Forward planetary roller screw applied to robot

Abstract

The invention provides a forward planetary roller lead screw applied to a robot, and relates to the technical field of roller lead screws, the forward planetary roller lead screw comprises an outer-layer nut, a planetary accompanying nut is clamped in the outer-layer nut, the planetary accompanying nut comprises a plurality of planetary nuts, the planetary nuts are arranged in the length direction of the outer-layer nut, and the outer-layer nut is connected with the outer-layer nut. The planetary accompanying nut is rotationally connected with the planetary roller assembly, and the planetary roller assembly is rotationally connected with the lead screw. The forward planetary roller screw applied to the robot has the beneficial effects that the forward planetary roller screw applied to the robot is provided, the design of a single nut is replaced with the combination of the multiple planetary accompanying nuts and the outer-layer nut, the length of the planetary accompanying nuts can be greatly shortened, the difficulty of internal thread machining is reduced, and the machining efficiency is improved. The precision can be controlled more easily in the machining process, and error accumulation caused by the length is reduced; and the machining difficulty is effectively reduced, interference and vibration in the machining process are reduced, the machining stability is improved, and the machining cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of roller screws, and in particular to a forward planetary roller screw used in robots. Background Art

[0002] As a precision mechanical transmission device, the positive planetary roller screw used in robotics plays a vital role in modern industry. It enables efficient conversion between rotational and linear motion. Its unique structure and superior performance make it an ideal alternative to ball screws in high-load applications. The core operating principle of the positive planetary roller screw used in robotics stems from its ingenious planetary gear system design. During operation, the rollers, like the planetary gears in a planetary gear system, exhibit a unique motion. They not only rotate about their own axes but also orbit around the inner cavity of the nut. This compound motion enables the positive planetary roller screw used in robotics to transmit power more smoothly and efficiently, allowing it to withstand greater loads and impact forces.

[0003] Positive planetary roller screws for robotics are primarily used in the robotics field. In heavy-duty industrial robots, such as welding robots and handling robots, these positive planetary roller screws provide strong thrust and rigidity in the arm and forearm joints, where loads are high. Their compact design and low inertia offer significant advantages for end-of-arm tools, such as grippers and machining tools, that require high thrust within confined spaces. Their micron-level displacement control ensures precise grasping or machining movements while minimizing the impact of end-load loads on the robot's dynamic response. In applications such as logistics handling and heavy assembly, positive planetary roller screws can be used to drive the robot's lifting platform or walking mechanism. Their impact resistance and long lifespan allow them to adapt to high-load motion requirements in complex working conditions, improving the stability and reliability of the equipment. In specialized equipment such as powered exoskeletons and disaster relief robots, these positive planetary roller screws, through their high force-to-weight ratio, provide human assistance or load-bearing capabilities while maintaining lightweight design. For example, the hip and knee joint drives of the exoskeleton can rely on it to achieve large torque output and precise gait control. Compared with traditional ball screws, the line contact design of the positive planetary roller screw used in robots greatly improves its load-bearing capacity, axial stiffness and life, and is especially suitable for the long-term stable operation of robots under high load and high-frequency motion.

[0004] However, the positive planetary roller screws used in robots face many challenges in the processing and manufacturing process. Among them, the processing of internal threads is a key problem. The internal threads of positive planetary roller screws used in robots are usually required to be quite long. This is because the accuracy of the internal threads directly affects the transmission accuracy, load capacity and service life of the positive planetary roller screws used in robots. In order to achieve high-precision requirements, the processing process requires the use of advanced processing equipment and processes, such as high-precision thread grinders, CNC machining centers, etc. At the same time, it is also necessary to strictly control various parameters in the processing process, such as cutting speed, feed rate, cutting depth, etc., to ensure the dimensional accuracy and surface quality of the internal threads.

[0005] The traditional design of the forward planetary roller screw currently used in robots on the market is to achieve connection with the roller and screw by providing an internal thread on the inner circumference of the nut. However, this connection method also brings a series of problems. Since it is necessary to process a relatively long and high-precision thread on the inner circumference of the nut, this places extremely high demands on the processing equipment and process. On the one hand, the processing requires a lot of time and energy, resulting in low production efficiency; on the other hand, the high-precision processing requirements make the processing difficulty greatly increased, and processing errors are prone to occur, thereby reducing the yield of the finished product. In addition, in order to ensure the accuracy of the internal thread, expensive processing equipment and testing instruments are also required, which undoubtedly increases production costs. Summary of the Invention

[0006] The invention overcomes the shortcomings of the prior art and provides a forward-acting planetary roller screw for robotic applications. This design replaces the single nut design with a combination of several planetary follower nuts and an outer nut, significantly shortening the length of the planetary follower nut. This reduces the difficulty of machining the internal thread, facilitating precision control during machining and minimizing the cumulative error caused by length. Furthermore, the manufacturing difficulty is significantly reduced, interference and vibration are minimized, processing stability is improved, and costs are lowered.

[0007] In order to solve the above technical problems, the invention is achieved through the following technical solutions: A forward planetary roller screw for use in robots includes an outer nut with a planetary follower nut clamped inside the outer nut. The planetary follower nut includes several planetary nuts, which are arranged along the length direction of the outer nut. The planetary follower nuts are rotatably connected to the planetary roller assembly, and the planetary roller assembly is rotatably connected to the screw.

[0008] Furthermore, an axial inner fastening groove is provided on the inner side of the outer nut, and an outer fastening groove is provided on the outer wall of the planetary accompanying nut; The cooperation between the outer tethering groove and the axial inner tethering groove limits the circumferential rotation of the planetary follower nut relative to the outer nut.

[0009] Furthermore, the outer nut is threadedly connected to a set screw, and the end of the set screw presses against the planetary nut to fix its axial position relative to the outer nut.

[0010] Furthermore, the planetary roller assembly includes a planetary carrier, on which a plurality of rollers are connected in a ring shape, and the rollers are rotationally connected to the planetary follower nut and the lead screw at the same time.

[0011] Furthermore, the middle of the roller is a screw thread section, and both ends are gear sections.

[0012] Furthermore, the rotation directions of the roller and the planetary nut must be the same; The lead screw only performs rotational motion and does not move axially. The planetary nut and the outer nut only perform axial motion and do not perform rotational motion. The roller performs both rotational motion and axial motion, and the axial motion of the roller, the planetary nut and the outer nut must be synchronized. At this time, the ratio of the number of teeth of the planetary nut to the number of teeth of the roller must be equal to the ratio of their thread pitch diameters, and the number of teeth of the lead screw must be equal to the number of teeth of the planetary nut.

[0013] Furthermore, a plurality of planetary nuts are arranged in the middle of the planetary accompanying nut, and ring gears and retaining rings for holes are arranged at both ends; The axial relative position of the planetary roller assembly relative to the outer nut is restricted between two hole retaining rings.

[0014] Furthermore, the thread segment of the roller is connected to the thread inside the planetary nut, and the gear segment of the roller is meshed and connected to the ring gear.

[0015] Compared with the prior art, the present invention has the following beneficial effects: By replacing the single nut design with a combination of several planetary traveler nuts and an outer nut, the length of the planetary traveler nut can be significantly shortened, making it easier to control precision during machining and reducing the cumulative error caused by length. Furthermore, the machining difficulty is effectively reduced, interference and vibration are minimized, processing stability is improved, and costs are reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are used to provide a further understanding of the invention and, together with the embodiments of the invention, to explain the invention, but do not constitute a limitation of the invention. In the accompanying drawings: Fig. 1 1 is a schematic diagram of the overall appearance of a forward-type planetary roller screw applied to a robot according to an embodiment of the present invention; Fig. 2is a cross-sectional view of a forward-type planetary roller screw applied to a robot according to an embodiment of the present invention; Fig. 3 1 is an exploded schematic diagram of a forward-type planetary roller screw applied to a robot according to an embodiment of the present invention; Fig. 4 2. It is an exploded schematic diagram of a planetary roller assembly according to an embodiment of the present invention.

[0017] In the figure: 1. Outer nut; 101. Axial inner bolting groove; 2. Planetary trailing nut; 201. Ring gear; 202. Planetary nut; 2021. Outer bolting groove; 2022. Set screw; 203. Hole retaining ring; 3. Planetary roller assembly; 301. Roller; 3011. Thread segment; 3012. Gear segment; 302. Planet carrier; 4. Screw. DETAILED DESCRIPTION

[0018] The preferred embodiments of the invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the invention and are not used to limit the invention.

[0019] like Figs. 1 to 4 As shown, a forward planetary roller screw used in a robot includes an outer nut 1, a planetary follower nut 2 is clamped inside the outer nut 1, and the planetary follower nut 2 includes a plurality of planetary nuts 202. The plurality of planetary nuts 202 are arranged along the length direction of the outer nut 1. This arrangement enables the mechanism to transmit power and realize motion conversion more stably during operation.

[0020] The planetary follower nut 2 is rotationally connected to the planetary roller assembly 3, and the planetary roller assembly 3 is rotationally connected to the screw 4. An axial inner tether groove 101 is provided on the inner side of the outer nut 1, and an outer tether groove 2021 is provided on the outer wall of the planetary follower nut 2; the cooperation between the outer tether groove 2021 and the axial inner tether groove 101 limits the circumferential rotation of the planetary follower nut 2 relative to the outer nut 1. When the planetary follower nut 2 is installed inside the outer nut 1, the outer tether groove 2021 and the axial inner tether groove 101 cooperate with each other, effectively limiting the circumferential rotation of the planetary follower nut 2 relative to the outer nut 1, thereby ensuring the stability and accuracy of the mechanism during operation.

[0021] In the forward planetary roller screw used in robots, several planetary nuts 202 are arranged in the middle of the planetary follower nut 2, and ring gears 201 are set at both ends; the outer nut 1 is threadedly connected with a set screw 2022, and the end of the set screw 2022 presses the planetary nut 202 to fix its axial position relative to the outer nut 1.

[0022] In the forward planetary roller screw used in robots, the rotation direction of the roller 301 and the planetary nut 202 must be the same, the screw 4 only performs rotational motion, and does not perform axial movement; the planetary nut 202 and the outer nut 1 only perform axial movement, and do not perform rotational motion; the roller 301 performs both rotational motion and axial movement, and the axial movement of the roller 301 and the planetary nut 202 and the outer nut 1 must be synchronized, wherein the ratio of the number of teeth of the planetary nut 202 to the number of teeth of the roller 301 must be equal to the ratio of their thread pitch diameters, otherwise the planetary nut 202 and the roller 301 cannot be synchronously displaced axially, and the number of teeth of the screw 4 must be equal to the number of teeth of the planetary nut 202, otherwise the displacement speed of the planetary nut 202 will not be linearly related to the rotation speed of the screw 4.

[0023] The planetary roller assembly 3 consists of a planetary carrier 302 and several rollers 301, which are annularly connected to the planetary carrier 302. The rollers 301 have a screw segment 3011 in the middle and gear segments 3012 at both ends. Several planetary nuts 202 are arranged in the middle of the planetary traveler nut 2, with ring gears 201 and hole retaining rings 203 at both ends. The axial relative position of the planetary roller assembly 3 relative to the outer nut 1 is restricted between the two hole retaining rings 203. The screw segment 3011 is connected to the inner thread of the planetary nut 202, and the gear segment 3012 meshes with the ring gear 201 of the planetary traveler nut 2. This structural design enables the rollers 301 to achieve efficient power transmission and motion conversion between the planetary traveler nut 2 and the lead screw 4.

[0024] The mechanism adopts a design of multiple planetary tracking nuts 2 and rollers 301, so that the load can be evenly distributed on each component. Compared with the traditional screw mechanism, its load-bearing capacity has been significantly improved, which can meet the use requirements under high-load conditions and is suitable for the transmission system of heavy machinery and equipment.

[0025] Traditional mechanisms typically use a single internally threaded nut. In the art, this nut is also referred to as a nut. While the two terms differ, they refer to the same structural product. This mechanism replaces this single nut design with a combination of several planetary accompanying nuts 2 and an outer nut 1. This innovative design offers numerous benefits, the most notable of which is that the length of the planetary accompanying nuts 2 can be significantly shortened, to less than half the length of a typical nut.

[0026] The shortened length is of great significance for the internal thread processing of the planetary follower nut 2. On the one hand, it reduces the difficulty of internal thread processing. In the traditional long nut internal thread processing, due to the long length, it is difficult to ensure the accuracy of the entire thread. The shorter planetary follower nut 2 in this mechanism makes it easier to control the accuracy during the processing process and reduces the error accumulation caused by length. On the other hand, the processing difficulty is also effectively reduced. The shorter length makes the processing tool more flexible during operation, reduces interference and vibration during the processing, and improves the stability of the processing.

[0027] In summary, this design enables the internal thread processing speed of the planetary follower nut 2 to be significantly improved, thereby improving the production efficiency of the entire mechanism, reducing production costs, and providing strong support for the wide application of the mechanism in the industrial field.

[0028] Finally, it should be noted that the above are only preferred embodiments of the invention and are not intended to limit the invention. Although the invention has been described in detail with reference to the embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. However, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the invention should be included in the scope of protection of the invention.

Claims

1. A positive planetary roller screw for a robot, characterized in that: The outer nut (1) includes a planetary accompanying nut (2) clamped inside the outer nut (1), the planetary accompanying nut (2) includes a plurality of planetary nuts (202), the plurality of planetary nuts (202) are arranged along the length direction of the outer nut (1), the planetary accompanying nut (2) is rotatably connected to the planetary roller assembly (3), and the planetary roller assembly (3) is rotatably connected to the lead screw (4).

2. The positive planetary roller screw for robots according to claim 1, characterized in that: The inner side of the outer nut (1) is provided with an axial inner fastening groove (101), and the outer wall of the planetary accompanying nut (2) is provided with an outer fastening groove (221); The cooperation between the outer tether groove (2021) and the axial inner tether groove (101) limits the circumferential rotation of the planetary follower nut (2) relative to the outer nut (1).

3. The positive planetary roller screw for robots according to claim 2, characterized in that: The outer nut (1) is threadedly connected to a set screw (2022), and the end of the set screw (2022) presses against the planetary nut (202) to fix its axial position relative to the outer nut (1).

4. The positive planetary roller screw for a robot according to any one of claims 1 to 3, characterized in that: The planetary roller assembly (3) comprises a planetary frame (302), a plurality of rollers (301) are connected to the planetary frame (302) in a ring shape, and the rollers (301) are rotationally connected to the planetary accompanying nut (2) and the lead screw (4).

5. The positive planetary roller screw for robots according to claim 4, characterized in that: The middle of the roller (301) is a screw thread section (3011), and both ends are gear sections (3012).

6. The positive planetary roller screw for robots according to claim 5, characterized in that: The directions of rotation of the roller (301) and the planetary nut (202) must be the same; The lead screw (4) only performs rotational motion and does not perform axial movement, and the planetary nut (202) and the outer nut (1) only perform axial movement and do not perform rotational motion; the roller (301) performs both rotational motion and axial movement, and the axial movement of the roller (301) and the planetary nut (202) and the outer nut (1) must be synchronized; at this time, the ratio of the number of teeth of the planetary nut (202) to the number of teeth of the roller (301) must be equal to the ratio of their thread pitch diameters, and the number of teeth of the lead screw (4) must be equal to the number of teeth of the planetary nut (202).

7. The positive planetary roller screw for robots according to claim 6, characterized in that: A plurality of planetary nuts (202) are provided in the middle of the planetary accompanying nut (2), and ring gears (201) and hole retaining rings (203) are provided at both ends; The axial relative position of the planetary roller assembly (3) relative to the outer nut (1) is restricted between two hole retaining rings (203).

8. The positive planetary roller screw for robots according to claim 6, characterized in that: The threaded section (3011) of the roller (301) is connected to the inner thread of the planetary nut (202) and is also connected to the lead screw (4). The gear section (3012) of the roller (301) is meshed with the ring gear (201).

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