Roller screw bidirectional staggered pre-pressing structure with built-in elastic sheet

Abstract

The utility model provides a roller screw bidirectional staggered pre-pressing structure with a built-in elastic sheet, the outer peripheral surface of a screw is provided with a thread structure, a nut is sleeved on the screw, and the inner peripheral surface of the screw is provided with an annular groove section and two limiting grooves. The roller set is arranged between the screw and the nut and comprises a first roller and a second roller which are arranged in a staggered mode, the periphery of each roller is provided with annular teeth, and the annular teeth are meshed with the threaded structure and the annular groove section respectively. The two retaining pre-pressing units are respectively arranged at two opposite ends of the roller group, each retaining pre-pressing unit comprises a retainer and an elastic sheet, the two retainers are respectively provided with a plurality of retaining holes for respectively accommodating the positioning ends of the rollers, and the elastic sheet is provided with elastic upwarp feet which are radially staggered relative to the retaining holes and are respectively propped against the tips of the rollers. Therefore, axial pre-pressing forces in opposite directions are respectively applied to the first roller and the second roller, a bidirectional staggered pre-pressing effect is formed, a gap is compensated, and the transmission precision and the movement stability are improved.

Description

Technical Field

[0001] This utility model relates to a transmission component, and more particularly to a roller screw bidirectional staggered preload structure with built-in springs that can generate axial preload on the rollers to improve rolling stability. Background Technology

[0002] Planetary roller screw drives (also known as planetary roller screws) feature high load-bearing capacity, high rigidity, excellent transmission efficiency, and positioning accuracy. They are widely used in precision machine tools, servo drive systems, aerospace control devices, and high-performance robots—applications requiring rapid response and high dynamic performance. Their basic structure utilizes a plurality of rollers positioned between a screw and a nut, wound around the outer circumference of the screw. Through the rolling engagement of the rollers between the screw and nut, rotational motion is converted into linear translation, thereby driving an external load.

[0003] like Figure 1A As shown, a typical planetary roller screw drive includes a screw 11, a nut 12, a plurality of rollers 13, and a retainer assembly 14. The screw 11 has an external thread structure, and the nut 12 has an inner hole 120 for accommodating the plurality of rollers 13, and an annular tooth structure 12t is provided on the inner circumference of the nut 12 for meshing with the outer annular teeth of the rollers 13 to form rolling contact. The retainer assembly 14 is disposed on 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 their circumferential spacing.

[0004] However, in actual operation, the aforementioned traditional devices still have several problems. For example... Figure 1B and Figure 1C As shown, the geometric fit between roller 13, screw 11, and nut 12 is extremely precise. However, due to manufacturing tolerances and assembly errors, a small gap G is generated between roller 13 and screw 11 / nut 12, causing the actual contact position of roller 13 to deviate from the designed pitch circle radius. If this complex fit gap G is not effectively compensated, there will be insufficient friction between roller 13 and nut 12 during operation, resulting in slippage or freewheeling, making it difficult to maintain pure rolling contact and causing sliding friction. This leads to greater wear on roller 13 and reduces the overall structural life. Similarly, insufficient contact may also cause slippage between roller 13 and screw 11, thereby disrupting the deceleration and propulsion effect of planetary motion, resulting in a decrease in linear propulsion efficiency and positioning accuracy.

[0005] Furthermore, although the existing retainer assembly 14 can limit the ends and control the angle distribution of the roller 13, the component only has a mechanical positioning function and cannot provide preload compensation or guide the direction of roller movement, nor can it effectively improve the sliding offset problem of the roller 13 caused by the clearance G.

[0006] Therefore, how to effectively improve the stability of the contact between the roller 13 and the nut 12 without increasing structural complexity and manufacturing cost, and strengthen the rolling engagement between the roller 13 and the screw 11, so as to ensure that the screw 11, roller 13 and nut 12 maintain stable rolling motion, is an important issue that needs to be overcome in this field. Utility Model Content

[0007] The purpose of this invention is to provide a bidirectional staggered preload structure for a roller screw with built-in springs that can solve the above-mentioned technical problems. It can effectively compensate for the fit clearance caused by machining errors, and apply axial preload in opposite directions to the two types of staggered rollers to achieve a stable bidirectional rolling contact effect, thereby improving the overall transmission efficiency, reducing wear, and extending service life.

[0008] To achieve the above objectives, this utility model provides a bidirectional staggered preload structure for a roller screw with a built-in spring sheet, characterized in that it includes:

[0009] A screw with a threaded structure on its outer circumference;

[0010] A nut is fitted onto the screw, and its inner circumferential surface is provided with at least one annular groove section and two limiting grooves;

[0011] A roller assembly is disposed between the screw and the nut, having a plurality of first rollers and a plurality of second rollers arranged in an alternating pattern. Each of the first rollers has a first positioning end and a first tip at both ends, and each of the second rollers has a second positioning end and a second tip at both ends opposite to those of the first rollers. Each roller has an annular tooth on its outer periphery, which meshes with the thread structure and the annular groove section.

[0012] Two retaining preload units are disposed inside the nut and located at both ends of the roller assembly. Each retaining preload unit includes a retainer and a spring plate. The retainer has a plurality of retaining holes, and the retaining holes of the two retainers respectively accommodate the first positioning end and the second positioning end. The spring plate is disposed between the inner side of the retainer and the roller assembly, and forms a plurality of elastic protrusions that tilt and rise towards the roller assembly in the circumferential direction. The elastic protrusions are radially offset relative to the retaining holes, and the elastic protrusions of the two spring plates elastically abut against the first tip and the second tip, respectively.

[0013] A fastener assembly has two fasteners respectively disposed on the outside of the two retaining preload units and embedded in the limiting groove, for axially limiting the two retaining preload units within the nut;

[0014] By radially misaligning the plurality of elastic pawls with the plurality of retaining holes, the first tip and the second tip respectively abut against the elastic pawls of the two spring pieces, thereby causing the elastic pawls to elastically deform. This results in the first positioning end and the second positioning end forming a first gap and a second gap with the bottom of the corresponding retaining hole, respectively. The first tip and the second tip respectively transmit preload in opposite directions, applying axial preload in opposite directions to the first roller and the second roller. This creates bidirectional staggered preload at both ends of the roller assembly, reducing the backlash between the screw and the nut and maintaining pure rolling contact of the rollers.

[0015] The roller screw bidirectional staggered preload structure with built-in spring sheet includes: the retainer is provided with a plurality of fitting grooves, the spring sheet is an annular spring sheet, and the outer edge of the spring sheet is provided with a plurality of fitting feet, which are correspondingly embedded in the plurality of fitting grooves to achieve detachable positioning.

[0016] The roller screw bidirectional staggered preload structure with built-in spring sheet, wherein: each of the plurality of elastic feet of the spring sheet is provided with a groove, and the first tip and the second tip respectively correspond to the groove.

[0017] The roller screw bidirectional staggered preload structure with built-in spring sheet, wherein: the groove is an arc-shaped groove or a conical groove; the first tip and the second tip are conical and form point contact with the groove.

[0018] The roller screw bidirectional staggered preload structure with built-in spring sheet, wherein: the plurality of elastic raised feet are arranged radially at intervals and are in a raised state when not under force.

[0019] The roller screw bidirectional staggered preload structure with built-in spring sheet, wherein: a bearing is provided between the preload holding unit and the fastener.

[0020] The roller screw bidirectional staggered preload structure with built-in spring sheet, wherein: the retainer and the spring sheet are integrally formed.

[0021] A bidirectional staggered preload structure for a roller screw with built-in spring sheet, characterized in that it comprises:

[0022] A screw with a threaded structure on its outer circumference;

[0023] A nut is fitted onto the outside of the screw, and its inner circumferential surface is provided with at least one annular groove section and two limiting grooves;

[0024] A roller assembly is disposed between the screw and the nut, having a plurality of first rollers and a plurality of second rollers arranged in an alternating pattern. Each first roller has a first positioning end and a first tip at its opposite ends, and each second roller has a second positioning end and a second tip at its opposite ends, opposite to the ends of the first roller. Each roller has an annular tooth on its outer periphery, which meshes with the thread structure and the annular groove section respectively.

[0025] Two retaining preload units are respectively disposed at opposite ends of the roller assembly. Each retaining preload unit includes a spring sheet. The spring sheet has a plurality of positioning holes and a plurality of elastic feet that tilt and rise towards the roller assembly. The positioning holes of the two spring sheets respectively accommodate the first positioning end and the second positioning end. The elastic feet of the two spring sheets are radially offset relative to the positioning holes and elastically abut against the corresponding first tip and second tip, respectively.

[0026] A fastener assembly has two fasteners, which are respectively disposed on the outside of the two retaining preload units and embedded in the limiting groove, for fixing the two retaining preload units and axially limiting them within the nut;

[0027] By radially misaligning the elastic spring and the positioning hole, the first tip and the second tip respectively abut against the elastic spring of the two spring pieces, causing the elastic spring to deform elastically. This results in the first positioning end and the second positioning end forming a first gap and a second gap with the corresponding positioning hole, respectively. The first tip and the second tip respectively transmit preload in opposite directions, applying axial preload in opposite directions to the first roller and the second roller. This creates bidirectional staggered preload at both ends of the roller assembly, reducing backlash between the screw and the nut and maintaining pure rolling contact of the rollers.

[0028] The roller screw bidirectional staggered preload structure with built-in spring sheet, wherein: the elastic spring has a free end, the free end is provided with a groove, and the groove forms point contact with the corresponding first tip or second tip.

[0029] The roller screw bidirectional staggered preload structure with built-in spring sheet, wherein: the groove is an arc-shaped groove or a conical groove; the first tip and the second tip are conical and form point contact with the groove.

[0030] The roller screw bidirectional staggered preload structure with built-in spring sheet, wherein: a bearing or a washer is provided between each spring sheet and the fastener.

[0031] The spring and retainer of the preload unit are designed to be detachable for easy maintenance and replacement; alternatively, they can be a one-piece molded structure to simplify the assembly process and reduce the number of parts.

[0032] By directly providing positioning functionality through the spring body of each preload retaining unit, the retainer structure can be omitted, thereby simplifying component construction and reducing assembly time. The number of elastic spring feet on each spring corresponds to the total number of the first and second rollers, and they are arranged circumferentially to ensure that each roller receives uniform and independent preload. The positioning hole of the spring in each preload retaining unit forms an external opening on the outer surface of the spring. The first and second positioning ends have an axial difference from the external opening, so that the first and second positioning ends are hidden within the external opening to avoid contact between the first and second positioning ends and the gaskets or bearings on the outside of the spring, and to form functionally staggered first and second gaps.

[0033] Through the above structural design, this invention can effectively compensate for the fit clearance caused by manufacturing and assembly errors, prevent the rollers from sliding and shifting during movement, reduce friction, and improve motion accuracy. The staggered bidirectional preload structure simultaneously enhances the stability and fit of the rollers in both directions, further ensuring the transmission system possesses excellent precision and reliability under high load and high dynamic motion conditions. Attached Figure Description

[0034] Figure 1A This is a schematic diagram of an existing planetary roller screw drive.

[0035] Figure 1B for Figure 1A Schematic diagram of the meshing contact relationship between the middle roller and the nut;

[0036] Figure 1C for Figure 1A Schematic diagram of the meshing contact relationship between the intermediate roller and the screw;

[0037] Figure 2 This is an exploded perspective view of an embodiment of the present utility model;

[0038] Figure 3A This is a schematic cross-sectional view of an embodiment of the present utility model;

[0039] Figure 3B for Figure 3A A magnified view of a portion of the image;

[0040] Figure 3C for Figure 3A Right-side sectional view;

[0041] Figure 3D To maintain the three-dimensional schematic diagram of the preload unit;

[0042] Figure 4 This is a schematic diagram of the first roller and the second roller in an embodiment of this utility model;

[0043] Figure 5AThis is a schematic diagram illustrating how the preload retaining elements at both ends of the roller assembly generate axial preload in opposite directions on the plurality of first and second rollers in this embodiment of the present invention.

[0044] Figure 5B This is an enlarged schematic diagram of an arc-shaped groove;

[0045] Figure 5C This is an enlarged schematic diagram of a conical groove;

[0046] Figure 6A and Figure 6B This is a schematic diagram of the second roller pushing to the right in an embodiment of the present invention;

[0047] Figure 7A and Figure 7B This is a schematic diagram showing the first roller pushing to the left in an embodiment of the present invention;

[0048] Figure 8 A schematic diagram showing the selection of a bearing between the preload unit and the fastener in this utility model;

[0049] Figures 9A to 9D This is a schematic diagram illustrating the implementation of the pre-compression unit variation according to this utility model.

[0050] Explanation of reference numerals in the attached drawings: Screw 21; Threaded structure 211; Nut 22; Inner hole 220; Annular groove section 221; Annular groove 221g; Limiting groove 222; Relief groove section 223; Roller assembly R; First roller 23; Annular tooth 23t; First meshing section 231; Second meshing section 232; First positioning end 233; First tip 234; Second roller 24; Annular tooth 24t; First meshing section 241 Second engagement section 242; Second positioning end 243; Second tip 244; Preload retainer unit K; Retainer 26; Retaining hole 261; Fitting groove 262; Spring piece 27, 27a; Elastic lifting foot 271, 271a; Groove 271r, 271ra; Fitting foot 272; Positioning hole 273a; Outer opening 2731a; Fastener assembly C; Fastener 29; First gap 31; Second gap 32; Bearing 33. Detailed Implementation

[0051] The structure and functional characteristics of the bidirectional staggered preload structure of the roller screw with built-in spring sheet of this utility model will be described with reference to the preferred embodiment in the accompanying drawings.

[0052] Please see Figure 2 , Figures 3A-3D , Figure 4 and Figures 5A to 5C As shown, a preferred embodiment of the present invention includes a bidirectional staggered preload structure with a built-in spring sheet and roller screw, comprising: a screw 21, a nut 22, a roller assembly R, two preload holding units K, and a fastener assembly C.

[0053] The nut 22 may be a hollow cylindrical component with an inner hole 220 extending through both ends along its axial direction. The inner circumferential surface of the nut 22 has two annular groove sections 221 for rolling engagement with the roller assembly R. These multiple annular groove sections 221 provide circumferential guidance and contact restraint, allowing the roller assembly R to roll stably within the nut 22 in a planetary manner and preventing it from disengaging in the axial direction. Each annular groove section 221 has multiple circumferentially distributed annular grooves 221g, and a limiting groove 222 is provided at each end adjacent to the ungrooved areas.

[0054] In addition, the inner circumferential surface of the nut 22 is provided with a radial relief groove section 223 between the two annular groove sections 221. The inner diameter of the relief groove section 223 is larger than the inner diameter of other parts to provide sufficient space to avoid interference between the roller assembly R and the inner wall.

[0055] The screw 21 is a long rod-shaped component, such as a long cylindrical shaft, which passes coaxially through the inner hole 220 of the nut 22 along its axial direction. At least one end extends outside the nut 22 for connecting to a drive device or mounting to other external mechanisms. The outer circumferential surface of the screw 21 has a threaded structure 211 (also called a helical groove or helical teeth), which can be a multi-start thread. In actual operation, the screw 21 can be driven to rotate by an external power source (not shown in the figure), and through the double-sided meshing between its threaded structure 211 and the roller assembly R, the roller assembly R simultaneously rotates and revolves between the screw 21 and the nut 22 in a planetary rolling motion. In this way, the rotational motion of the screw 21 can be converted into its axial linear movement relative to the nut 22, thereby achieving a highly efficient and precise linear driving effect.

[0056] Please refer to the following: Figure 2 , Figures 3A-3C and Figure 4 As shown, the roller assembly R is disposed in the inner hole 220 of the nut 22 and located between the nut 22 and the screw 21, including a plurality of staggered first rollers 23 and second rollers 24. The plurality of first rollers 23 and second rollers 24 are arranged around the outer periphery of the screw 21 at uniform intervals along the circumference. In this embodiment, the number of first rollers 23 and second rollers 24 is selected to be three each, correspondingly arranged at different circumferential angular positions on the outer periphery of the screw 21, and forming rolling engagement with the corresponding thread structure 211. Thus, driven by the rotation of the screw 21, the roller assembly R can move in a planetary rolling motion between the screw 21 and the nut 22.

[0057] The first roller 23 and the second roller 24 are each an axially extending cylindrical member, with a plurality of annular teeth 23t and 24t on their outer circumferential surfaces to engage with corresponding structures on the screw 21 and the nut 22. Specifically, each of the first roller 23 and the second roller 24 is divided along its axial direction into at least one first engagement section 231 and 241 and at least one second engagement section 232 and 242, wherein the diameter of the first engagement section 231 and 241 is larger than the diameter of the second engagement section 232 and 242. The annular teeth 23t and 24t of the first engagement sections 231 and 241 are used for rolling engagement with the thread structure 211 of the screw 21, and the annular teeth 23t and 24t of the second engagement sections 232 and 242 are used for rolling engagement with the annular groove 221g of the annular groove section 221 of the nut 22.

[0058] like Figure 3A and Figure 4 As shown, the first engagement sections 231 and 241 are located in the axial middle section of the first roller 23 and the second roller 24, respectively, and each end of the first engagement section 232 and 242 is provided with a second engagement section 232 and 242, thereby forming a double-sided rolling engagement relationship with the screw 21 and the nut 22. Furthermore, to avoid interference between the first engagement sections 231 and 241 and the inner wall of the nut 22, these sections are correspondingly arranged in the relief groove section 223 of the nut 22, providing sufficient radial space so that it only contacts the screw 21 and participates in rolling.

[0059] Each first roller 23 has a first positioning end 233 and a first tip 234 formed at its opposite ends, and each second roller 24 has a second positioning end 243 and a second tip 244 formed at its opposite ends, opposite to the ends of the first roller 23. In this embodiment, the first positioning end 233 and the first tip 234 are located at the left and right ends of the first roller 23, and the second positioning end 243 and the second tip 244 are located at the right and left ends of the second roller 24. The first tip 234 and the second tip 244 may be conical (conical) in shape.

[0060] Please refer to the following: Figure 2 and Figure 3A , Figure 3D , Figure 4 , Figure 5A , Figure 5B and Figure 5CPreload retaining units K are respectively disposed at opposite ends of the roller assembly R. Each preload retaining unit K includes a retainer 26 and a spring piece 27. Each retainer 26 has a plurality of retaining holes 261 and a plurality of fitting grooves 262. The plurality of retaining holes 261 are radially distributed on the inner side of the retainer 26 to respectively accommodate the corresponding first positioning end 233 and second positioning end 243, so as to stabilize the angular spacing of the plurality of first and second rollers 23, 24 in the circumferential direction. The plurality of fitting grooves 262 are disposed on the periphery of the retainer 26. Each spring piece 27 (e.g., annular spring piece) is disposed between the inner side of the retainer 26 and the roller assembly R, forming a plurality of elastic upturned feet 271 tilted towards the roller assembly R in the circumferential direction (e.g., the inner circumferential direction). These multiple elastic upturned feet 271 are arranged radially at intervals, and their number is equal to the total number of the first roller 23 or the second roller 24 (e.g., three for each roller, corresponding to three elastic upturned feet 271), and are arranged circumferentially to ensure that each first roller 23 and second roller 24 receives uniform preload. Before assembly, the elastic upturned feet 271 are in an uncompressed upturned state and are radially offset relative to the retaining hole 261. This uncompressed upturned state helps to provide effective elastic preload after assembly, ensuring that each first roller 23 and second roller 24 receives uniform force and enhancing stability. The outer edge of the spring piece 27 is provided with a plurality of engaging feet 272, which are correspondingly embedded into the engaging grooves 262 of the retainer 26 for detachable positioning assembly. Not limited to this, the retainer 26 and the spring 27 can also be integrally formed.

[0061] Furthermore, each of the free ends of the plurality of elastic hinges 271 is provided with a groove 271r to allow the first tip 234 to abut against the second tip 244. The groove 271r can be an arc-shaped groove (e.g., Figure 5B (as shown) or conical groove (such as) Figure 5C (As shown in the diagram). The conical first tip 234 and second tip 244 form point contact with the groove 271r during assembly. This helps to provide sufficient positioning function and concentrated preload transmission for the first and second rollers 23 and 24, and significantly reduces the friction area between them, increasing the rotation efficiency of the first and second rollers 23 and 24.

[0062] The fastener assembly C includes two fasteners 29 (e.g., C-shaped or O-shaped fasteners), which are respectively disposed on the outside of the two retaining preload units K and embedded in the limiting groove 222 on the inner circumferential surface of the nut 22 to fix the two retaining preload units K and axially limit them inside the nut 22 to prevent them from falling off or moving axially during operation.

[0063] like Figure 2 , Figure 3A , Figure 4 , Figures 5A to 5CAs shown, after assembly, a first gap 31 is formed between the first positioning end 233 of the first roller 23 and the bottom of the retaining hole 261 of the retainer 26 at the right end. The first tip 234 abuts against the elastic foot 271 of the spring piece 27 at the left end, causing it to be pressed and undergo elastic deformation. Similarly, a second gap 32 is formed between the second positioning end 243 of the second roller 24 and the bottom of the retaining hole 261 of the retainer 26 at the left end. The second tip 244 abuts against the elastic foot 271 of the spring piece 27 at the right end, also causing elastic deformation. By having the first tip 234 and the second tip 244 abut against the spring pieces 27 at the left and right ends respectively, the groove 271r of the elastic foot 271 makes point contact with the first tip 234 and the second tip 244, resulting in elastic deformation. Furthermore, by combining the first gap 31 and the second gap 32, which are staggered at opposite ends of the roller assembly R, axial preload is applied to the first roller 23 and the second roller 24 in opposite directions, thus achieving a bidirectional staggered preload structure and enabling selective control of the preload transmission direction.

[0064] like Figure 6A and Figure 6B As shown, in Figure 5A The preload applied by the elastic foot 271 of the spring plate 27 at the left end is directly transmitted to the first roller 23 through the first tip 234. This, combined with the first gap 31 between the roller and the retainer 26 at the right end, pushes the first roller 23 to the right. This causes its annular teeth 23t to abut against the left side of the threaded structure 211 of the screw 21 and the left side of the annular groove 221g of the nut 22, creating a stable meshing contact and preventing slippage and freewheeling.

[0065] Similarly, such as Figure 7A and Figure 7B As shown, in Figures 5A to 5C The preload generated by the elastic spring foot 271 of the right-hand end spring 27 is directly transmitted to the second roller 24 through the second tip 244, and, in conjunction with the second gap 32 between it and the left-hand retainer 26, pushes the second roller 24 to the left. This causes its annular teeth 24t to abut against the right side of the thread structure 211 of the screw 21 and the right side of the annular groove 221g of the nut 22, forming a stable rolling engagement and effectively preventing slippage and freewheeling.

[0066] This invention utilizes two preload retaining units K, respectively positioned at both ends of the roller assembly R, to precisely guide the transmission path of the axial preload. This ensures that each elastic rest 271 acts only on specific first and second rollers 23 and 24, thereby applying positive preload in opposite directions to the first roller 23 and the second roller 24. This design ensures that all first and second rollers 23 and 24 are tightly pressed against the corresponding rolling contact surfaces of the screw 21 and nut 22, eliminating gaps caused by manufacturing tolerances. This effectively reduces sliding friction, minimizes backlash, improves the pure rolling stability of the rollers and overall transmission accuracy, and extends the system's service life.

[0067] Please continue to refer to this. Figure 8 As shown, this invention allows for the additional provision of a bearing 33 (e.g., ball, roller, or needle bearing) between the preload unit K and the fastener 29. This bearing 33 forms a stable rotating contact surface, reducing frictional resistance and improving rotational smoothness, thereby reducing energy loss and nonlinear deviation during pressure application. This not only maintains a stable preload effect but also improves the overall efficiency and stability of preload transmission. The bearing 33 can also absorb minor vibrations caused by preload, enhancing the dynamic stability of the transmission system.

[0068] Please see Figures 9A to 9D As shown, in another preferred embodiment, the bidirectional staggered preload structure of the roller screw with built-in spring sheet has a main structure that is basically the same as that of the aforementioned embodiment, and the same components and connection relationships will not be described again. The difference in this embodiment is that each retaining preload unit K located at both ends of the roller group R includes a spring sheet 27a (e.g., an annular spring sheet), omitting the retainer. The spring sheet 27a has a plurality of elastic lifting feet 271a tilted and raised towards the roller group R and a plurality of positioning holes 273a along its circumference (e.g., the inner circumferential direction). The structure of the elastic lifting foot 271a in this embodiment is the same as that of the elastic lifting foot 271 in the previous embodiment. The free end of the elastic lifting foot 271a is provided with a groove 271ra (which can be an arc-shaped groove, a conical groove, or a geometric design). The number of elastic feet 271a is equal to the total number of the first rollers 23 or the second rollers 24 (e.g., three elastic feet 271a for each of the three rollers), and they are arranged circumferentially to ensure that each first roller 23 or each second roller 24 receives uniform preload. The elastic feet 271a are radially offset relative to the positioning holes 273a to ensure that the preload is effectively applied to the first tip 234 and the second tip 244, while maintaining the stable positioning of the roller group R. The positioning holes 273a respectively accommodate the first positioning end 233 and the second positioning end 243. The first positioning end 233 forms a first gap 31 with the positioning hole 273a of the right end spring piece 27a; the second positioning end 243 forms a second gap 32 with the positioning hole 273a of the left end spring piece 27a.

[0069] Each spring piece 27a has a positioning hole 273a forming an outer opening 2731a on its outer side. The first positioning end 233 and the second positioning end 243, which are pivotally connected in the positioning hole 273a, have an axial difference from the outer opening 2731a, so that the first and second positioning ends 233 and 243 are hidden in the outer opening 2731a and do not contact the outer bearing 33, thus forming the first and second gaps 31 and 32.

[0070] The retaining preload unit K in this embodiment omits the retainer of the previous embodiment and is directly composed of a spring piece 27a with an elastic hinge 271a and a positioning hole 272a, thereby simultaneously achieving the dual functions of positioning and preload of the roller assembly R. When a bearing 33 is provided between the retaining preload unit K and the fastener 29, as described above, the bearing 33 can improve rotational smoothness and absorb vibration. If the bearing 33 is omitted, a shim (not shown) can be provided. This shim can be an annular metal or non-metal part, placed between the retaining preload unit K and the fastener 29 to increase the contact area, making the retaining preload unit K stably positioned and preventing external forces from affecting the preload effect. At the same time, the first and second positioning ends 233 and 243, which have an axial difference from the outer opening 2731a, do not contact the shim.

[0071] In summary, the bidirectional staggered preload structure of the roller screw with built-in spring sheets of this utility model achieves this by configuring preload holding units K at both ends of the roller assembly R. Through the elastic rests 271 and 271a of the spring sheets 27 and 27a, and the staggered arrangement of the first gap 31 and the second gap 32, the first roller 23 and the second roller 24 are subjected to preload forces in opposite directions, thus establishing a bidirectional force application mechanism with staggered configuration. This structure not only effectively compensates for clearances caused by machining tolerances and eliminates initial backlash, but also stabilizes the movement trajectories of the first and second rollers 23 and 24, ensuring they maintain a pure rolling state and effectively suppressing sliding friction and idling.

Claims

1. A bidirectional staggered preload structure for a roller screw with built-in spring sheet, characterized in that, include: A screw with a threaded structure on its outer circumference; A nut is fitted onto the screw, and its inner circumferential surface is provided with at least one annular groove section and two limiting grooves; A roller assembly is disposed between the screw and the nut, having a plurality of first rollers and a plurality of second rollers arranged in an alternating pattern. Each of the first rollers has a first positioning end and a first tip at both ends, and each of the second rollers has a second positioning end and a second tip at both ends opposite to those of the first rollers. Each roller has an annular tooth on its outer periphery, which meshes with the thread structure and the annular groove section. Two retaining preload units are disposed inside the nut and located at both ends of the roller assembly. Each retaining preload unit includes a retainer and a spring plate. The retainer has a plurality of retaining holes, and the retaining holes of the two retainers respectively accommodate the first positioning end and the second positioning end. The spring plate is disposed between the inner side of the retainer and the roller assembly, and forms a plurality of elastic protrusions that tilt and rise towards the roller assembly in the circumferential direction. The elastic protrusions are radially offset relative to the retaining holes, and the elastic protrusions of the two spring plates elastically abut against the first tip and the second tip, respectively. A fastener assembly has two fasteners respectively disposed on the outside of the two retaining preload units and embedded in the limiting groove, for axially limiting the two retaining preload units within the nut; By radially misaligning the plurality of elastic pawls with the plurality of retaining holes, the first tip and the second tip respectively abut against the elastic pawls of the two spring pieces, thereby causing the elastic pawls to elastically deform. This results in the first positioning end and the second positioning end forming a first gap and a second gap with the bottom of the corresponding retaining hole, respectively. The first tip and the second tip respectively transmit preload in opposite directions, applying axial preload in opposite directions to the first roller and the second roller. This creates bidirectional staggered preload at both ends of the roller assembly, reducing the backlash between the screw and the nut and maintaining pure rolling contact of the rollers.

2. The roller screw bidirectional staggered preload structure with built-in spring sheet as described in claim 1, characterized in that: The retainer is provided with a plurality of fitting slots, the spring is an annular spring, and the outer edge of the spring is provided with a plurality of fitting feet, which are correspondingly inserted into the plurality of fitting slots to achieve detachable positioning.

3. The roller screw bidirectional staggered preload structure with built-in spring sheet as described in claim 1, characterized in that: The spring has a groove on each of its multiple elastic feet, and the first tip and the second tip are respectively aligned with the groove.

4. The bidirectional staggered preload structure of the roller screw with built-in spring sheet as described in claim 3, characterized in that: The groove is an arc-shaped groove or a conical groove; the first tip and the second tip are conical and make point contact with the groove.

5. The bidirectional staggered preload structure of the roller screw with built-in spring sheet as described in claim 1, characterized in that: The multiple elastic feet are arranged radially at intervals and are in a raised state when not under force.

6. The roller screw bidirectional staggered preload structure with built-in spring sheet as described in claim 1, characterized in that: A bearing is provided between the preload retaining unit and the fastener.

7. The bidirectional staggered preload structure of the roller screw with built-in spring sheet as described in claim 1, characterized in that: The retainer and the spring are integrally formed.

8. A bidirectional staggered preload structure for a roller screw with built-in spring sheet, characterized in that, include: A screw with a threaded structure on its outer circumference; A nut is fitted onto the outside of the screw, and its inner circumferential surface is provided with at least one annular groove section and two limiting grooves; A roller assembly is disposed between the screw and the nut, having a plurality of first rollers and a plurality of second rollers arranged in an alternating pattern. Each first roller has a first positioning end and a first tip at its opposite ends, and each second roller has a second positioning end and a second tip at its opposite ends, opposite to the ends of the first roller. Each roller has an annular tooth on its outer periphery, which meshes with the thread structure and the annular groove section respectively. Two retaining preload units are respectively disposed at opposite ends of the roller assembly. Each retaining preload unit includes a spring sheet. The spring sheet has a plurality of positioning holes and a plurality of elastic feet that tilt and rise towards the roller assembly. The positioning holes of the two spring sheets respectively accommodate the first positioning end and the second positioning end. The elastic feet of the two spring sheets are radially offset relative to the positioning holes and elastically abut against the corresponding first tip and second tip, respectively. A fastener assembly has two fasteners, which are respectively disposed on the outside of the two retaining preload units and embedded in the limiting groove, for fixing the two retaining preload units and axially limiting them within the nut; By radially misaligning the elastic spring and the positioning hole, the first tip and the second tip respectively abut against the elastic spring of the two spring pieces, causing the elastic spring to deform elastically. This results in the first positioning end and the second positioning end forming a first gap and a second gap with the corresponding positioning hole, respectively. The first tip and the second tip respectively transmit preload in opposite directions, applying axial preload in opposite directions to the first roller and the second roller. This creates bidirectional staggered preload at both ends of the roller assembly, reducing backlash between the screw and the nut and maintaining pure rolling contact of the rollers.

9. The bidirectional staggered preload structure of the roller screw with built-in spring sheet as described in claim 8, characterized in that: The elastic foot has a free end with a groove that makes point contact with the corresponding first or second tip.

10. The roller screw bidirectional staggered preload structure with built-in spring sheet as described in claim 9, characterized in that: The groove is an arc-shaped groove or a conical groove; the first tip and the second tip are conical and make point contact with the groove.

11. The roller screw bidirectional staggered preload structure with built-in spring sheet as described in claim 8, characterized in that: Each spring clip is provided with a bearing or a washer between itself and the fastener.

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