Retainer and circulating type planetary roller lead screw pair

Abstract

The invention relates to the technical field of high-precision transmission, and particularly discloses a retainer and a circulating type planetary roller lead screw pair. Wherein the retainer comprises a circular ring-shaped main body, a plurality of pin roller guide grooves which are uniformly distributed in the circumferential direction are formed in the circular ring-shaped main body, the pin roller guide grooves extend in the radial direction of the circular ring-shaped main body, and openings penetrating to an inner hole in the circular ring-shaped main body are formed in the radial inner ends of the pin roller guide grooves; the two sides of the opening are shrunk inwards to form shrunk openings, and the shrunk openings are elastic. According to the structure, the retainer is in the shape of the circular ring and is arranged on the side face of the internal thread section of the nut, so that the overall radial size of the circulating type planetary roller screw pair can be reduced, and a reliable structural foundation is provided for achieving miniaturization and microminiaturization of the circulating type planetary roller screw pair; the roller guide grooves are provided with the openings, the radial size of the retainer can be made smaller, and therefore the overall radial size of the circulating type planetary roller lead screw pair is made smaller.

Description

Technical Field

[0001] The present invention relates to the field of high-precision transmission technology, and particularly relates to a cage and a circulating planetary roller screw pair. Background Art

[0002] Circulating planetary roller screw pairs are widely used in high-performance transmission scenarios such as robots, spacecraft, and precision machine tools to achieve large-load and high-precision linear motion. Its core principle is that multiple rollers circulate and roll in the thread channels between the screw and the nut, thereby achieving the effects of high transmission efficiency, high rigidity, and backlash-free transmission.

[0003] During the process of the roller rolling in the thread channel, an axial relative displacement is generated due to the inconsistency between its helix angle and that of the nut. Whenever the roller makes one revolution around the screw, the roller needs to axially move one lead relative to the screw. To achieve circular motion, when the roller runs to the notch area of the nut, the end cams arranged at both ends of the nut apply an axial thrust to the roller. Under this action, the roller lifts along the tooth profile angle direction, thereby bypassing the large diameter section of the screw and completing the stroke reset, and then re-entering the thread channel to continue running. In the above process, the cage plays a key guiding and positioning role. On the one hand, the cage ensures that each roller is in the accurate position, preventing interference or dislocation; on the other hand, the cage maintains appropriate contact with the roller, which helps to guide the roller to smoothly complete the process of disengaging from and returning to the thread track.

[0004] For traditional circulating planetary roller screw pairs, refer to the industry standard with the standard number "T / TCMCA 0026 - 2023" and the standard name "Planetary Roller Screw Pair". Among them, the cage is a squirrel-cage type cage, located between the screw and the roller, and is divided into three sections as a whole: the middle support section and the clearance sections on both sides. Among them, the support section needs to have sufficient thickness to guide the roller to smoothly disengage from and re-enter the thread channel; while the clearance section must be extremely thin to avoid interference with the end cam during the commutation process. This structure with extremely high requirements for thickness zoning is difficult to process in miniature screw pairs. Especially when the overall size is limited, the rigidity of the support section is difficult to guarantee, and the clearance section is prone to deformation, severely limiting the overall durability and structural reliability.

[0005] However, in some existing application scenarios, especially in the field of robots, the demand for miniaturization and micro-miniaturization of circulating planetary roller screw pairs is gradually increasing, while the squirrel-cage type cage in traditional circulating planetary roller screw pairs restricts the development of miniaturization and micro-miniaturization of circulating planetary roller screw pairs.

[0006] In addition, in traditional circulating planetary roller screw pairs, an end face cam is relied on to apply an axial force to the rollers, forcing the rollers to lift along the thread flank angle and realizing their separation from and re-entry into the threads. Although this structure achieves the synchronous linkage between the screw and the nut, since the rollers need to forcibly cross the thread crest during commutation, their violent contact with the metal surface will cause severe friction between the rollers and the thread crest, resulting in significant noise and thread wear problems.

[0007] Chinese invention patent with publication number CN116697013A discloses a circulating planetary roller screw, which changes the traditional cage-type cage structure. Among them, two cages are provided and are oppositely arranged at both ends in the nut, and a plurality of special-shaped through grooves for accommodating the radial displacement of the rollers are provided on the cage. It also includes a fixing ring and a guiding key. The fixing ring includes an annular base body, a roller radial driving boss and an inner groove, and the guiding key includes an installation base body, multiple groups of parallel special-shaped grooves, a cage mating surface, and a positioning pin installation hole.

[0008] For the circulating planetary roller screw disclosed in the above patent, the fixing ring, the guiding key and the cage work together to achieve the all-round constraint combination of the radial, axial and tangential movement trajectories during the roller circulation process, and have the advantage of relatively small internal impact load.

[0009] For the circulating planetary roller screw disclosed in the above patent, although the structure of the cage is simpler than that of the cage-type cage, however, special-shaped through grooves are punched on the ring, and the special-shaped through grooves do not penetrate the inner side of the cage. To avoid interference with the major diameter of the screw and the cam, its inner wall must be extremely thin, so it is still difficult to meet the miniaturization requirements. In addition, this structure relies on an additional roller radial driving boss provided on the fixing ring to achieve roller lifting during the commutation process. Although the noise is reduced to a certain extent, the structural complexity is increased, and it is still not conducive to the popularization and application of miniaturized production. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide a cage and a circulating roller screw pair that are conducive to miniaturization, so as to solve the technical defect that it is difficult to achieve miniaturization in the existing circulating roller screw pair.

[0011] To solve the above technical problem, the technical solution provided by the present invention is as follows: A cage is applied to a circulating planetary roller screw pair. The cage includes a circular ring-shaped main body. The circular ring-shaped main body is provided with an inner hole for accommodating the screw to pass through. A plurality of roller guiding grooves are evenly arranged along the circumferential direction on the circular ring-shaped main body. The roller guiding grooves extend along the radial direction of the circular ring-shaped main body. The radial inner end of the roller guiding groove is provided with an opening that penetrates to the inner hole on the circular ring-shaped main body. Both sides of the opening contract inward to form a constriction opening, and the constriction opening has elasticity.

[0012] A preferred embodiment, the material of the annular body is elastic, and the shrinkage opening is elastic based on the material of the annular body.

[0013] A preferred embodiment, a hollow groove penetrating through the inner hole of the annular body is provided between adjacent roller guide grooves, elastic arms are formed on both sides of the hollow groove, and the elastic arms on both sides of the roller guide groove form an elastic shrinkage opening.

[0014] A preferred embodiment, elastic arms protruding from the inner wall surface of the inner hole of the annular body are provided on both sides of the roller guide groove, and a shrinkage opening is formed between adjacent elastic arms.

[0015] A preferred embodiment, an inner arc portion for contact and cooperation with the roller is provided on the inner side of the shrinkage opening.

[0016] The present invention also discloses a circulating planetary roller screw pair, at least including: A screw, an external thread is provided on the screw; A nut, an internal thread section and mounting sections located on both sides of the internal thread section are provided in the nut, and an avoidance groove axially extending and penetrating through the internal thread section is provided on the inner wall of the nut; A cage, the cage adopts the cage according to any one of claims 1-5, and the cage is installed at a position close to the internal thread section on the mounting section in the nut; Rollers, a plurality of rollers are arranged between the screw and the nut, and both ends of the rollers are located in the roller guide grooves of the cage; when the rollers are in a mating state with the internal thread of the nut, the rollers are elastically clamped by the shrinkage openings of the roller guide grooves and drive the shrinkage openings to elastically deform outwards, and when the rollers run to the position of the avoidance groove, the elastic reset of the shrinkage openings drives the rollers to radially enter the avoidance groove; An end face cam, the end face cam is arranged on the outer side of the cage.

[0017] A preferred embodiment, cages are provided on both sides of the internal thread section.

[0018] A preferred embodiment, the roller includes a threaded section and smooth sections located at both ends of the threaded section, and the smooth sections of the roller are matched with the roller guide grooves; or, the roller only includes a threaded section, and both ends of the threaded section are matched with the roller guide grooves.

[0019] A preferred embodiment, a radial cut-off opening is provided on the cage.

[0020] A preferred embodiment, a card slot for accommodating the cage is provided in the nut.

[0021] The cage and the circulating planetary roller screw pair of this embodiment have the following beneficial effects compared with the prior art: (1) The cage is circular and is arranged on the side of the internal thread section of the nut, changing the structural form of the squirrel-cage type cage located between the rollers and the screw. In this way, the overall radial dimension of the circulating planetary roller screw pair can be reduced, providing a reliable structural basis for the miniaturization and micro-miniaturization of the circulating planetary roller screw pair.

[0022] (2) The roller guide groove on the cage is provided with an opening that penetrates through the inner hole on the circular main body. Compared with the structural form of the special-shaped through groove on the cage in CN116697013A without an opening, the radial dimension of the cage can be made smaller, and further the overall radial dimension of the circulating planetary roller screw pair can be made smaller, enabling the circulating planetary roller screw pair to be more miniaturized and micro-miniaturized.

[0023] (3) The opening of the roller guide groove on the cage is set as an elastic shrinkage opening. When the roller runs to the position of the avoidance groove and needs to be axially reset, the elastic reset of the shrinkage opening drives the roller to enter the avoidance groove radially. When crossing the top of the external thread of the screw, it drives the roller to reset, making the roller reset more smoothly, effectively reducing the friction between the roller and the external thread of the screw, effectively avoiding impact noise, and prolonging the service life of the screw and the roller.

[0024] (4) Compared with the structural form in CN116697013A where the radial displacement of the roller is realized by the combined action of the roller radial driving boss on the fixed ring and the special-shaped through groove on the cage, the elastic shrinkage opening is innovatively used to realize the radial displacement of the roller, with a simpler structure, lower cost, and more conducive to the miniaturization and micro-miniaturization development of the circulating planetary roller screw pair.

[0025] (5) The planar cage structure is convenient for machining methods such as CNC turning, milling, or stamping, replacing the traditional squirrel-cage type cage structure, greatly simplifying the production process, with higher production efficiency and lower cost.

[0026] (6) The cage design has excellent guiding characteristics, the roller runs more stably, and the system has stronger dynamic response. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a planar schematic diagram of the cage in the circulating planetary roller screw pair shown in the first embodiment; Figure 2 For Figure 1 the three-dimensional structural schematic diagram of the shown cage; Figure 3 It is an exploded state structural schematic diagram of the circulating planetary roller screw pair shown in the first embodiment; Figure 4Schematic diagram of the longitudinal sectional view of the structure of the circulating planetary roller screw pair shown in the first embodiment; Figure 5 Schematic diagram of the structure of the nut in the circulating planetary roller screw pair shown in the first embodiment; Figure 6 Schematic diagram of the transverse sectional view of the structure of the circulating planetary roller screw pair shown in the first embodiment; Figure 7 Planar schematic diagram of another embodiment of the cage in the circulating planetary roller screw pair shown in the first embodiment; Figure 8 Planar schematic diagram of another embodiment of the cage in the circulating planetary roller screw pair shown in the first embodiment; Figure 9 Planar schematic diagram of the cage in the circulating planetary roller screw pair shown in the second embodiment; Figure 10 Schematic diagram of the longitudinal sectional view of the structure of the circulating planetary roller screw pair shown in the second embodiment. Detailed implementation manners

[0028] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "upper", "lower", "front", "rear", "inner", "outer", etc. are based on the orientation or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0030] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it may be a fixed connection, an integral connection, or a detachable connection; it may be the communication inside two elements; it may be directly connected, or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0031] First embodiment, A kind of circulating planetary roller screw pair of this embodiment, as Figures 3 - 5As shown in the figure, it includes a lead screw 50, a nut 20, rollers 30, an end face cam 40 and a cage 10. Among them, an external thread is provided on the lead screw 50, and an internal thread section 21 and mounting sections 22 located on both sides of the internal thread section are provided inside the nut 20. The mounting sections 22 are used to mount the cage 10 and the end face cam 40. An avoidance groove 23 extending axially and passing through the internal thread section 21 is provided on the inner wall of the nut 20. The rollers 30 are axially reset based on the convex portion 41 on the end face cam 40 at the position where the avoidance groove 23 is located. It should be noted that the above structures are all mature structures of the cyclic planetary roller screw pair in the art, and their specific structures will not be elaborated in this embodiment.

[0032] As a special feature of this embodiment, the cage 10 in this embodiment is as Figures 1 - 2 shown, including an annular main body 11, and the annular main body 11 has an inner hole 12 for accommodating the lead screw to pass through. Among them, a plurality of roller guide grooves 13 evenly distributed in the circumferential direction are provided on the annular main body 11, and the roller guide grooves 13 extend in the radial direction of the annular main body 11. The rollers 30 can achieve radial displacement in the roller guide grooves 13.

[0033] In this embodiment, an opening penetrating through to the inner hole 12 on the annular main body 11 is provided at the radially inner end of the roller guide groove 13, and both sides of the opening contract inward to form a constriction 16. Among them, the constriction 16 has elasticity.

[0034] In this embodiment, as Figure 6 shown, when the roller 30 is in a mating state with the internal thread of the nut 20, the roller 30 is elastically clamped by the constriction 16 of the roller guide groove 13 and drives the constriction to elastically deform outward. When the roller 30 runs to the position where the avoidance groove 23 is located, as Figure 6 shown at point A in the figure, the elasticity of the constriction 16 drives the roller 30 to enter the avoidance groove 23 radially. In this state, under the action of the convex portion 41 on the end face cam 40, the roller is axially reset. During the axial reset process of the roller, since the roller crosses the crest of the external thread of the lead screw, the reset of the roller is smoother, effectively reducing the friction between the roller and the external thread on the lead screw, effectively avoiding impact noise, and prolonging the service life of the lead screw and the roller.

[0035] In this embodiment, the roller 30 includes a threaded section 31 and smooth sections 32 located at both ends of the threaded section. The smooth sections 32 of the roller 30 cooperate with the roller guide grooves 13. Of course, this is only the preferred implementation mode of this embodiment. As an equivalent implementation mode of this embodiment, the roller may only include a threaded section without a smooth section, and both ends of the threaded section cooperate with the roller guide grooves 13.

[0036] Preferably, in this embodiment, an inner arc portion 18 for contacting and cooperating with the roller is provided on the inner side of the constriction opening 16, so that the constriction opening 16 has better wrapping property for the roller 30, and the driving of the radial displacement of the roller is smoother.

[0037] In this embodiment, as Figure 1 , Figure 2 shown, a hollow groove 17 penetrating through the inner hole 12 of the circular ring-shaped main body is provided between the adjacent roller guide grooves 13 on the cage 10, and elastic arms 15 are formed on both sides of the hollow groove 17. Among them, the hollow groove 17 plays a dual role of weight reduction and increasing the elasticity of the elastic arms.

[0038] Of course, it should be understood that forming the elastic arms through the hollow groove 17 and forming the elastic constriction opening by the elastic arms on both sides of the roller guide groove are only the preferred embodiments of this embodiment. Among them, the elastic constriction opening 16 can also be realized by other structural forms. For example, Figure 7 shown in the embodiment, the material of the circular ring-shaped main body has elasticity, and the constriction opening has elasticity based on the material of the circular ring-shaped main body; for another example, Figure 8 shown in the embodiment, elastic arms 15 protruding from the inner wall surface of the inner hole 12 of the circular ring-shaped main body are provided on both sides of the roller guide groove 13, and a constriction opening 16 is formed between the adjacent elastic arms.

[0039] In this embodiment, the material of the cage can be selected from different materials such as metal, engineering plastic, resin, etc. to adapt to diverse application scenarios.

[0040] In this embodiment, since the cage is of a planar structure, it is convenient for numerical control turning, milling or stamping processing, replacing the traditional squirrel-cage cage structure, greatly simplifying the production process, having higher production efficiency and lower cost.

[0041] In this embodiment, a pair of cages 10 are provided and are oppositely arranged on both sides of the internal thread section 21, and the end face cam is arranged on the outer side of the cage. It should be noted that this is only the preferred embodiment of this embodiment. In actual application, the position of the cage is not limited to both ends, and it can also be arranged on one side or in the middle of the double-nut structure.

[0042] Embodiment 2, A circulating planetary roller screw pair according to this embodiment, as Figure 9 , Figure 10 shown, is different from Embodiment 1 in that a radial cut-off opening 19 is provided on the cage 10, so that the cage 10 has the ability of elastic deformation. Correspondingly, as Figure 10 shown, a clamping groove 24 for accommodating the cage 10 is provided in the nut 20.

[0043] It should be noted that in this embodiment,Figure 9 The cage shown is based on Figure 1 、 Figure 2 The cage shown is provided with a radial cut 19. It should be understood that Figure 7 、 Figure 8 the cage shown can also be provided with a radial cut 19.

[0044] During assembly, based on the design of the radial cut 19, first compress the cage 10 radially, then place it in the card slot 24. After release, based on the elastic restoring force, the cage is installed in the card slot 24. This structure realizes the reliable fixation and safe operation of the cage in a small space. Its advantages are that the movement range of the cage in the axial direction is limited within the annular groove, avoiding axial drift or accidental detachment of the cage during operation; ensuring that the cage is always located in the working area corresponding to the rollers, ensuring the continuity of the roller circulation guidance; reducing the direct contact risk between the cage and structures such as end face cams, improving the fault tolerance of the system structure; optimizing the assembly process, making the installation of the cage faster, more accurate, and improving the maintenance convenience.

[0045] In conclusion, the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A cage, which is applied to a circulating planetary roller screw pair, is characterized in that, The cage includes an annular main body. The annular main body is provided with an inner hole for accommodating a lead screw to pass through. The annular main body is provided with a plurality of roller guide grooves evenly distributed in the circumferential direction. The roller guide grooves extend in the radial direction of the annular main body. The radial inner end of the roller guide groove is provided with an opening penetrating through to the inner hole of the annular main body. Both sides of the opening contract inward to form a constriction opening, and the constriction opening has elasticity.

2. The cage according to claim 1, characterized in that, The material of the annular main body has elasticity, and the constriction opening has elasticity based on the material of the annular main body.

3. The cage according to claim 1, characterized in that, A hollowed-out groove penetrating through to the inner hole of the annular main body is provided between adjacent roller guide grooves. Elastic arms are formed on both sides of the hollowed-out groove, and the elastic arms on both sides of the roller guide groove form an elastic constriction opening.

4. The cage according to claim 1, characterized in that, Elastic arms protruding from the inner wall surface of the inner hole of the annular main body are provided on both sides of the roller guide groove, and a constriction opening is formed between adjacent elastic arms.

5. The cage according to any one of claims 1-4, characterized in that, An inner arc portion for contact and cooperation with the roller is provided on the inner side of the constriction opening.

6. A cyclic planetary roller screw pair, characterized in that At least includes: A lead screw, on which an external thread is provided; A nut, in which an internal thread section and mounting sections located on both sides of the internal thread section are provided. An avoidance groove extending axially and penetrating through the internal thread section is provided on the inner wall of the nut; A cage, which adopts the cage described in any one of claims 1-5. The cage is installed at a position close to the internal thread section on the mounting section inside the nut; Rollers, a plurality of rollers are arranged between the lead screw and the nut, and both ends of the rollers are located in the roller guide grooves of the cage. When the rollers are in a mating state with the internal thread of the nut, the rollers are elastically clamped by the constriction openings of the roller guide grooves and drive the constriction openings to elastically deform outward. When the rollers run to the position of the avoidance groove, the elastic reset of the constriction openings drives the rollers to enter the avoidance groove radially; An end face cam, which is arranged on the outer side of the cage.

7. The circulating planetary roller screw pair according to claim 6, characterized in that, The cages are provided on both sides of the internal thread section.

8. The circulating planetary roller screw pair according to claim 6, characterized in that, The roller includes a threaded section and smooth sections located at both ends of the threaded section. The smooth sections of the roller cooperate with the roller guide grooves; or, the roller only includes a threaded section, and both ends of the threaded section cooperate with the roller guide grooves.

9. The circulating planetary roller screw pair according to any one of claims 6-8, characterized in that, A radial cut-off opening is provided on the cage.

10. The circulating planetary roller screw pair according to claim 9, characterized in that, A card slot for accommodating the cage is provided inside the nut.

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