Planetary roller screw drive assembly

Abstract

The utility model provides a planetary roller screw transmission assembly. The planetary roller screw transmission assembly comprises a nut, a screw, a plurality of rollers, a retainer group and a friction elastic piece, the nut is provided with an axially penetrating inner hole, and the inner circumferential surface of the nut is provided with at least one annular groove section and at least one non-tooth-shaped section adjacent to the annular groove section. The screw rod is arranged in the inner hole in a penetrating mode and extends out of the nut. A plurality of rollers are arranged in an inner hole of the nut and arranged on the periphery of the screw in a surrounding mode, each roller is provided with at least one large-pitch-diameter section and at least one small-pitch-diameter section with a smooth face in the axial direction, the large-pitch-diameter sections are provided with annular teeth used for being meshed with the screw in a rolling mode, and the small-pitch-diameter sections are provided with annular teeth used for being meshed with the nut in a rolling mode. The retainer group is arranged at the axial end parts of the plurality of rollers. The friction elastic piece is arranged on the non-tooth-shaped section of the inner circumferential face of the nut and makes interference contact with the smooth face of the small-pitch-diameter section of the multiple pin rollers.

Description

Technical Field

[0001] This utility model relates to a transmission component, and more particularly to a planetary roller screw transmission component that can provide radial preload to the rollers to improve rolling engagement stability. Background Technology

[0002] Planetary roller screw drives, characterized by high load-bearing capacity, high rigidity, excellent transmission efficiency, and positioning accuracy, are widely used in precision machine tools, servo drive systems, aerospace control devices, robotics, and other fields demanding rapid response and high dynamic performance. This assembly utilizes multiple rollers positioned within a nut and surrounding the screw. Through the rolling engagement between the rollers, screw, and nut, the screw's rotational motion is converted into linear motion relative to the nut, thereby driving external loads.

[0003] Please see Figure 1A and Figure 1B As shown, a planetary roller screw drive device includes a screw 11, a nut 12, a plurality of rollers 13, and a retainer assembly 14. The screw 11 has a threaded structure, and the nut 12 has an inner hole 120 for accommodating the plurality of rollers 13, and internal teeth 12t are provided on the inner circumference of the nut 12 for meshing with the external teeth of the rollers 13 to form rolling contact. The retainer assembly 14 is disposed at both axial ends of the plurality of rollers 13 to position the plurality of rollers 13 between the screw 11 and the nut 12 and to maintain the circumferential spacing of the plurality of rollers 13.

[0004] Although the aforementioned retainer assembly 14 can provide the spacing and positioning functions of the rollers 13, it does not have a structural design that can provide friction or apply radial positive force to the rollers 13, nor can it effectively compensate for the radial engagement offset between the rollers 13 and the nut 12 and screw 11 caused by manufacturing tolerances and assembly errors.

[0005] like Figure 1A and Figure 1B As shown, the rolling meshing relationship between roller 13 and nut 12 mainly relies on the geometric fit of their tooth structures and the stable maintenance of the meshing contact position on their designed pitch circle. However, in practical applications, factors such as manufacturing tolerances, assembly errors, or changes in motion load can cause the contact position to deviate from its original ideal pitch circle, which can easily lead to unstable rolling contact and problems such as slippage and freewheeling. This situation will disrupt the pure rolling motion trajectory that roller 13 should have, thus hindering the maintenance of transmission efficiency.

[0006] On the other hand, the rolling contact between the rollers 13 and the screw 11 also faces similar problems. Since the retaining assembly 14 only provides the basic circumferential spacing and axial positioning of the plurality of rollers 13, and is not designed with a mechanism to apply radial preload to the contact area between the rollers 13 and the threaded structure of the screw 11, when the screw 11 is operating at high speed or under varying loads, the rollers 13 may experience radial displacement at the contact interface, causing the contact position to deviate from its designed pitch circle. Such displacement will make the rolling contact unstable, further leading to phenomena such as slippage or freewheeling, ultimately reducing the synchronicity and transmission stability of the planetary motion.

[0007] Therefore, how to improve the contact stability between the roller and the nut, enhance the rolling meshing effect between the roller and the screw, and effectively suppress slippage and freewheeling without significantly increasing component complexity and cost, thereby ensuring the stability of the overall planetary rolling motion, is a technical problem that urgently needs to be solved in this field. Utility Model Content

[0008] To address the aforementioned problems, the purpose of this invention is to provide a planetary roller screw transmission assembly.

[0009] This utility model provides a planetary roller screw transmission assembly, characterized in that it includes:

[0010] A nut having an axially penetrating inner hole, the inner circumferential surface of the nut having at least one annular groove section and at least one non-toothed section adjacent to the annular groove section;

[0011] A screw rod passes through the inner hole of the nut and extends to the outside of the nut; the outer circumferential surface of the screw rod is provided with a threaded structure.

[0012] A plurality of rollers are disposed in the inner hole of the nut and arranged on the outer periphery of the screw. Each roller has a plurality of annular teeth on its outer peripheral surface, and each roller has at least one large pitch diameter section and at least one small pitch diameter section with a smooth surface along the axial direction. The large pitch diameter section has annular teeth for rolling engagement with the screw, and the small pitch diameter section has annular teeth for rolling engagement with the nut.

[0013] A retaining element assembly, disposed at the axial end of the plurality of rollers, for maintaining the circumferential spacing of the plurality of rollers; and

[0014] At least one friction elastic element is disposed in the non-toothed section of the inner circumferential surface of the nut and forms interference contact with the smooth surface of the small pitch diameter section of the plurality of rollers.

[0015] The planetary roller screw drive assembly further includes at least one relief groove section on the inner circumferential surface of the nut, which is located at the position corresponding to the large pitch diameter section of the plurality of rollers.

[0016] In the planetary roller screw drive assembly, the inner circumferential surface of the nut is provided with a first groove in the non-tooth section, and the friction elastic element is embedded in the first groove.

[0017] In the planetary roller screw drive assembly, the radial distance from the contact point where the friction elastic element and the smooth surface of the small pitch diameter section of the roller form interference contact to the geometric center of the nut is equal to the radial distance from the contact point where the annular groove section of the nut and the small pitch diameter section of the roller form rolling contact to the geometric center of the nut.

[0018] The planetary roller screw drive assembly includes a screw with a pitch radius Rs, which is the radial distance from the point where the screw's thread structure and the large pitch diameter section of the roller form rolling contact to the geometric center of the screw; the large pitch diameter section of the roller has a pitch radius Rps, which is the radial distance from the point where the annular teeth of the large pitch diameter section and the screw's thread structure form rolling contact to the geometric center of the roller; the small pitch diameter section of the roller has a pitch radius Rpr, which is the radial distance from the point where the annular teeth of the small pitch diameter section and the annular groove section of the nut form rolling contact to the geometric center of the roller; and the nut has a pitch radius Rr, which is the radial distance from the point where the annular groove section of the nut and the small pitch diameter section of the roller form rolling contact to the geometric center of the nut. The pitch radii satisfy the following relationship: Rr = Rs + Rpr + Rps.

[0019] The planetary roller screw drive assembly includes a retainer group comprising two annular members sleeved on the screw and respectively disposed at the two axial ends of the plurality of rollers to jointly maintain the circumferential spacing of the plurality of rollers.

[0020] The planetary roller screw drive assembly wherein the annular member is provided with a plurality of positioning grooves, each positioning groove being used to accommodate the axial end of a corresponding roller to maintain the circumferential spacing of the plurality of rollers.

[0021] The planetary roller screw drive assembly further includes at least one fixing member disposed in the inner hole of the nut and abutting against the side of the annular member away from the plurality of rollers, so as to limit the axial displacement of the retaining member assembly within the nut.

[0022] Through this interference contact, radial preload can be applied to the multiple rollers, thereby achieving the following two technical effects: First, the radial preload generates static friction in the tangential component of the contact surface between the friction elastic element and the roller. This static friction can be used to stabilize the circumferential revolution of the roller, guiding it to move along the designed pitch circle trajectory, thus effectively preventing the roller from slipping or spinning relative to the nut; Second, the radial preload will also generate a positive force through the geometric contact structure of the roller, further enhancing the contact pressure and meshing force between the roller and the screw, enabling the roller, screw, and nut to maintain stable rolling contact, thereby improving the overall transmission efficiency. Attached Figure Description

[0023] Figure 1A This is a schematic diagram of an existing planetary roller screw drive.

[0024] Figure 1B for Figure 1A A schematic diagram of the meshing contact relationship between the roller and the nut.

[0025] Figure 2 This is an exploded view of the main components of the planetary roller screw transmission assembly according to the first embodiment of this utility model.

[0026] Figure 3A This is a cross-sectional schematic diagram of the planetary roller screw transmission assembly according to the first embodiment of this utility model.

[0027] Figure 3B This is an enlarged schematic diagram showing the tooth profile fit between the roller and the nut in the first embodiment of this utility model.

[0028] Figure 3C This is a cross-sectional schematic diagram of the planetary roller screw transmission assembly according to the second embodiment of this utility model.

[0029] Figure 4 This is a schematic diagram of the structure and configuration of the positioning component in the first embodiment of the present invention.

[0030] Figure 5 This is a schematic diagram of applying radial preload to the roller using a friction elastic element in the first embodiment of this utility model.

[0031] Figure 6A This is a schematic diagram showing the positioning of the roller at the pitch circle position after interference from the friction elastic element of the planetary roller screw transmission assembly in the first embodiment of this utility model.

[0032] Figure 6B For the corresponding Figure 6A A schematic diagram showing the relationship between the pitch circle configuration and planetary motion of a planetary roller screw drive assembly.

[0033] Explanation of reference numerals in the attached drawings: Planetary roller screw drive assembly 1; Nuts 10, 12; Internal teeth 12t; Inner holes 100, 120; Flange 101; Annular groove section 102; Annular teeth 102t; Annular groove 102g; Non-tooth section 103; First groove 104; Relief groove section 105; Second groove 106; Screws 11, 20; Threaded structure 201; Rollers 13, 30; Annular teeth 30t; Annular groove 30g; Large pitch diameter section 301; Small pitch diameter section 302; Smooth surface 302S; Friction elastic element 40; Retaining element assembly 14, 50; Ring member 50 r; Through hole 500; Protrusion structure 501; Positioning groove 502; Fixing element 60; Interference contact position between friction elastic element and roller P1; Position where nut and roller form rolling contact P2; Radial distance D1 from the interference contact position between friction elastic element and roller to the geometric center of nut; Radial distance D2 from the position where nut and roller form rolling contact to the geometric center of nut; Pitch circle radius Rs of screw; Pitch circle radius Rps of the large pitch diameter section of roller; Pitch circle radius Rpr of the small pitch diameter section of roller; Pitch circle radius Rr of nut; Radial preload F; Static friction force F1; Normal force F2. Detailed Implementation

[0034] The structural and functional characteristics of the planetary roller screw transmission assembly provided by this utility model will be described with reference to the preferred embodiment shown in the accompanying drawings.

[0035] Please see Figure 2 , Figure 3A and Figure 3B As shown.

[0036] The first embodiment of this utility model provides a planetary roller screw transmission assembly 1, including: a nut 10, a screw 20, a plurality of rollers 30, a retainer group 50, at least one fixing member 60, and at least one friction elastic member 40.

[0037] The nut 10 is a hollow cylindrical component with an inner hole 100 extending through both ends along its axial direction. One end may have a radially outwardly expanding flange 101, which serves as a positioning reference or stop structure for the nut 10 during assembly and allows the nut 10 to be fixed to an external component of the mechanism. The inner circumferential surface of the nut 10 has at least one annular groove section 102. In this embodiment, two annular groove sections 102 are used as an example.

[0038] like Figure 3A and Figure 3B As shown, the annular groove section 102 of the nut 10 has a plurality of annular grooves 102g and annular teeth 102t distributed circumferentially.

[0039] The inner circumferential surface of the nut 10 has at least one non-toothed section 103 located adjacent to the annular groove section 102. The non-toothed section 103 refers to the section of the inner circumferential surface of the nut 10 that does not have a toothed structure and has a relatively smooth surface. For example... Figure 3A As shown, a first groove 104 and a second groove 106 may be provided in the non-tooth section 103.

[0040] The inner circumferential surface of the nut 10 is also provided with at least one relief groove section 105. The relief groove section 105 is provided, for example, between two annular groove sections 102, and the relief groove section 105 has a larger inner diameter in the radial direction than the annular groove section 102.

[0041] The screw 20 is a long rod-shaped component, such as a long cylindrical shaft, which passes through the inner hole 100 of the nut 10 along the axial direction of the nut 10 and extends to the outside of the nut 10 to facilitate connection to a drive device or other external mechanism. The outer circumferential surface of the screw 20 is provided with a threaded structure 201 (also called a helical groove or helical teeth). In actual operation, the screw 20 can be driven to rotate by an external power source (not shown in the figure).

[0042] A plurality of rollers 30 are disposed in the inner hole 100 of the nut 10 and are arranged around the outer periphery of the screw 20 at intervals in the circumferential direction.

[0043] In the first embodiment of this utility model, a plurality of rollers 30 are respectively disposed at different circumferential positions on the outer periphery of the screw 20, and form rolling engagement with the thread structure 201 corresponding to each position. Although each roller 30 is generally similar in appearance, it is an independent component with individual identifiability, corresponding to the thread geometry of the screw 20 in different circumferential sections, thereby achieving multi-point independent and precise rolling engagement and further improving engagement stability.

[0044] like Figure 3A and Figure 3B As shown, each roller 30 has a plurality of annular teeth 30t and corresponding annular grooves 30g on its outer peripheral surface. The annular teeth 30t of the roller 30 may have a curved profile. This tooth design can improve the point contact stability between the roller 30 and the tooth surface of the nut 10 or screw 20 during the planetary rolling motion of the roller 30.

[0045] Each roller 30 has at least one large pitch diameter section 301 and at least one small pitch diameter section 302 along its axial direction. The pitch diameter of the large pitch diameter section 301 is larger than that of the small pitch diameter section 302. The large pitch diameter section 301 has annular teeth for rolling engagement with the thread structure 201 of the screw 20, while the small pitch diameter section 302 has annular teeth for rolling engagement with the annular groove section 102 of the nut 10. The large pitch diameter section 301 is positioned corresponding to the relief groove section 105, ensuring that the large pitch diameter section 301 of the roller 30 does not contact or interfere with the inner circumferential surface of the nut 10. The small pitch diameter section 302 is positioned corresponding to the annular groove section 102 of the nut 10, allowing its outer annular teeth to roll into engagement with the annular groove section 102. In this embodiment, each roller 30 is provided with a large pitch diameter section 301 and two small pitch diameter sections 302 located on both sides thereof, such as Figure 2 and Figure 3A As shown, each roller 30 has a smooth surface 302S in the small diameter section 302 at both ends of its axial direction, and its outer peripheral surface is not provided with a toothed structure.

[0046] With this structure, the rollers 30 can simultaneously establish rolling contact on both sides with the screw 20 and the nut 10, achieving stable bidirectional meshing during planetary motion. In addition, the annular groove section 102 of the nut 10 provides a circumferential guiding and restraining function, which allows the plurality of rollers 30 to be stably positioned on the inner circumferential surface of the nut 10, while preventing the plurality of rollers 30 from dislodging in the axial direction.

[0047] In actual operation, when the screw 20 is driven to rotate by an external power source, the plurality of rollers 30 can synchronously perform planetary rolling contact between the outer circumference of the screw 20 and the inner circumference of the nut 10, accompanied by a combined motion of rotation and revolution. Through the rolling engagement between the threaded structure 201 of the screw 20 and the large-pitch section 301 of the rollers 30, the rollers 30 can achieve planetary motion between the screw 20 and the nut 10, thereby converting the rotational motion of the screw 20 into its axial linear movement relative to the nut 10. Through this motion mechanism, each roller 30 can also share the axial load originally applied to the screw 20, thereby improving the durability and stability of the overall transmission structure.

[0048] Please see Figure 3A and Figure 4As shown, the retaining assembly 50 may include two integrally formed annular members 50r. The two annular members 50r are respectively disposed at opposite axial ends of the plurality of rollers 30, sleeved on the outer periphery of the screw 20, and engage with the non-toothed section 103 of the nut 10. Each annular member 50r has a through hole 500 in its center to allow the screw 20 to pass through. In actual operation, the two annular members 50r can rotate synchronously with the revolution of the rollers 30, and the positioning grooves 502 provided on them accommodate the two ends of the corresponding rollers 30 to maintain the circumferential spacing of the rollers 30.

[0049] like Figure 4 As shown, the retaining assembly 50 has a plurality of spaced-apart protrusions 501 on its periphery, which define a corresponding number of positioning grooves 502 at intervals. The groove profile of each positioning groove 502 corresponds to the shape of the axial end of the roller 30, and is used to accommodate the ends of the plurality of rollers 30 and stably position them in a specific circumferential position. With this configuration, the retaining assembly 50 can space the plurality of rollers 30 between the screw 20 and the nut 10, ensuring that they maintain their circumferential alignment during planetary rolling motion.

[0050] Please refer to the following: Figure 2 and Figure 3A As shown, the fixing member 60 is disposed in the inner hole 100 of the nut 10 and abuts against the side of the annular member 50r opposite to the plurality of rollers 30. The fixing member 60 can be an annular elastic fastener disposed in the second groove 106 provided on the inner circumferential surface of the nut 10, forming a locking engagement with the annular member 50r. The fixing member 60 is not a necessary component in this utility model, but its provision can further enhance the positioning stability of the retaining member assembly 50 in the nut 10, prevent the retaining member assembly 50 from axially shifting in the inner hole 100 of the nut 10 under long-term operation or external force, and further improve the structural stability of the overall transmission assembly. Whether or not to provide the fixing member 60 can be flexibly adjusted according to the actual usage scenario and structural requirements.

[0051] The friction elastic element 40 is, for example, a ring-shaped component, which can be made of a material with elastic and wear-resistant properties, such as rubber, engineering plastics, or elastic metal. Its shape is generally a circular ring structure with a certain thickness, so as to achieve radial interference fit with the outer periphery of the roller and maintain a stable contact state during operation.

[0052] A friction elastic element 40 is disposed on the non-toothed section 103 of the inner circumferential surface of the nut 10, and forms an interference contact with the smooth surface 302S of the small-diameter section 302 of the roller 30. Specifically, in the first embodiment of the present invention, the inner circumferential surface of the nut 10 is provided with a non-toothed section 103 without a toothed structure at the adjacent annular groove section 102, and each roller 30 is provided with a smooth surface 302S on the outer circumferential surface of the axial end of the small-diameter section 302, which serves as the contact corresponding surface of the friction elastic element 40. The non-toothed section 103 corresponds to the smooth surface 302S. By surrounding the friction elastic element 40 between the non-toothed section 103 and the smooth surfaces 302S, and forming a stable interference contact with each roller 30, radial preload can be applied to each roller 30. To ensure the reliability of the installation and positioning of the friction elastic element 40, a first groove 104 may be provided in the non-tooth section 103 of the nut 10 for the friction elastic element 40 to be embedded therein.

[0053] The coefficient of friction of the friction elastic element 40 can be designed and adjusted by parameters such as its material, contact area, thickness or elastic modulus, so as to properly control the rolling friction characteristics between the roller 30 and the nut 10 and further optimize the overall transmission performance.

[0054] Please see Figure 3C As shown, the present invention also discloses a second embodiment of a planetary roller screw transmission assembly, the main difference of which is that the position of the friction elastic element 40 is slightly different from that of the first embodiment, which is an example of another configuration.

[0055] In this embodiment, the friction elastic element 40 is still disposed in the non-toothed section 103 on the inner circumferential surface of the nut 10, and forms an interference contact with the smooth surface 302S of the small pitch diameter section 302 of the roller 30. Unlike the first embodiment, which places the friction elastic element 40 at the corresponding position at the axial end of the roller 30, this embodiment adds a non-toothed section 103 near the relief groove section 105, so that the friction elastic element 40 is moved closer to the middle section of the roller 30. This arrangement brings the friction elastic element 40 closer to the geometric center of the roller 30, allowing it to exhibit different force direction characteristics when radial preload is applied, and providing another design reference in practical applications, which helps technicians to make elastic adjustments according to system requirements.

[0056] Please see Figure 5 and Figure 6B As shown. Figure 5 As shown, the friction elastic element 40 is disposed on the non-tooth section 103 of the inner circumferential surface of the nut 10, and forms radial interference contact with the smooth surface 302S provided on the small diameter section 302 of the roller 30, thereby applying a stable radial preload F to the roller 30.

[0057] The radial preload F generated by this interference contact can further achieve the following two technical effects:

[0058] First, such as Figure 5 and Figure 6B As shown, the radial preload F, in its tangential component on the contact surface between the friction elastic element 40 and the roller 30, forms a static friction force F1. This static friction force F1 provides circumferential positioning for the roller 30, ensuring its rotation and revolution are always controlled within the designed pitch circle, preventing slippage or freewheeling, and helping to maintain the rolling contact stability between the roller 30 and the nut 10. It is worth noting that although the friction elastic element 40 is positioned between the roller 30 and the nut 10, it does not directly press the roller 30 against the tooth surface of the nut 10. The resulting static friction force F1 is sufficient to guide the roller 30 to maintain a pure rolling contact state, preventing slippage or freewheeling due to unstable movement or contact position misalignment. This further ensures that the rotational motion of the screw 20 is stably converted into axial linear movement relative to the nut 10.

[0059] Secondly, such as Figure 5 As shown, the radial preload F is also transmitted to the contact interface between the roller 30 and the screw 20 through the geometric configuration of the roller 30, thereby generating a component force along the normal direction, i.e., the positive force F2, at the contact point between the roller 30 and the screw 20. This positive force F2 can stably press the roller 30 against the tooth surface of the thread structure of the screw 20, compensate for the radial offset that may be caused by load changes or high-speed operation, further improve the contact pressure and meshing stability, and help improve the accuracy and reliability of the overall transmission system.

[0060] Please see Figure 6A As shown, in order to ensure that the friction elastic element 40 can accurately apply radial preload to the plurality of rollers 30 and establish a stable and consistent rolling contact relationship between the rollers 30 and the nut 10, the first embodiment of this utility model specifically performs geometric optimization design on the installation position of the friction elastic element 40 and the pitch circle diameter corresponding to its interference.

[0061] Specifically, the friction elastic element 40 forms an interference contact with the smooth surface 302S of the small-diameter section 302 of the roller 30. Through specific geometric design and machining precision control, the radial distance D1 from the interference contact position P1 to the geometric center of the nut 10 is essentially equivalent to the radial distance D2 from the rolling contact position P2 between the annular groove section 102 of the nut 10 and the small-diameter section 302 of the roller 30 to the geometric center of the nut 10. This design ensures that the radial preload applied by the friction elastic element 40 accurately corresponds to the meshing pitch circle position of the roller 30 and the nut 10, preventing contact point offset and thus maintaining the stability of the rolling contact.

[0062] Please see Figure 6A and Figure 6BAs shown, in the first embodiment of this utility model, in order to ensure that the roller 30 can achieve precise and stable rolling meshing between the screw 20 and the nut 10, a geometric structure design is specifically made for the pitch circle radius relationship corresponding to each meshing section, so that when the roller 30 makes rolling contact with the screw 20 and the nut 10, each contact point corresponds to the same designed pitch circle position, thereby establishing a continuous and synchronous rolling contact state, and further ensuring the meshing stability and planetary motion consistency of the roller 30 during operation.

[0063] like Figure 6A and Figure 6B As shown, the screw 20 is provided with a threaded structure 201. The radial distance from the point of rolling contact between the threaded structure 201 and the annular teeth (or annular groove) of the large pitch diameter section 301 of the roller 30 to the geometric center of the screw 20 is defined as the pitch circle radius Rs of the screw; the radial distance from the point of rolling contact between the annular teeth (or annular groove) of the large pitch diameter section 301 of the roller 30 and the threaded structure 201 of the screw to the geometric center of the roller is defined as the pitch circle radius Rps of the large pitch diameter section of the roller; the radial distance from the point of rolling contact between the annular teeth (or annular groove) of the small pitch diameter section 302 of the roller 30 and the annular groove section 102 on the inner circumference of the nut 10 to the geometric center of the roller is defined as the pitch circle radius Rpr of the small pitch diameter section of the roller; the radial distance from the point of rolling contact between the annular groove section 102 on the inner circumference of the nut 10 and the small pitch diameter section 302 of the roller 30 to the geometric center of the nut is defined as the pitch circle radius Rr of the nut. The first embodiment of this utility model specifically ensures that the pitch circle radii satisfy the following relationship: Rr = Rs + Rps + Rpr, thereby ensuring that when the roller 30 performs planetary motion consisting of its rotation and revolution, it can roll into contact with the screw 20 and the nut 10 at the same designed pitch circle position. Through this geometric correspondence, slippage or unstable contact problems caused by contact errors or assembly deviations can be effectively avoided, further improving the overall transmission stability.

[0064] In summary, the planetary roller screw transmission assembly provided by this invention utilizes the interference contact formed between the friction elastic element in the non-toothed section of the nut and the smooth surface of the small-pitch section of the roller to apply radial preload to the roller, thereby generating stable static friction. This structure provides an effective circumferential stabilization mechanism during the planetary motion of the roller's rotation and revolution, helping to suppress slippage or wobbling of the roller during movement, further ensuring that the roller and nut maintain pure rolling contact. Furthermore, this radial preload also generates a positive force towards the screw, increasing the contact force between the roller and the screw, thereby enhancing the rolling meshing stability of the roller, nut, and screw on both sides, effectively suppressing instability such as slippage or freewheeling, and thus improving overall transmission accuracy and reliability.

[0065] Furthermore, through geometric optimization design of the installation position of the friction elastic element and its corresponding interference pitch circle radius, the radial preload can be precisely applied to the meshing pitch circle position of the roller and nut. In addition, by utilizing the mutual geometric relationship between the corresponding meshing pitch circle radii of the roller, screw, and nut, all rolling contact points are consistently positioned on the designed pitch circle, effectively improving rolling meshing accuracy and transmission efficiency.

[0066] The present invention has been described in detail above. However, the above description is only a preferred embodiment of the present invention and should not be construed as limiting the scope of implementation of the present invention. All equivalent variations and modifications made based on the technical concept of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A planetary roller screw drive assembly, characterized by, The nut has an inner hole axially extending therethrough, and an inner periphery of the nut is provided with at least one annular groove segment and at least one non-toothed segment adjacent to the annular groove segment. The screw rod has a threaded structure on an outer periphery thereof. The plurality of rollers are arranged in the inner hole of the nut and configured to the outer periphery of the screw rod, and each roller has an outer periphery provided with a plurality of annular teeth, and each roller has at least one large pitch segment and at least one small pitch segment with a smooth surface in the axial direction, the large pitch segment is provided with annular teeth for rolling engagement with the screw rod, and the small pitch segment is provided with annular teeth for rolling engagement with the nut. The retaining member set is arranged at the axial end of the plurality of rollers to maintain the circumferential spacing of the plurality of rollers. At least one frictional elastic member is arranged on the non-toothed segment of the inner periphery of the nut and interferes with the smooth surface of the small pitch segment of the plurality of rollers. The inner periphery of the nut is further provided with at least one retreat groove segment corresponding to the position of the large pitch segment of the plurality of rollers.

2. The planetary roller screw assembly of claim 1, wherein, The inner periphery of the nut is provided with a first groove in the non-toothed segment, and the frictional elastic member is embedded in the first groove.

3. The planetary roller screw assembly of claim 1, wherein, The radial distance from the contact point of the frictional elastic member and the smooth surface of the small pitch segment of the roller to the geometric center of the nut is equal to the radial distance from the contact point of the annular groove segment of the nut and the small pitch segment of the roller to the geometric center of the nut.

4. The planetary roller screw assembly of claim 1, wherein, The screw rod has a pitch radius Rs, which is the radial distance from the contact point of the threaded structure of the screw rod and the large pitch segment of the roller to the geometric center of the screw rod; the large pitch segment of the roller has a pitch radius Rps, which is the radial distance from the contact point of the annular teeth of the large pitch segment and the threaded structure of the screw rod to the geometric center of the roller; the small pitch segment of the roller has a pitch radius Rpr, which is the radial distance from the contact point of the annular teeth of the small pitch segment and the annular groove segment of the nut to the geometric center of the roller; the nut has a pitch radius Rr, which is the radial distance from the contact point of the annular groove segment of the nut and the small pitch segment of the roller to the geometric center of the nut; the pitch radii satisfy the following relationship: Rr=Rs+Rpr+Rps.

5. The planetary roller screw assembly of claim 1, wherein, The retaining member set includes two ring members, which are sleeved on the screw rod and arranged at the axial ends of the plurality of rollers, respectively, to jointly maintain the circumferential spacing of the plurality of rollers.

6. The planetary roller screw assembly of claim 1, wherein, The ring member is provided with a plurality of positioning grooves, each of which is used to accommodate the axial end of a corresponding roller to maintain the circumferential spacing of the plurality of rollers.

7. The planetary roller screw assembly of claim 6, wherein, At least one fixing member is arranged in the inner hole of the nut and abuts against the side of the ring member away from the plurality of rollers to limit the axial displacement of the retaining member set in the nut.

8. The planetary roller screw assembly of claim 7, wherein: ​

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