External circulation type ball screw

Abstract

The application provides an outer circulation type ball screw, which comprises a screw shaft, a nut sleeve set on the screw shaft, the nut has at least one through hole, the through hole has an open end edge, a backflow assembly is combined with the nut, the backflow assembly has a rotation groove, the rotation groove comprises a rotation section and a continuation section, one end of the rotation section is communicated with the through hole, the other end of the rotation section is connected with the continuation section, one end of the rotation section connected with the through hole has an abutment end edge, the abutment end edge is abutted to the open end edge, the rotation section rotates around a reference point, the outer wall surface of the rotation section is arc-shaped and takes the reference point as the center, the distance between the outer wall surface of the rotation section and the reference point is a rotation radius, the length of the rotation radius is greater than or equal to 1.2 times the ball diameter, the length of the rotation radius is less than or equal to 1.5 times the ball diameter, and the abutment end edge and the open end edge are abutted in a non-tangent manner.

Description

Technical Field

[0001] This invention relates to a ball screw, and more particularly to an external circulation ball screw. Background Technology

[0002] In order to meet the needs of today's automotive and consumer electronics products, ball screws are being developed towards miniaturization. However, in the existing internal circulation return plate design, there is generally a height difference between the nut and the return plate. As a result, when the ball diameter is small, a noticeable jerking sensation will occur.

[0003] For existing tangential external circulation ball screws, please refer to... Figure 1 The device includes a nut 70, a return cover 80 attached to the nut 70, and a plurality of balls 90 that can circulate between the nut 70 and the return cover 80. The nut 70 has two through holes 71, the extension direction of which is defined as a movement direction Z. The return cover 80 has a rotation channel 81 that communicates with the two through holes 71, enabling the balls 90 to achieve a return flow effect. The rotation channel 81 is tangentially connected to the through holes 71, and the rotation channel 81 has a connecting rotation... Section 811 and an extension section 812, because the rotary channel 81 and the through hole 71 are tangentially connected, the rotary section 811 has a large rotation space. Therefore, when the ball 90 enters the rotary section 811 through the through hole 71, the ball 90 will inertially impact the upper edge of the wall 811A of the rotary section 811. This results in a large component of the reaction force along the moving direction Z after the ball 90 impacts the wall 811A of the rotary section 811, causing the front ball 90 to push against the rear ball 90, resulting in the disadvantage of large ball extrusion and impact force. Summary of the Invention

[0004] This invention provides an external circulation ball screw, the main purpose of which is to provide a miniature ball screw that allows for smooth ball flow and avoids ball extrusion problems.

[0005] To achieve the aforementioned objectives, the present invention provides an external circulation ball screw, comprising:

[0006] One screw shaft;

[0007] A nut is fitted onto the screw shaft, and a ball channel is provided between the nut and the screw shaft. The nut has at least one through hole communicating with the ball channel, and the through hole has an open end edge.

[0008] A plurality of balls are arranged in the ball channel in a cyclical manner, and the diameter of the ball is defined as one ball diameter;

[0009] A return assembly is attached to the nut. The return assembly has a rotary groove that communicates with the through hole. The rotary groove has a rotary segment that connects to the through hole. One end of the rotary segment that connects to the through hole has a connecting edge that abuts against an open edge. The connection between the open edge and the connecting edge is non-tangential. The rotary segment rotates around a reference point and corresponds to an outer wall surface. The outer wall surface is arc-shaped and centered on the reference point. The distance between the outer wall surface of the rotary segment and the reference point is a rotation radius. The length of the rotation radius is greater than or equal to 1.2 times the bead diameter and less than or equal to 1.5 times the bead diameter.

[0010] As can be seen from the foregoing, the present invention mainly consists of a length of the radius of rotation that is greater than or equal to 1.2 times the diameter of the ball, a length of the radius of rotation that is less than or equal to 1.5 times the diameter of the ball, and a non-tangential connection between the opening edge and the connecting edge, thereby effectively reducing the problem of ball extrusion caused by uneven ball flow. Attached Figure Description

[0011] Figure 1 The existing technology uses a ball screw whose rotary channel and the through hole are tangentially connected.

[0012] Figure 2 This is an exploded view of the external circulation ball screw of the present invention.

[0013] Figure 3 This is a top view schematic diagram of the external circulation ball screw of the present invention.

[0014] Figure 4 This is a schematic diagram showing the non-tangential connection between the through hole and the rotary groove in this invention.

[0015] Figure 5A The graph shows the impact force data under the condition that the rotary channel and the through hole are connected tangentially in the prior art, with a rotary radius of 0.7 mm. In the graph, each broken line represents the impact force generated by each ball at different time points. The horizontal axis represents time in seconds (S), and the vertical axis represents impact force in Newtons (N).

[0016] Figure 5B The impact force data diagram shows the condition that the existing rotary channel and the through hole are connected tangentially, with a rotary radius of 0.8 mm.

[0017] Figure 5C The impact force data diagram shows the condition that the existing rotary channel and the through hole are connected tangentially, with a rotary radius of 0.9 mm.

[0018] Figure 5DThe impact force data diagram shows the impact force under the condition that the through hole and the rotary groove of the present invention are connected in a non-tangential manner, with a rotation radius of 0.8 mm.

[0019] Figure 5E The impact force data diagram is presented when the through hole and the rotary groove of the present invention are connected in a non-tangential manner, under the condition that the rotation radius is 0.85mm.

[0020] Figure 5F This is a graph showing the impact force data presented when the through hole and the rotary groove of the present invention are connected in a non-tangential manner, under the condition that the rotation radius is 0.9 mm.

[0021] Figure 5G The impact force data diagram is presented when the through hole and the rotary groove of the present invention are connected in a non-tangential manner, under the condition that the rotation radius is 1.0 mm.

[0022] In the diagram, nut-70; through hole-71; return cover-80; rotary channel-81; rotary section-811; wall surface-811A; extension section-812; ball-bearing ball-90; direction of movement-Z; screw shaft-10; external thread groove-11; nut-20; through hole-20A; inner wall-21; internal thread groove-211; outer wall-22; first screw hole-23; through hole-24; open end edge-241; ball-bearing ball. -30; Return assembly -40; Support surface -40A; Rotary groove -41; Rotary section -411; Connecting edge -411A; Outer wall surface -411B; Continuation section -412; Outgoing section -413; Extension -42; Second screw hole -43; Locking component -50; Axis -L; Ball channel -T1; Return path -T2; Reference point -A; Rotation radius -R; Ball diameter -BD; Axial direction -X; Vertical direction -Y. Detailed Implementation

[0023] This invention provides an external circulation ball screw. In one embodiment, please refer to... Figure 2-4 As shown, it includes:

[0024] A screw shaft 10 extends along an axis L, and the outer circumferential surface of the screw shaft 10 has an external threaded groove 11. The axis L defines an axial direction X.

[0025] A nut 20 is fitted onto the screw shaft 10. The nut 20 has a through hole 20A for the screw shaft 10 to pass through. The nut 20 has an inner sidewall 21 and an outer sidewall 22 facing each other. The outer sidewall 22 is flat. The inner sidewall 21 faces the through hole 20A. The inner sidewall 21 has an internal thread groove 211. The internal thread groove 211 corresponds to the external thread groove 11. A ball channel T1 is formed between the internal thread groove 211 and the external thread groove 11. The nut 20 has two first screw holes 23 and two through holes 24. The two screw holes 23 and the two through holes 24 penetrate the outer sidewall 22. The ball channel T1 communicates with the two through holes 24. The two through holes 24 have an open end edge 241 at the point where they penetrate the outer sidewall 22. The extension direction of the through holes 24 is a vertical direction Y.

[0026] A plurality of balls 30 are cyclically disposed in the ball channel T1. The diameter of the ball 30 is defined as a ball diameter BD. In a specific embodiment, the ball diameter BD is between 1.0 mm and 0.4 mm.

[0027] A return assembly 40 is attached to the outer side wall 22 of the nut 20. The return assembly 40 has a bearing surface 40A facing the outer side wall 22. The bearing surface 40A is planar and has a rotary groove 41. The rotary groove 41 and the two through holes 24 together form a return path T2. The return path T2 communicates with the ball channel T1. The rotary groove 41 includes a rotary section 411, a continuous section 412, and a lead-out section 413 connected in sequence. The rotary section 411 communicates with one of the through holes 24, and the lead-out section 413 communicates with the other through hole 24. The rotary section 411 connects to one of the through holes 24. The end has a connecting end edge 411A, which abuts against the opening end edge 241. The other end of the rotating segment 411 connects to the continuation segment 412. The extension direction of the rotating segment 411 includes the components of the axial direction X and the vertical direction Y, so that an outer wall surface 411B corresponding to the rotating segment 411 is arc-shaped. The rotating segment 411 rotates around a reference point A. The outer wall surface 411B is centered on the reference point A. The distance between the outer wall surface 411B and the reference point A is a rotation radius R. The length of the rotation radius R is greater than or equal to 1.2 times the bead diameter BD, and the length of the rotation radius R is less than or equal to 1.5 times the bead diameter BD.

[0028] The connection between the open end edge 241 and the connecting end edge 411A is non-tangential, making the return path T2 a non-tangential path.

[0029] Therefore, since the connecting edge 411A of the rotating section 411 of the rotating groove 41 is connected to the opening edge 241 of the through hole 24 in a non-tangential manner, compared with the existing tangential connection design, under the same rotation radius R, the rotation space of the rotating section 411 of the present invention is smaller, and the position of the ball 30 impacting the outer wall surface 411B of the rotating section 411 is closer to the connecting edge 411A, so that the component of the reaction force of the ball 30 impacting the outer wall surface 411B along the axial direction X is larger. Therefore, the process of the ball 30 in front entering the continuation section 412 along the rotating section 411 is less likely to be pushed by the ball 30 behind, so the impact force is smaller, thereby improving the smoothness of the return flow.

[0030] The reflux assembly 40 also has two second screw holes 43, the positions of which correspond to the positions of the two first screw holes 23 respectively. It also has two locking members 50 that pass through the first screw holes 23 and the second screw holes 43 respectively to lock the reflux assembly 40 to the nut 20.

[0031] Preferably, the reflux assembly 40 further has two extensions 42 extending from the bearing surface 40A, one of which is adjacent to the rotating section 411 and the other is adjacent to the outlet section 413, and the two extensions 42 extend into the two through holes 24 respectively.

[0032] The above describes the configuration of the main components in each embodiment of the present invention. The efficacy of the present invention is explained below:

[0033] The impact force on the rotary channel 81 caused by the ball bearing 90 passing through the existing return cover 80, as simulated by computer, is shown in the figure. Figures 5A to 5C This diagram illustrates the impact force generated when the ball 90 passes through the rotary channel 81, where the rotary channel 81 and the through hole 71 are tangentially connected, and the ball diameter is 0.6 mm. The broken lines in the coordinate system represent the impact force generated by each ball 90 at different time points within the rotary channel 81. The horizontal axis represents time in seconds (s), and the vertical axis represents impact force in Newtons (N). For a rotary radius of 0.7 mm, please refer to... Figure 5A The average impact force of the ball bearing 90 is 13N, and the maximum impact force is 35.37N. When the radius of rotation is 0.8mm, please refer to... Figure 5B The average impact force of ball bearing 90 is 1.5N, and the maximum impact force is 3.09N. When the radius of rotation is 0.9mm, please refer to... Figure 5C The average impact force of the ball bearing 90 is 3.7N, and the maximum impact force of the ball bearing 90 is 6.47N.

[0034] The impact force on the rotary groove 41 caused by the ball bearing 30 passing through the return assembly 40 of the present invention, as simulated by computer, is shown in the figure below. Figures 5D to 5F This diagram illustrates the impact force generated when the ball 30 passes through the rotary groove 41, provided that the through hole 24 and the rotary groove 41 are connected non-tangentially and the ball diameter BD is 0.6 mm. The broken lines in the coordinate system represent the impact force generated by each ball 30 at different time points within the rotary groove 41. The horizontal axis represents time, and the vertical axis represents impact force. For a rotary radius R of 0.8 mm, please refer to... Figure 5D The average impact force of ball bearing 30 is 0.29N, and the maximum impact force is 0.75N. When the radius of rotation R is 0.85mm, please refer to... Figure 5E The average impact force of ball bearing 30 is 0.26N, and the maximum impact force is 0.89N. When the radius of rotation R is 0.9mm, please refer to... Figure 5F The average impact force of ball 30 is 0.38N, and the maximum impact force of ball 30 is 0.66N.

[0035] Please also refer to Figure 5G As shown, when the through hole 24 and the rotary groove 41 are connected in a non-tangential manner and the ball diameter BD is 0.6mm, however, when the rotation radius R is 1.0mm, it is no longer possible to meet the condition that the length of the rotation radius R is less than or equal to 1.5 times the ball diameter BD. Therefore, the test results show that the ball 30 will get stuck and cannot flow back smoothly.

[0036] In summary, when the radii of rotation R are both 0.8 mm, the average impact force of the ball 30 is only 0.29 N when the through hole 24 and the rotary groove 41 are connected in a non-tangential manner, while the average impact force of the ball 90 increases to 1.5 N when the rotary channel 81 and the through hole 71 are connected in a tangential manner. In addition, when the radii of rotation R are both 0.9 mm, the average impact force of the ball 30 is only 0.38 N when the through hole 24 and the rotary groove 41 are connected in a non-tangential manner, while the average impact force of the ball 90 increases to 3.7 N when the rotary channel 81 and the through hole 71 are connected in a tangential manner.

[0037] As can be seen from the foregoing, the present invention mainly consists of a length of the radius of rotation R that is greater than or equal to 1.2 times the diameter of the ball BD, a length of the radius of rotation R that is less than or equal to 1.5 times the diameter of the ball BD, and the connection between the open end edge 241 and the connecting end edge 411A is a non-tangential connection, thereby effectively reducing the problem of ball extrusion caused by the unsmooth flow of the ball 30.

Claims

1. An external circulation ball screw, characterized in that, include: One screw shaft; A nut is fitted onto the screw shaft, and a ball channel is provided between the nut and the screw shaft. The nut has at least one through hole communicating with the ball channel, and the through hole has an open end edge. A plurality of balls are arranged in the ball channel in a cyclical manner, and the diameter of the ball is defined as one ball diameter; A return assembly is installed on the nut. The return assembly has a rotary groove that communicates with the through hole. The rotary groove has a rotary segment that connects with the through hole. One end of the rotary segment that connects with the through hole has a connecting edge that abuts against an open edge. The connection between the open edge and the connecting edge is non-tangential. The rotary segment rotates around a reference point and corresponds to an outer wall surface. The outer wall surface is arc-shaped and has the reference point as its center. The distance between the outer wall surface and the reference point is a rotation radius. The length of the rotation radius is greater than or equal to 1.2 times the diameter of the bead, and the length of the rotation radius is less than or equal to 1.5 times the diameter of the bead.

2. The external circulation ball screw as described in claim 1, characterized in that, The diameter of the bead is between 1.0mm and 0.4mm.

3. The external circulation ball screw as described in claim 1, characterized in that, The rotary groove also includes a continuation section and a lead-out section. The other end of the rotary section that connects to the through hole is connected to the continuation section, and the continuation section is connected to the lead-out section. There are two through holes, and the lead-out section is connected to the other through hole.

4. The external circulation ball screw as described in claim 1, characterized in that, The nut has a through hole for the screw shaft to pass through, the screw shaft has an external threaded groove, the nut has an inner sidewall and an outer sidewall facing each other, the inner sidewall faces the through hole, the inner sidewall has an internal threaded groove corresponding to the external threaded groove, the internal threaded groove and the external threaded groove form the ball channel, the return assembly is attached to the outer sidewall of the nut, and the opening end edge is where the through hole passes through the outer sidewall.

5. The external circulation ball screw as described in claim 1, characterized in that, The nut has two first screw holes, and the reflux assembly has two second screw holes. The positions of the two second screw holes correspond to the positions of the two first screw holes, and two locking members are respectively inserted through the first screw holes and the second screw holes.

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