Ball screw assembly with inverted nut

Abstract

The invention relates to a nut-inverted ball screw pair which comprises a ball nut and a ball screw axially moving relative to the ball nut, six nut spiral raceways are arranged on the inner wall of the ball nut, and correspondingly, six screw spiral raceways are arranged on the outer wall of the ball screw. The nut spiral raceways and the lead screw spiral raceways are matched one by one to form six spiral raceways; the ball screw is internally provided with six backflow channels arranged in the axial direction in a penetrating mode, and the backflow channels are evenly distributed in the circumferential direction of the ball screw. The six spiral raceways and the backflow channels are in one-to-one correspondence and are respectively divided into two groups which are arranged at intervals; the two ends of the ball screw are each provided with a returner, and the returners are internally provided with a corresponding number of return channels which are communicated with the corresponding spiral raceways and the corresponding backflow channels respectively. A circulation channel is defined by the spiral raceway, the backflow channel and the corresponding return channel of each group, and the two circulation channels are not communicated with each other and are respectively provided with a ball circulation chain; the ball screw pair has the characteristics of high bearing capacity and compact design.

Description

Technical Field

[0001] The present invention relates to an inverted nut ball screw pair, belonging to the technical field of ball screw pairs. Background Art

[0002] A ball screw pair is a device that drives a nut to move linearly by rotating the screw, and is commonly used in the fields of transmission and positioning. While an inverted nut ball screw pair drives the screw to move linearly by rotating the nut, with the driving method being opposite, and is commonly used in occasions where space is limited.

[0003] Currently, most inverted screw pairs adopt planetary screw pairs. Planetary screw pairs are used in the joint drive structures of humanoid robots due to their high load-bearing capacity, high-speed performance, high precision, and compact design. For example, the planetary roller screw pair and its assembly tooling disclosed in Patent CN202311218674.4 use planetary rollers for the transmission between the nut and the screw, and the planetary rollers move along with the screw. However, the inverted planetary roller screw pair consists of multiple small planetary rollers, which has high processing difficulty and a long production cycle, seriously hindering the development of inverted screw pairs. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the present invention provides an inverted nut ball screw pair with high load-bearing capacity.

[0005] To achieve the above object, the technical solution proposed by the present invention is: an inverted nut ball screw pair, including a ball nut and a ball screw that moves axially relative to the ball nut; the inner wall of the ball nut is provided with no less than four even-numbered nut spiral raceways. Correspondingly, the outer wall of the ball screw is provided with the same number of screw spiral raceways, and the nut spiral raceways and the screw spiral raceways are in one-to-one cooperation to form the corresponding number of spiral raceways; The ball screw is provided with the corresponding number of return channels that penetrate axially, and the return channels are evenly distributed along the circumferential direction of the ball screw; the corresponding number of spiral raceways and return channels are in one-to-one correspondence and are respectively divided into two groups arranged at intervals; A returner is respectively provided at both ends of the ball screw, and the returner is provided with the corresponding number of return channels that respectively communicate with the corresponding spiral raceways and return channels; Each group of spiral raceways, return channels, and the corresponding return channels form a circulation channel, and the two circulation channels are not connected to each other and are respectively provided with a ball circulation chain.

[0006] A preferred solution of the above technical solution is: six spiral raceways are provided.

[0007] A further design of the above technical solution is as follows: Six ball inlets / outs are provided along the circumference of the edge of the returner, which are respectively communicated with six spiral raceways. Six ball outlets / ins are provided along the circumference of one side of the returner, which are respectively communicated with six return channels. The six ball inlets / outs and the six ball outlets / ins correspond one by one and are respectively communicated through a return channel.

[0008] A ball stopper is provided for each spiral raceway corresponding to the returner.

[0009] One end of the ball screw shaft is provided with a screw drive rod. The returner at this end is sleeved on the screw drive rod, and a through hole for the screw drive rod to pass through is provided at the center of the returner.

[0010] Six returner threaded holes are provided along the circumference of one side of the returner, and the six returner threaded holes are arranged at intervals with the six ball outlets / ins; Screw threaded holes are provided at both ends of the ball screw corresponding to the returner threaded holes.

[0011] The phase angle between the two ball circulation chains is 60 degrees. For the phase angles between the two groups of nut spiral raceways and the two groups of screw spiral raceways, at least one of them is 60 degrees, and the other is 59 to 61 degrees.

[0012] The beneficial effects of the present invention are as follows: The nut-inverted ball screw pair of the present invention uses balls as rolling elements, has the advantages of high integration and miniaturization, etc. At the same time, both ball circulation chains are multi-start thread structures, effectively enhancing the load-bearing capacity; The overall structure of the ball screw pair, the structures of each part, and the circulation chain structure are all evenly distributed in space, ensuring the balance during loading, making the transmission stable, capable of achieving high-speed and high-precision movement, and the components are simple in composition, easy to install, and have strong machinability. Compared with the reverse planetary screw pair, it can better meet the driving structure requirements of humanoid robots. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a three-dimensional structure schematic diagram of the present invention; Figure 2 is Figure 1 a quarter cross-sectional view of Figure 3 is Figure 1 a cross-sectional view of Figure 4 is Figure 1 an exploded view of Figure 5 is a schematic diagram of the reverse screw unit assembly; Figure 6 is an axonometric view of the reverse ball screw; Figure 7 is a front view of the reverse ball screw; Figure 8 Rear view of reverse ball screw Figure 9 Cross-sectional view of reverse ball screw Figure 10 Axonometric view of reverse ball nut Figure 11 Front view of reverse ball nut Figure 12 Cross-sectional view of reverse ball nut Figure 13 Axonometric view of ball returner Figure 14 Front view of ball returner Figure 15 Side view of ball returner Figure 16 Rear view of ball returner Figure 17 Axonometric view of ball circulation chain assembly Figure 18 Front view of ball circulation chain assembly Figure 19 Side view of ball circulation chain assembly Figure 20 Axonometric view of ball circulation chain 5 Figure 21 Front view of ball circulation chain 5 Figure 22 Side view of ball circulation chain 5 Figure 23 Axonometric view of ball circulation chain 6 Figure 24 Front view of ball circulation chain 6 Figure 25 Side view of ball circulation chain 6

[0014] Markings in the figure: 1 - ball screw, 11 - screw thread hole, 12 - return channel, 13 - screw spiral raceway, 14 - screw drive rod, 2 - ball nut, 21 - mating outer circle, 22 - nut spiral raceway, 3, 4 - returner, 31 - returner thread hole, 32 - ball retainer, 33 - through hole, 34 - ball inlet / outlet, 35 - ball outlet / inlet, 5, 6 - ball circulation chain, 51, 61 - straight section of circulation chain, 52, 62 - curved section of circulation chain. Detailed implementation mode

[0015] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Embodiment

[0016] As Figure 1 , Figure 2 , Figure 3 andFigure 4 As shown in the figure, the nut - reversed ball screw pair of this embodiment includes a ball nut 2 and a ball screw 1. The ball nut 2 is provided with a mating outer circle 21 for mating with the upper - level structure to receive the rotational motion of the upper - level structure. After the ball nut 2 is driven to rotate, it drives the ball screw 1 to perform an axial linear motion relative to the ball nut 2 through the ball circulation chain.

[0017] Combined with Figure 5 As shown in the figure, return devices 3 and 4 are respectively provided at both ends of the ball screw 1. There are two non - communicating ball circulation chains 5 and 6 between the ball nut 2, the ball screw 1, and the return devices 3 and 4.

[0018] Combined with Figure 6 、 Figure 7 、 Figure 8 and Figure 9 As shown in the figure, the ball screw pair of this embodiment is provided with no less than four even - numbered spiral raceways between the ball nut 2 and the ball screw 1, which can be four, six, eight, etc. In this embodiment, six is taken as an example for illustration, and the principle for the remaining number of raceways is the same.

[0019] The outer wall of the ball screw 1 is provided with six screw spiral raceways 13. The six screw spiral raceways 13 are evenly distributed on the outer wall surface of the ball screw 1 and are numbered ① - ⑥ in sequence. Then ①, ③, and ⑤ receive the driving force transmitted by the ball circulation chain 5, and ②, ④, and ⑥ receive the driving force transmitted by the ball circulation chain 6. The screw spiral raceway is the load - bearing part of the reverse - type ball screw. After bearing the load, it drives the entire reverse - type ball screw to perform a linear motion.

[0020] Correspondingly, as Figure 10 、 Figure 11 and Figure 12 shown in the figure, the inner wall of the ball nut 2 is also provided with six nut spiral raceways 22. Similarly, the six nut spiral raceways 22 are evenly distributed and are numbered ① - ⑥ in sequence. Then ①, ③, and ⑤ drive the ball circulation chain 5 to transmit the driving force to the reverse - type ball screw, and ②, ④, and ⑥ drive the ball circulation chain 6 to transmit the driving force to the reverse - type ball screw. After the ball nut 2 rotates itself, it drives the entire reverse - type ball screw to perform a linear motion.

[0021] The above - mentioned nut spiral raceways and screw spiral raceways are in one - to - one cooperation to form six spiral raceways.

[0022] The ball screw 1 is provided with six return channels 12 that penetrate axially. The six return channels 12 are evenly distributed circumferentially around the ball screw and are numbered ① - ⑥ in sequence. Then ①, ③, and ⑤ are used for the ball return of the ball circulation chain 5, and ②, ④, and ⑥ are used for the ball return of the ball circulation chain 6. The return channel 12 is a part of the space where the ball circulation chain is located.

[0023] The six spiral raceways and the return channels 12 correspond one by one and are respectively divided into two groups arranged at intervals, that is, ①, ③, and ⑤ are one group, and ②, ④, and ⑥ are the other group.

[0024] Combined Figure 13 , Figure 14 , Figure 15 and Figure 16 As shown in the figure, the returners 3 and 4 at both ends of the ball screw 1 have the same structure. Taking the returner 3 as an example, six return channels are provided in the returner 3, which are respectively connected to the corresponding spiral raceways and return channels; six ball inlets / outlets 34 that are respectively connected to the six spiral raceways are evenly arranged along the circumferential direction of the edge of the returner 3, for guiding the balls to enter and exit the internal space of the returner 3 from the spiral raceways, and they are numbered ① - ⑥ in sequence; then ①, ③, and ⑤ belong to the ball circulation chain 5, and ②, ④, and ⑥ belong to the ball circulation chain 6.

[0025] Six ball outlets / inlets 35 that are respectively connected to the six return channels 12 are evenly arranged along the circumferential direction of one side of the returner 3, for guiding the balls to enter and exit the internal space of the returner 3 from the return channels, and they are numbered ① - ⑥ in sequence; then ①, ③, and ⑤ belong to the ball circulation chain 5, and ②, ④, and ⑥ belong to the ball circulation chain 6.

[0026] The six ball inlets / outlets 34 and the six ball outlets / inlets 35 correspond one by one and are respectively connected through a return channel; the six spiral raceways and the return channels 12 are also respectively connected through a return channel. Then, the spiral raceways, return channels, and the corresponding return channels of ①, ③, and ⑤ form a circulation channel, and the ball circulation chain 5 is arranged in this circulation channel; the spiral raceways, return channels, and the corresponding return channels of ②, ④, and ⑥ form another circulation channel, and the ball circulation chain 6 is arranged in this circulation channel.

[0027] A ball stopper 32 is provided at each spiral raceway corresponding to the returner 3, for preventing the balls from deviating from the raceway and preventing external dust from entering the raceway.

[0028] A lead screw drive rod 14 is provided at one end of the shaft of the ball screw 1. The returner 3 at this end is sleeved on the lead screw drive rod 14. A through hole 33 for the lead screw drive rod 14 to pass through is provided at the center of the corresponding returner 3, and the diameter of the through hole matches the diameter of the lead screw drive rod 14, preventing external dust from entering the interior.

[0029] The lead screw drive rod 14 of the ball screw pair with the nut reversed in this embodiment is rotationally driven by the external ball nut 2. Only by attaching a permanent magnet to the outside of the ball nut 2, the ball nut can be used as a servo motor, achieving integration and miniaturization.

[0030] On one side of the return device 3, six return device threaded holes 31 are evenly arranged circumferentially. The six return device threaded holes 31 are arranged at intervals from the six ball inlets / outs 35. At both ends of the ball screw 1, screw threaded holes 11 corresponding to the return device threaded holes 31 are provided. The return device threaded holes 31 and the screw threaded holes 11 cooperate with screws to fix the return device 3 on the ball screw 1.

[0031] Combined Figure 17 、 Figure 18 、 Figure 19 、 Figure 20 、 Figure 21 、 Figure 22 、 Figure 23 、 Figure 24 and Figure 25 As shown, the ball circulating chains 5 and 6 are arranged at intervals and are not connected to each other. The number of balls and the spatial structure of the two ball circulating chains are exactly the same, but the positions are 60 degrees different relative to the axis, that is, the phase angle between them is 60 degrees. Each of the two ball circulating chains includes a circulating chain straight section 51, 61 and a circulating chain curved section 52, 62. The circulating chain straight section is formed by the balls wrapped by the space where the return channel 12 is located, and the circulating chain curved section is formed by the balls wrapped by the space where the spiral raceway and the return channel are located. Each ball circulating chain includes 3-start threads, which can effectively enhance the load-bearing capacity. The overall structure of the two ball circulating chains is evenly distributed in space, ensuring the balance during loading and making the transmission stable.

[0032] In this embodiment, the phase angle between the two sets of nut spiral raceways or screw spiral raceways can be set in the range of 59 to 61 degrees. When both are 60 degrees, that is, they match the two ball circulating chains and carry the load together; when one of the phase angles between the two sets of nut spiral raceways or screw spiral raceways is 60 degrees and the other is not 60 degrees, for example, the phase angle between the two sets of screw spiral raceways is 60 degrees, and the phase angles of the two sets of nut spiral raceways are 59 degrees or 61 degrees, such a misalignment relationship will be generated with the screw. After installation, a pre-tightening force will be formed between the screw and the nut.

[0033] The technical solutions of the present invention are not limited to the above embodiments. All technical solutions obtained by equivalent replacement fall within the scope of protection required by the present invention.

Claims

1. A nut-reversed ball screw pair, comprising a ball nut and a ball screw that moves axially relative to the ball nut, characterized in that: The inner wall of the ball nut is provided with an even number of nut spiral raceways of no less than four, and correspondingly, the outer wall of the ball screw is provided with the same number of screw spiral raceways, and the nut spiral raceways and the screw spiral raceways cooperate one-to-one to form a corresponding number of spiral raceways; a corresponding number of reflux channels are arranged axially through the ball screw, and the reflux channels are evenly distributed along the circumference of the ball screw; the corresponding number of spiral raceways and reflux channels correspond one-to-one and are respectively divided into two groups arranged at intervals; a returner is respectively provided at both ends of the ball screw, and a corresponding number of return channels respectively connected to the corresponding spiral raceways and reflux channels are provided in the returner; the spiral raceways, reflux channels and corresponding return channels of each group form a circulation channel, and the two circulation channels are not connected to each other and are respectively provided with a ball circulation chain.

2. The nut-inverted ball screw pair according to claim 1, characterized in that: There are six spiral raceways.

3. The nut-inverted ball screw pair according to claim 2, characterized in that: The edge of the returner is circumferentially provided with six ball inlets / outlets respectively connected to the six spiral raceways, and one side of the returner is circumferentially provided with six ball inlets / outlets respectively connected to the six reflux channels. The six ball inlets / outlets and the six ball inlets / outlets correspond one to one and are respectively connected through a return channel.

4. The nut-inverted ball screw pair according to claim 3, characterized in that: The returner is provided with a bead stopper corresponding to each spiral raceway.

5. The nut-inverted ball screw pair according to any one of claims 1 to 4, characterized in that: A screw transmission rod is provided at one end of the ball screw shaft, and a returner at this end is sleeved on the screw transmission rod. A through hole is provided at the center of the returner for the screw transmission rod to pass through.

6. The nut-inverted ball screw pair according to claim 5, characterized in that: One side surface of the returner is provided with six returner threaded holes along the circumferential direction, and the six returner threaded holes are arranged at intervals with the six ball inlets / outlets; both ends of the ball screw are provided with screw threaded holes corresponding to the returner threaded holes.

7. The nut-inverted ball screw pair according to claim 1, characterized in that: The phase angle between the two ball circulation chains is 60 degrees, and the phase angle between the two sets of nut spiral raceways and the two sets of lead screw spiral raceways is at least one of 60 degrees and the other is 59 to 61 degrees.

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