the first ball is the same as the diameter of the second ball.

13. The rotary ball bearing spline assembly as described in claim 10, characterized in that, The angle of b is approximately 10° to 15°.

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