A forward type planetary roller screw applied to a robot

Abstract

The application provides a forward type planetary roller screw applied to a robot and relates to the roller screw technical field.The forward type planetary roller screw comprises an outer layer nut, a planetary follow-up nut is clamped in the inner part of the outer layer nut, the planetary follow-up nut comprises a plurality of planetary nuts, the plurality of planetary nuts are arranged along the length direction of the outer layer nut, the planetary follow-up nut is rotationally connected with a planetary roller assembly, and the planetary roller assembly is rotationally connected with a screw.The beneficial effect of the application is that the forward type planetary roller screw applied to the robot is provided, the combination of the plurality of planetary follow-up nuts and the outer layer nut is used to replace the design of the single nut, the length of the planetary follow-up nut can be greatly shortened, the difficulty of internal thread machining is reduced, the machining precision can be more easily controlled in the machining process, the error accumulation caused by the length is reduced, the machining difficulty is effectively reduced, the interference and vibration in the machining process are reduced, the machining stability is improved, and the machining cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of ball screw technology, and in particular to a forward planetary ball screw for use in robots. Background Technology

[0002] Forward planetary roller screws, used in robots, play a crucial role in modern industry as a precision mechanical transmission device. They enable efficient conversion between rotary and linear motion, and thanks to their unique structure and superior performance, they have become an ideal replacement for ball screws in high-load applications. The core working principle of forward planetary roller screws in robots stems from their ingenious planetary gear system design. During operation, the rollers, like planetary gears in a planetary gear system, exhibit a unique motion pattern. They not only rotate around their own axis but also revolve along the inner cavity of the nut. This composite motion makes forward planetary roller screws used in robots transmit power more smoothly and efficiently, and can withstand greater loads and impacts.

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

[0004] However, the manufacturing process of forward planetary roller screws used in robots faces numerous challenges. Among these, the machining of the internal thread is a major hurdle. The internal threads of forward planetary roller screws used in robots typically require considerable length because their precision directly affects the transmission accuracy, load capacity, and service life of the screw. To achieve high precision, advanced machining equipment and processes are required, such as high-precision thread grinders and CNC machining centers. Simultaneously, strict control of various parameters during machining, such as cutting speed, feed rate, and depth of cut, is necessary to ensure the dimensional accuracy and surface quality of the internal thread.

[0005] Currently, the traditional design of forward planetary roller screws used in robots connects to the rollers and screw by creating an internal thread on the inner circumference of the nut. However, this connection method also brings a series of problems. Because a fairly long and high-precision thread needs to be machined on the inner circumference of the nut, it places extremely high demands on the machining equipment and processes. On the one hand, the machining process requires a lot of time and effort, leading to low production efficiency; on the other hand, the high-precision machining requirements greatly increase the machining difficulty, making it prone to machining errors and thus reducing the yield of finished products. Furthermore, to ensure the accuracy of the internal thread, expensive machining equipment and testing instruments are required, which undoubtedly increases production costs. Summary of the Invention

[0006] This invention overcomes the shortcomings of existing technologies and provides a forward-moving planetary roller screw for robots. It replaces the single-nut design with a combination of several planetary follower nuts and an outer nut, significantly reducing the length of the planetary follower nuts. On one hand, this reduces the difficulty of internal thread machining, making it easier to control precision during processing and reducing the accumulation of errors caused by length. On the other hand, it effectively reduces machining difficulty, minimizes interference and vibration during machining, improves machining stability, and lowers machining costs.

[0007] To solve the above-mentioned technical problems, the invention is achieved through the following technical solution:

[0008] A forward-moving planetary roller screw for robots includes an outer nut, inside which a planetary follower nut is engaged. The planetary follower nut includes a plurality of planetary nuts arranged along the length of the outer nut. The planetary follower nut is rotatably connected to a planetary roller assembly, and the planetary roller assembly is rotatably connected to the screw.

[0009] Furthermore, the inner side of the outer nut is provided with an axial inner groove, and the outer wall of the planetary follower nut is provided with an outer groove;

[0010] The fit between the outer bolt groove and the axial inner bolt groove restricts the circumferential rotation of the planetary follower nut relative to the outer nut.

[0011] Furthermore, the outer nut is threadedly connected to a set screw, the end of which presses against the planetary nut to fix its axial position relative to the outer nut.

[0012] Furthermore, the planetary roller assembly includes a planetary carrier with several rollers connected in a ring on the planetary carrier. The rollers are rotatably connected to the planetary follower nut and the lead screw.

[0013] Furthermore, the roller has a threaded section in the middle and gear sections at both ends.

[0014] Furthermore, the rollers and planetary nuts must rotate in the same direction;

[0015] The lead screw only rotates and does not move axially; the planetary nut and outer nut only move axially and do not rotate; the rollers rotate and move axially, and the axial movements of the rollers, planetary nuts, and outer nuts must be synchronized; at this time, the ratio of the number of teeth of the planetary nut to the number of teeth of the rollers must be equal to the ratio of their thread pitch circle diameters, and the number of teeth of the lead screw must be equal to the number of teeth of the planetary nut.

[0016] Furthermore, the planetary follower nut has several planetary nuts in the middle and ring gears and hole retaining rings at both ends;

[0017] The axial relative position of the planetary roller assembly to the outer nut is restricted between two hole retaining rings.

[0018] Furthermore, the threaded section of the roller is connected to the inner thread of the planetary nut, and the gear section of the roller meshes with the ring gear.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] By replacing the single-nut design with a combination of several planetary follower nuts and an outer nut, the length of the planetary follower nuts can be significantly shortened, making it easier to control precision during machining and reducing the accumulation of errors caused by length. On the other hand, the machining difficulty is also effectively reduced, interference and vibration during machining are decreased, machining stability is improved, and machining costs are lowered. Attached Figure Description

[0021] The accompanying drawings are provided to further illustrate the invention and, together with the embodiments thereof, are used to explain the invention. They do not constitute a limitation thereof. In the drawings:

[0022] Figure 1This is a schematic diagram of the overall shape of the forward planetary roller screw applied to a robot according to an embodiment of the present invention;

[0023] Figure 2 This is a cross-sectional view of a forward planetary roller screw applied to a robot according to an embodiment of the present invention;

[0024] Figure 3 This is an exploded view of a forward planetary roller screw applied to a robot according to an embodiment of the present invention.

[0025] Figure 4 This is an exploded schematic diagram of a planetary roller assembly according to an embodiment of the present invention.

[0026] In the diagram: 1. Outer nut; 101. Axial inner groove; 2. Planetary follower nut; 201. Ring gear; 202. Planetary nut; 2021. Outer groove; 2022. Set screw; 203. Hole retainer; 3. Planetary roller assembly; 301. Roller; 3011. Thread section; 3012. Gear section; 302. Planetary carrier; 4. Lead screw. Detailed Implementation

[0027] The preferred embodiments of the invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the invention.

[0028] like Figures 1 to 4 As shown, a forward planetary roller screw for robots includes an outer nut 1, inside which a planetary follower nut 2 is snapped. The planetary follower nut 2 includes several planetary nuts 202, which are arranged along the length of the outer nut 1. This arrangement enables the mechanism to transmit power and achieve motion conversion more stably during operation.

[0029] The planetary follower 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. The inner side of the outer nut 1 is provided with an axial inner groove 101, and the outer wall of the planetary follower nut 2 is provided with an outer groove 2021. The cooperation between the outer groove 2021 and the axial inner groove 101 restricts 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 groove 2021 and the axial inner groove 101 cooperate with each other, effectively restricting the circumferential rotation of the planetary follower nut 2 relative to the outer nut 1, thus ensuring the stability and accuracy of the mechanism during operation.

[0030] In a forward planetary roller screw used in a robot, a number of planetary nuts 202 are provided in the middle of the planetary follower nut 2, and ring gears 201 are provided at both ends; 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.

[0031] In a forward-rotating planetary roller screw used in robots, the rollers 301 and planetary nuts 202 must have the same direction of rotation. The screw 4 only rotates and does not move axially. The planetary nuts 202 and outer nuts 1 only move axially and do not rotate. The rollers 301 rotate and move axially, and their axial movements must be synchronized with those of the planetary nuts 202 and outer nuts 1. The ratio of the number of teeth in the planetary nuts 202 to the number of teeth in the rollers 301 must be equal to the ratio of their thread pitch circle diameters; otherwise, the planetary nuts 202 and rollers 301 cannot move axially synchronously. The number of teeth in the screw 4 must be equal to the number of teeth in the planetary nuts 202; otherwise, the displacement speed of the planetary nuts 202 and the rotational speed of the screw 4 will not be linearly related.

[0032] The planetary roller assembly 3 consists of a planetary carrier 302 and several rollers 301, which are connected to the planetary carrier 302 in a ring shape. The rollers 301 have a threaded section 3011 in the middle and gear sections 3012 at both ends. The planetary follower nut 2 has several planetary nuts 202 in the middle and ring gears 201 and retaining rings 203 at both ends. The axial relative position of the planetary roller assembly 3 to the outer nut 1 is restricted between two retaining rings 203. The threaded section 3011 connects to the threads on the inner side of the planetary nut 202, and the gear sections 3012 mesh with the ring gears 201 of the planetary follower nut 2. This structural design enables the rollers 301 to achieve efficient power transmission and motion conversion between the planetary follower nut 2 and the lead screw 4.

[0033] The mechanism employs a design with multiple planetary follower nuts 2 and rollers 301, which allows the load to be evenly distributed across the components. Compared to traditional lead screw mechanisms, its load-bearing capacity is significantly improved, meeting the requirements of high-load conditions and making it suitable for transmission systems of heavy machinery.

[0034] Traditional mechanisms typically employ a single threaded nut, also referred to as a nut in this paper, though the terminology differs; both refer to the same structural product. This mechanism replaces this single-nut design with a combination of several planetary follower nuts 2 and an outer nut 1. This innovative design offers numerous advantages, the most significant being a substantial reduction in the length of the planetary follower nuts 2, which can be reduced to less than half the length of a typical nut.

[0035] The reduction in length is significant for machining the internal threads of the planetary follower nut 2. On one hand, it reduces the difficulty of machining the internal threads. In traditional machining of long nuts, ensuring the accuracy of the entire thread is challenging due to its length. However, the shorter planetary follower nut 2 in this mechanism makes it easier to control accuracy during machining, reducing the accumulation of errors caused by length. On the other hand, the machining difficulty is also effectively reduced. The shorter length allows for greater flexibility in tool operation, reducing interference and vibration during machining and improving machining stability.

[0036] In summary, this design significantly improves the internal thread machining speed of the planetary follower nut 2, thereby increasing the overall production efficiency of the mechanism, reducing production costs, and providing strong support for the widespread application of this mechanism in the industrial field.

[0037] Finally, it should be noted that the above are merely 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 foregoing embodiments or make equivalent substitutions for some of the technical features. However, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A forward-rotating planetary roller screw for robots, characterized in that, It includes an outer nut (1), and a planetary follower nut (2) is snapped into the inner part of the outer nut (1). The planetary follower nut (2) includes several planetary nuts (202), which are arranged along the length direction of the outer nut (1). The planetary follower 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). The outer nut (1) has an axial inner groove (101) on its inner side, and the planetary follower nut (2) has an outer groove (2021) on its outer wall. The engagement of the outer bolt groove (2021) and the inner bolt groove (101) restricts the circumferential rotation of the planetary follower nut (2) relative to the outer nut (1); The planetary roller assembly (3) includes a planetary carrier (302), on which a plurality of rollers (301) are connected in a ring. The rollers (301) are rotatably connected to the planetary follower nut (2) and the lead screw (4). The roller (301) has a threaded section (3011) in the middle and gear sections (3012) at both ends. The planetary follower nut (2) is provided with ring gears (201) and hole buckles (203) at both ends; The axial relative position of the planetary roller assembly (3) to the outer nut (1) is restricted between the two hole retainers (203); The gear segment (3012) of the roller (301) meshes with the ring gear (201); The threaded section (3011) of the roller (301) is threaded to the inner side of the planetary nut (202) and threaded to the lead screw (4).

2. The forward planetary roller screw for robots according to claim 1, characterized in that, The outer nut (1) is threaded with a set screw (2022), the end of which presses against the planetary nut (202) to fix its axial position relative to the outer nut (1).

3. The forward planetary roller screw for robots according to claim 2, characterized in that, The rollers (301) and planetary nuts (202) must have the same rotation direction; The lead screw (4) only rotates and does not move axially. The planetary nut (202) and the outer nut (1) only move axially and do not rotate. The roller (301) rotates and moves axially, and the axial movement of the roller (301) must be synchronized with that of the planetary nut (202) and the outer nut (1). 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 circle diameters, and the number of teeth of the lead screw (4) must be equal to the number of teeth of the planetary nut (202).

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