TWM676481U - Built-in spring roller screw bidirectional staggered preload structure - Google Patents

Abstract

A bidirectional staggered preload structure for a roller screw with a built-in spring includes a screw, a nut, a roller assembly, two preload retention units, and a fastener assembly. The outer circumferential surface of the screw has a threaded structure, the nut is fitted onto the screw, and the inner circumferential surface has an annular groove section and two limiting grooves. The roller assembly is disposed between the screw and the nut, and includes a first roller and a second roller arranged in a staggered pattern. Each roller has annular teeth on its outer circumference, which respectively mesh with the threaded structure and the annular groove section. Two retaining preload units are respectively disposed at two opposite ends of the roller assembly. Each retaining preload unit includes a retainer and a spring plate. The two retainers each have a plurality of retaining holes for accommodating the positioning ends of each roller. The spring plate forms a plurality of elastic upturned feet that tilt and rise towards the roller assembly in the circumferential direction, and is radially offset relative to the retaining holes. A gap is formed between the positioning end of each roller and the bottom of the corresponding retaining hole, and the tip abuts against the elastic upturned foot on the opposite side and causes it to deform elastically. Through this gap and abutting relationship, axial preload in opposite directions can be applied to the first roller and the second roller respectively, forming a bidirectional staggered preload effect, thereby compensating for the gap, improving transmission accuracy and motion stability.

Description

Built-in spring roller screw bidirectional staggered preload structure

This invention 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.

Planetary roller screw transmission assemblies (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 arranged between a screw and a nut, surrounding the screw's outer circumference. Through the rolling engagement of the rollers between the screw and nut, rotational motion is converted into linear movement, thereby driving external loads.

As shown in Figure 1A, a typical planetary roller screw transmission device 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 rollers 13, and an annular tooth structure 12t is provided on the inner circumference of the nut 12 for engaging 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 rollers 13 to position the rollers 13 between the screw 11 and the nut 12 and to maintain their circumferential spacing.

However, in actual operation, the aforementioned traditional device still has several problems. As shown in Figures 1B and 1C, firstly, the geometric fit between the 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 the roller 13 and the screw 11/nut 12, causing the actual contact position of the roller 13 to deviate from the designed pitch circle radius. If this gap G is not effectively compensated, the roller 13 and nut 12 lack sufficient friction during operation, resulting in slippage or freewheeling, making it difficult to maintain pure rolling contact and causing sliding friction. Consequently, the roller 13 experiences greater wear, reducing the overall structural life. Similarly, insufficient contact may cause slippage between the roller 13 and the screw 11, thereby disrupting the deceleration and propulsion effect of the planetary motion and causing a decrease in linear propulsion efficiency and positioning accuracy.

In addition, 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. It also fails to effectively improve the sliding offset problem of the roller 13 caused by the clearance G.

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

The purpose of this invention is to provide a bidirectional staggered preload structure for a roller screw with a built-in spring 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 staggered rollers to achieve a stable bidirectional rolling contact effect, thereby improving the overall transmission efficiency, reducing wear, and extending service life.

To achieve the above objectives, this invention provides a bidirectional staggered preload structure for a roller screw with a built-in spring, comprising: a screw, a nut, a roller assembly, two retaining preload units, and a fastener assembly. The outer circumferential surface of the screw is provided with a threaded structure, the nut is sleeved on the screw, and the inner circumferential surface is provided with at least one annular groove section and two limiting grooves.

The roller assembly is positioned between a screw and a nut, comprising a plurality of staggered first rollers and a plurality of second rollers. Each roller has annular teeth on its outer periphery, which respectively mesh with the thread structure of the screw and the annular groove section of the nut. Each first roller has a first locating end and a first tip at its opposite ends, and each second roller has a second locating end and a second tip at its opposite ends.

The two retaining preload units are respectively disposed at opposite 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 a first positioning end and a second positioning end. The spring plate forms a plurality of elastic upturned feet inclined toward the roller assembly in the circumferential direction, and the elastic upturned feet are radially offset relative to the retaining holes. The elastic upturned feet of the two spring plates elastically abut against the first tip and the second tip, respectively.

The fastener assembly has two fasteners, which are respectively disposed on the outer side of the two retainers and embedded in the limiting groove on the inner circumferential surface of the nut, so as to fix the two retaining preload units and axially limit them in the nut.

In the assembled state, a first gap is formed between the first positioning end and the bottom of the retaining hole of the retainer at one end, and the first tip abuts against the elastic upturned foot of the spring piece at the opposite end, causing the elastic upturned foot to undergo elastic deformation; a second gap is formed between the second positioning end and the bottom of the retaining hole of the retainer at the opposite end, and the second tip abuts against the elastic upturned foot of the spring piece at one end, causing it to also undergo elastic deformation.

By leveraging the elastic deformation generated by the elastic upturn of the two end springs through the first and second tips respectively abutting against them, and in conjunction with the staggered arrangement of the first and second gaps, preload is transmitted from the first and second tips in opposite directions to the first and second rollers, applying axial preload in opposite directions. This creates a bidirectional staggered preload effect at both ends of the roller assembly, effectively eliminating backlash between the screw and nut, and maintaining pure rolling contact of the rollers in the thread structure and annular groove section.

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

In another embodiment, the aforementioned retaining preload unit can also omit the retainer and be directly composed of a spring with positioning holes and elastic upturned feet, thereby simultaneously achieving the dual functions of roller positioning and preload. The two retaining preload units are respectively located at opposite ends of the roller assembly, each including a spring with a plurality of positioning holes and a plurality of elastic upturned feet inclined toward the roller assembly. The positioning holes of the two springs respectively accommodate corresponding first positioning ends and second positioning ends, and the elastic upturned feet of the two springs are respectively abutted by corresponding first and second tips and produce elastic deformation.

By directly providing positioning functionality through the spring body of each preload retaining unit, the retainer structure can be omitted, thereby simplifying the component structure and reducing assembly time. The number of elastic upturned feet on each spring can correspond to the total number of the first and second rollers, and 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 inside the external opening to avoid contact between the first and second positioning ends and the gaskets or bearings on the outer side of the spring, and to form a functionally staggered first and second gap.

Through the above structural design, this new type of device can effectively compensate for the clearance caused by manufacturing and assembly errors, prevent the roller from slipping and deviating during movement, reduce friction, and improve motion accuracy. The staggered bidirectional preload structure simultaneously improves the stability and fit of the roller in both directions, further ensuring that the transmission system has excellent accuracy and reliability under high load and high dynamic motion conditions.

The structure and functional characteristics of this novel bidirectional staggered preload structure of a built-in spring roller screw will be explained with reference to the preferred embodiment of the accompanying drawings.

Please refer to Figures 2, 3A-3D, 4 and 5A to 5C. A preferred embodiment of the present invention has a bidirectional staggered preload structure with a built-in spring plate, comprising: a screw 21, a nut 22, a roller assembly R, two preload holding units K and a fastener assembly C.

The nut 22 may be a hollow cylindrical component with an inner hole 220 penetrating 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 annular groove sections 221 provide circumferential guidance and contact restraint, allowing the roller assembly R to roll stably within the nut 22 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 near the ungrooved area.

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.

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 the axis of the nut 22, and at least one end extends to the outside of the nut 22 for connecting to a drive device or mounting to other external mechanisms. The outer circumferential surface of the screw 21 is provided with a thread structure 211 (also called a helical groove or helical tooth), which can be in the form of 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 action between its thread structure 211 and the roller assembly R, the roller assembly R simultaneously generates planetary rolling motion of rotation and revolution between the screw 21 and the nut 22. 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 pushing effect.

Referring again to Figures 2, 3A-3C and 4, 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 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. 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.

The first roller 23 and the second roller 24 are each a cylindrical component extending along the axial direction, and are provided with a plurality of ring teeth 23t and 24t on their outer peripheral 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, 241 and at least one second engagement section 232, 242, wherein the diameter of the first engagement section 231, 241 is larger than the diameter of the second engagement section 232, 242. The annular teeth 23t and 24t of the first engagement sections 231 and 241 are used to roll and engage with the thread structure 211 of the screw 21, while the annular teeth 23t and 24t of the second engagement sections 232 and 242 are used to roll and engage with the annular groove 221g of the annular groove section 221 of the nut 22.

As shown in Figures 3A and 4, 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 a second engagement section 232 and 242 are respectively provided at both ends, so as to form a double-sided rolling engagement relationship with the screw 21 and the nut 22. Furthermore, in order to avoid interference between the first engagement sections 231 and 241 and the inner wall of the nut 22, the 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.

Each first roller 23 has a first positioning end 233 and a first tip 234 formed at opposite ends, and each second roller 24 has a second positioning end 243 and a second tip 244 formed at 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 tapered (conical).

Referring again to Figures 2, 3A, 3D, 4, 5A, 5B, and 5C, the preload units K are respectively disposed at opposite ends of the roller assembly R. Each preload unit K includes a retainer 26 and a spring piece 27. Each retainer 26 is provided with a plurality of retaining holes 261 and a plurality of fitting grooves 262. The 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, thereby stabilizing the angular spacing of the first and second rollers 23 and 24 in the circumferential direction. The fitting grooves 262 are provided on the periphery of the retainer 26. Each spring 27 (e.g., annular spring) is disposed between the inner side of the retainer 26 and the roller assembly R, forming a plurality of elastic upturned feet 271 inclined toward the roller assembly R in the circumferential direction (e.g., the inner edge circumferential direction). These 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 each corresponding to three elastic upturned feet 271), and are arranged circumferentially to ensure that each first roller 23 and second roller 24 is uniformly preloaded. The elastic upturned foot 271 is in an uncompressed upturned state before assembly and is radially offset relative to the retaining hole 261. This uncompressed upturned state helps provide effective elastic preload after assembly, ensuring uniform force on each of the first rollers 23 and the second rollers 24 and enhancing stability. The outer edge of the spring piece 27 is provided with a plurality of engaging feet 272, corresponding to the engaging grooves 262 of the retainer 26, for a detachable positioning assembly. Alternatively, the retainer 26 and the spring piece 27 can also be integrally formed.

Furthermore, each of the free ends of the elastic upturned feet 271 is provided with a groove 271r to allow the first tip 234 and the second tip 244 to abut against each other. The groove 271r can be an arc-shaped groove (as shown in Figure 5B) or a tapered groove (as shown in Figure 5C). The tapered first tip 234 and second tip 244 form a point contact relationship 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.

The fastener assembly C includes two fasteners 29 (e.g., C-shaped or O-shaped fasteners), which are respectively disposed on the outer side 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.

As shown in Figures 2, 3A, 4, 5A to 5C, 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 right-end retainer 26. The first tip 234 abuts against the elastic upturned foot 271 of the left-end spring piece 27, causing it to be compressed 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 left-end retainer 26. The second tip 244 abuts against the elastic upturned foot 271 of the right-end spring piece 27, also causing elastic deformation. By having the first tip 234 and the second tip 244 respectively abut against the spring pieces 27 at the left and right ends, the groove 271r of the elastic upturned foot 271 forms point contact with the first tip 234 and the second tip 244, generating elastic deformation. In addition, the first gap 31 and the second gap 32 are staggered at opposite ends of the roller assembly R, applying axial preload in opposite directions to the first roller 23 and the second roller 24, achieving a bidirectional staggered preload structure, and realizing selective control of the preload transmission direction.

As shown in Figures 6A and 6B, the preload applied by the elastic upturned foot 271 of the spring piece 27 at the left end in Figure 5A 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 thread structure 211 of the screw 21 and the left side of the annular groove 221g of the nut 22, creating a stable engagement and preventing slippage and freewheeling.

Similarly, as shown in Figures 7A and 7B, the preload generated by the elastic upturned foot 271 of the spring piece 27 at the right end in Figures 5A to 5C is directly transmitted to the second roller 24 through the second tip 244. This, combined with the second gap 32 between the roller and the retainer 26 at the left end, 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.

This design utilizes two preload retaining units K, each positioned at one end of the roller assembly R, to precisely guide the transmission path of the axial preload. This ensures that each elastic foot 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 respectively. 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 clearances 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.

Please continue referring to Figure 8. In this novel design, an additional bearing 33 (e.g., ball, roller, or needle bearing) can be provided 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, improving the dynamic stability of the transmission system.

Please refer to Figures 9A to 9D. In another preferred embodiment, the roller screw with built-in spring sheet has a bidirectional staggered preload structure. Its main structure is basically the same as the aforementioned embodiment, and the same components and connections will not be described again. The difference in this embodiment is that each retaining preload unit K located at both ends of the roller assembly R includes a spring sheet 27a (e.g., an annular spring sheet), omitting the retainer. The spring sheet 27a has a plurality of elastic upturned feet 271a and a plurality of positioning holes 273a that are inclined and raised towards the roller assembly R along its circumference (e.g., the inner circumferential direction). The structure of the elastic upturned foot 271a in this embodiment is the same as that of the elastic upturned foot 271 in the previous embodiment. The free end of the elastic upturned 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 upturned feet 271a is equal to the total number of the first roller 23 or the second roller 24 (e.g., three rollers each correspond to three elastic upturned feet 271a), and they are arranged circumferentially to ensure that each first roller 23 or each second roller 24 receives uniform preload. The elastic upturned foot 271a is radially offset relative to the positioning hole 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 assembly R. The positioning hole 273a respectively accommodates 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.

Each spring clip 27a has a positioning hole 273a forming an outer opening 2731a on the outer surface of the spring clip 27a. The first positioning end 233 and the second positioning end 243, which are 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.

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 upturned foot 271a and a positioning hole 273a, thereby simultaneously realizing 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 in the aforementioned embodiment, the bearing 33 can improve rotational smoothness and absorb vibration. If the bearing 33 is omitted, a washer (not shown) can be provided. This washer can be a ring-shaped 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 the preload effect from being affected by external forces. Meanwhile, the first and second positioning ends 233 and 243, which have an axial difference from the outer opening 2731a, do not contact the gasket.

In summary, the novel bidirectional staggered preload structure of the roller screw with built-in spring plates utilizes preload-holding units K arranged at both ends of the roller assembly R. Through the elastic upturned feet 271 and 271a of the spring plates 27 and 27a, and the staggered arrangement of the first clearance 31 and the second clearance 32, the first roller 23 and the second roller 24 are subjected to preload forces in opposite directions, thus establishing a staggered bidirectional force application mechanism. This structure not only effectively compensates for clearances caused by machining tolerances and eliminates initial backlash, but also stabilizes the motion trajectories of the first and second rollers 23 and 24, ensuring they always maintain a pure rolling state and effectively suppressing sliding friction and idling phenomena.

The above is a detailed description of the preferred embodiments of this invention. Any equivalent or similar modifications made in accordance with the teachings disclosed in this invention are naturally included within the scope of protection of this patent.

21: Screw 211: Thread structure 22: Nut 220: Inner hole 221: Annular groove section 221g: Annular groove 222: Limiting groove 223: Relief groove section R: Roller assembly 23: First roller 23t: Annular tooth 231: First engagement section 232: Second engagement section 233: First positioning end 234: First tip 24: Second roller 24t: Annular tooth 241: First engagement section 242: Second engagement section 243: Second positioning end 244: Second tip K: Retaining preload unit 26: Retainer 261: Retaining hole 262: Fitting groove 27, 27a: Spring piece 271, 271a: Flexible upturned feet; 271r, 271ra: Grooves; 272: Fitting feet; 273a: Locating holes; 2731a: External opening; C: Fastener assembly; 29: Fastener; 31: First clearance; 32: Second clearance; 33: Bearing.

Figure 1A is a structural schematic diagram of a conventional planetary roller screw transmission device; Figure 1B is a schematic diagram of the meshing contact relationship between the roller and the nut in Figure 1A; Figure 1C is a schematic diagram of the meshing contact relationship between the roller and the screw in Figure 1A; Figure 2 is a three-dimensional exploded schematic diagram of an embodiment of the present invention; Figure 3A is a combined sectional view of an embodiment of the present invention; Figure 3B is a partially enlarged schematic diagram of Figure 3A; Figure 3C is a right-side sectional view of Figure 3A; Figure 3D is a three-dimensional schematic diagram of a preload holding unit; Figure 4 is a schematic diagram of the first roller and the second roller in an embodiment of the present invention; Figure 5 Figure A is a schematic diagram of how the retaining preload members at both ends of the roller assembly generate axial preload in opposite directions for the first and second rollers in this embodiment of the invention; Figure 5B is an enlarged schematic diagram of the arc-shaped groove; Figure 5C is an enlarged schematic diagram of the conical groove; Figures 6A and 6B are schematic diagrams of the second roller being pushed to the right in this embodiment of the invention; Figures 7A and 7B are schematic diagrams of the first roller being pushed to the left in this embodiment of the invention; Figure 8 is a schematic diagram of selectively installing a bearing between the retaining preload unit and the fastener in this invention; Figures 9A to 9D are schematic diagrams of variations in the retaining preload unit of this invention.

21: Screw

211: Threaded Structure

22: Nuts

220: Inner Hole

R: Roller assembly

23: First Rolling Column

24: Second Roller

K: Maintain preload unit

26: Retainer

27: Shrapnel

C: Fastener assembly

29: Fasteners

261: Retaining Hole

262: Fitting slot

271: Elastic Upturned Legs

272: Chimera

Claims (11)

A bidirectional staggered preload structure for a roller screw with a built-in spring includes: a screw with a threaded structure on its outer circumferential surface; a nut fitted onto the screw, with at least one annular groove section and two limiting grooves on its inner circumferential surface; and a roller assembly disposed between the screw and the nut, having a plurality of staggered first rollers and a plurality of second rollers, each of the first rollers having a first positioning end and a first tip at both ends, and each of the second rollers having a corresponding end to the first roller. The assembly includes a second positioning end and a second tip. Each roller has annular teeth on its outer periphery, which respectively mesh with the thread structure and the annular groove section. Two retaining preload units are disposed within the nut and located at opposite ends of the roller assembly. Each unit includes a retainer and a spring clip. 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 clip is disposed between the inner side of the retainer and the roller assembly, and forms a plurality of oriented spring clips circumferentially. The roller assembly has tilted, upturned elastic legs that are radially offset relative to the retaining holes. Each of the two elastic tabs elastically abuts against the first and second tips, respectively. A fastener assembly has two fasteners respectively disposed on the outer side of the two retaining preload units and embedded in the limiting groove, used to axially limit the two retaining preload units within the nut. The radial offset of the elastic upturned legs and the retaining holes causes the first and second tips to abut against the retaining holes. The elastic upturn of the two spring plates causes elastic deformation of the upturned ends, and forms a first gap and a second gap with the bottom of the corresponding retaining hole, respectively, so that the first tip and the second tip transmit preload in opposite directions, applying axial preload in opposite directions to the first roller and the second roller, thereby forming bidirectional staggered preload at both ends of the roller assembly, reducing the back clearance between the screw and the nut, and maintaining pure rolling contact of the rollers. As described in claim 1, the roller screw bidirectional staggered preload structure with built-in spring sheet, wherein the retainer is provided with a plurality of fitting grooves, the spring sheet is an annular spring sheet, and its outer edge is provided with a plurality of fitting feet, which are correspondingly inserted into the fitting grooves to achieve detachable positioning. The built-in spring plate of the roller screw bidirectional staggered preload structure as described in claim 1, wherein each of the multiple elastic upturned feet of the spring plate is provided with a groove, and the first tip and the second tip respectively correspond to the groove. The built-in spring plate of the roller screw bidirectional staggered preload structure as described in claim 3, wherein the groove is an arc-shaped groove, a tapered groove, or a geometric groove; the first tip and the second tip are tapered and form point contact with the groove. The bidirectional staggered preload structure of the roller screw with built-in spring as described in claim 1, wherein the elastic upturned feet are arranged radially and are in an upturned state when not under force. The bidirectional staggered preload structure of the built-in spring roller screw as described in claim 1, wherein a bearing is provided between the preload holding unit and the fastener. The roller screw bidirectional interleaved preload structure with built-in spring as described in claim 1, wherein the retainer and the spring are integrally formed. A bidirectional staggered preload structure for a roller screw with a built-in spring includes: a screw with a threaded structure on its outer circumferential surface; a nut fitted onto the screw, and having at least one annular groove section and two limiting grooves on its inner circumferential surface; and a roller assembly disposed between the screw and the nut, having a plurality of staggered first rollers and a plurality of second rollers, each first roller having a first positioning end and a first tip at opposite ends, and each second roller having a first positioning end and a first tip at opposite ends. A second positioning end and a second tip are formed opposite to the two ends of the first roller. Each roller has annular teeth on its outer periphery, which respectively mesh with the thread structure and the annular groove section. Two retaining preload units are respectively disposed at opposite ends of the roller assembly, each including a spring plate. The spring plate has a plurality of positioning holes and a plurality of elastic upturned feet inclined towards the roller assembly. The positioning holes of the two spring plates respectively accommodate the first positioning end and the second positioning end. The spring plates... The elastic protrusions are radially offset relative to the positioning hole, and elastically abut against the corresponding first and second tips respectively; a fastener assembly has two fasteners, respectively disposed on the outer side of the two preload retaining units and embedded in the limiting groove, for fixing the two preload retaining units and axially limiting them within the nut; by means of the radially offset arrangement of the elastic protrusions and the positioning hole, the first and second tips respectively abut against the elastic protrusions of the two spring pieces. This causes the elastic upturned foot to undergo elastic deformation, thereby forming a first gap and a second gap between the first positioning end and the corresponding positioning hole of the second positioning end, respectively. This allows the first tip and the second tip to 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. The built-in spring roller screw bidirectional staggered preload structure as described in claim 8, wherein the elastic upturned foot has a groove at a free end, the groove forming point contact with the corresponding first tip or second tip. The built-in spring plate of the roller screw bidirectional staggered preload structure as described in claim 9, wherein the groove is an arc-shaped groove, a tapered groove, or a geometric groove; the first tip and the second tip are tapered and form point contact with the groove. The built-in spring clip roller screw bidirectional staggered preload structure as described in claim 8, wherein a bearing or a washer is provided between each spring clip and the fastener.