Retainer and circulating planetary roller screw pair

Abstract

The application relates to the field of high-precision transmission technology, and particularly discloses a retainer and a circulating planetary roller screw pair. The retainer comprises a circular ring body, a plurality of roller guide grooves are arranged on the circular ring body and are uniformly distributed in the circumferential direction, the roller guide grooves extend along the radial direction of the circular ring body, an opening penetrating through an inner hole of the circular ring body is arranged at the radial inner end of the roller guide groove, the two sides of the opening are inwardly contracted to form a contraction opening, and the contraction opening is elastic. In the above structure, the retainer is circular ring-shaped and is arranged on the side surface of the inner threaded section of the nut, so that the overall radial size of the circulating planetary roller screw pair can be reduced, and a reliable structural basis is provided for realizing the miniaturization and micro-miniaturization of the circulating planetary roller screw pair; the roller guide groove is provided with the opening, the radial size of the retainer can be made smaller, and the overall radial size of the circulating planetary roller screw pair is smaller.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high-precision transmission technology, in particular to a cage and a circulating planetary roller screw pair. BACKGROUND

[0002] The circulating planetary roller screw pair is widely used in robots, spacecraft and precision machine tools and other high-performance transmission scenarios to achieve large load, high precision linear motion. Its core principle is to achieve high transmission efficiency, high rigidity and gapless transmission by circulating the multiple rollers in the screw thread channel between the screw and the nut.

[0003] During the rolling of the rollers in the screw thread channel, the axial relative displacement is generated due to the inconsistency of the helix angle of the rollers and the nut. Each time the roller revolves one revolution, the roller needs to move axially relative to the screw by one lead. To achieve circulating motion, when the roller runs to the gap area of the nut, the end face cam arranged at both ends of the nut will exert an axial thrust on the roller, and under the action of the thrust, the roller will lift up along the angle direction of the tooth profile, thereby bypassing the large diameter section of the screw and completing the travel reset, and re-entering the screw thread channel to continue running. In the above process, the cage plays a key role in guiding and positioning. On the one hand, the cage ensures that each roller is in the correct position to prevent interference or stringing; on the other hand, the cage and the roller maintain appropriate contact, which helps to guide the roller to smoothly complete the process of leaving and returning to the screw thread track.

[0004] The traditional circulating planetary roller screw pair, see the industry standard with standard number "T / TCMCA 0026-2023" and 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: a middle support section and two side clearance sections. Among them, the support section needs to have sufficient thickness to guide the roller to smoothly leave and re-enter the screw thread channel; while the clearance section must be extremely thin to avoid interference with the end face cam during the reversing process. This structure with extremely high requirements for thickness partitioning is difficult to machine in a miniature screw pair, especially in the case of limited overall size, the rigidity of the support section is difficult to guarantee, and the clearance section is prone to deformation, and the overall durability and structural reliability are severely limited.

[0005] However, some existing application scenarios, especially in the field of robots, have gradually increased the demand for miniaturization and miniaturization of the circulating planetary roller screw pair, and the squirrel cage type cage in the traditional circulating planetary roller screw pair limits the miniaturization and miniaturization development of the circulating planetary roller screw pair.

[0006] Furthermore, in traditional recirculating planetary roller screw assemblies, an end-face cam applies axial force to the rollers, forcibly lifting them along the thread angle to achieve disengagement and re-entry from the thread. Although this structure achieves synchronous linkage between the screw and the nut, the rollers must be forced to cross the thread crest during reversal, and the intense contact between the rollers and the metal surface causes severe friction between the rollers and the thread crest, resulting in significant noise and thread wear problems.

[0007] Chinese invention patent CN116697013A discloses a circulating planetary roller screw, which changes the traditional squirrel-cage cage structure. The cage has two cages positioned opposite each other at both ends of a nut, and multiple irregularly shaped grooves are provided on the cages to accommodate the radial displacement of the rollers. It also includes a retaining ring and a guide key. The retaining ring includes an annular base, a roller radial drive boss, and an inner groove. The guide key includes a mounting base, multiple sets of parallel irregularly shaped grooves, a cage mating surface, and a locating pin mounting hole.

[0008] The aforementioned patent discloses a cyclic planetary roller screw in which the fixed ring, guide key, and cage work together to achieve comprehensive constraint on the radial, axial, and tangential motion trajectories during the roller cycle, and has the advantage of low internal impact load.

[0009] The aforementioned patent discloses a circulating planetary roller screw, which, while having a simpler cage structure than a squirrel-cage cage, features irregularly shaped through-grooves punched into the ring that do not penetrate the inner side of the cage. To avoid interference with the screw's major diameter and the cam, the inner wall must be extremely thin, thus still failing to meet miniaturization requirements. Furthermore, this structure relies on additional radial drive bosses on the fixed ring to lift the rollers during reversal, which, while reducing noise to some extent, increases structural complexity and remains detrimental to widespread application in 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 overcome the technical defect that the circulating roller screw pair is difficult to miniaturize in the prior art.

[0011] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a cage, applied to a cyclic planetary roller screw pair, the cage comprising an annular body, the annular body having an inner hole for accommodating the screw through which it passes, the annular body having a plurality of roller guide grooves evenly distributed along the circumferential direction, the roller guide grooves extending along the radial direction of the annular body, the radial inner end of the roller guide groove having an opening penetrating to the inner hole of the annular body, the two sides of the opening contracting inward to form a contraction opening, the contraction opening having elasticity.

[0012] In a preferred embodiment, the material of the annular body is elastic, and the constriction opening is based on the elasticity of the material of the annular body.

[0013] In a preferred embodiment, a perforated groove extending through to the inner hole of the annular body is provided between adjacent roller guide grooves, and elastic arms are formed on both sides of the perforated groove, forming elastic contraction openings on both sides of the roller guide groove.

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

[0015] In a preferred embodiment, the inner side of the contraction opening is provided with an inner arc-shaped portion for contacting and engaging with the roller.

[0016] The present invention also discloses a cyclic planetary roller screw pair, comprising at least:

[0017] A lead screw, wherein the lead screw is provided with an external thread;

[0018] The nut has an internal thread section and mounting sections located on both sides of the internal thread section. The inner wall of the nut has an axially extending clearance groove that penetrates the internal thread section.

[0019] The retainer is the retainer described in the above-described scheme, and the retainer is installed on the mounting section inside the nut near the internal thread section;

[0020] A plurality of rollers are disposed between a lead screw and a nut, with both ends of the rollers located in the roller guide grooves of the cage; when the rollers are in the internal thread engagement state with the nut, the rollers are elastically clamped by the contraction opening of the roller guide groove and driven to elastically deform outward from the contraction opening; when the rollers run to the clearance groove position, the elastic reset of the contraction opening drives the rollers to radially enter the clearance groove.

[0021] An end face cam is disposed on the outer side of the cage.

[0022] In a preferred embodiment, the retainer is provided on both sides of the internal thread section.

[0023] In a preferred embodiment, the roller includes a threaded section and smooth sections located at both ends of the threaded section, the smooth sections of the roller cooperating with the roller guide groove; or, the roller includes only the threaded section, the two ends of the threaded section cooperating with the roller guide groove.

[0024] In a preferred embodiment, the cage is provided with a radial cut-off notch.

[0025] In a preferred embodiment, the nut is provided with a slot for accommodating the cage.

[0026] The cage and recirculating planetary roller screw assembly of this embodiment have the following advantages compared with the prior art:

[0027] (1) The cage is circular and is located on the side of the internal thread section of the nut. This changes the structure of the cage between the roller and the screw, thus reducing the overall radial dimension of the cyclic planetary roller screw pair and providing a reliable structural basis for miniaturization and micro-miniaturization of the cyclic planetary roller screw pair.

[0028] (2) The roller guide groove on the cage is provided with an opening that extends through to the inner hole of the annular body. Compared with the structure of the irregular through groove on the cage in CN116697013A which is not provided with an opening, the radial dimension of the cage can be made smaller, which in turn makes the overall radial dimension of the circulating planetary roller screw pair smaller, and makes the circulating planetary roller screw pair more miniaturized and micro-sized.

[0029] (3) The opening of the roller guide groove on the retainer is set as an elastic contraction opening. When the roller needs to be axially reset when it runs to the position of the relief groove, the elastic reset of the contraction opening drives the roller to enter the relief groove radially. When it passes the crest of the external thread on the screw, it drives the roller to reset, making the roller reset smoother, effectively reducing the friction between the roller and the external thread on the screw, effectively avoiding impact noise, and extending the service life of the screw and roller.

[0030] (4) Compared with the structure in CN116697013A where the radial drive boss on the fixed ring and the irregular through groove on the cage work together to achieve radial displacement of the roller, the innovative use of the elastic contraction opening to achieve radial displacement of the roller makes the structure simpler, the cost lower, and more conducive to the miniaturization and micro-miniaturization of the cyclic planetary roller screw pair.

[0031] (5) The planar cage structure facilitates CNC milling or stamping and other processing methods, replacing the traditional squirrel cage structure, greatly simplifying the production process, resulting in higher production efficiency and lower cost.

[0032] (6) The cage design has excellent guiding characteristics, making the rollers run more stably and the system dynamic response stronger. Attached Figure Description

[0033] Figure 1 This is a plan view of the cage in the cyclic planetary roller screw pair shown in Embodiment 1;

[0034] Figure 2 for Figure 1 A three-dimensional structural diagram of the cage shown;

[0035] Figure 3 This is a schematic diagram of the exploded state structure of the cyclic planetary roller screw pair shown in Example 1.

[0036] Figure 4 This is a schematic diagram of the longitudinal section of the cyclic planetary roller screw pair shown in Example 1.

[0037] Figure 5 This is a schematic diagram of the nut structure in the cyclic planetary roller screw pair shown in Example 1;

[0038] Figure 6 This is a cross-sectional view of the cyclic planetary roller screw pair shown in Example 1.

[0039] Figure 7 This is a plan view of another embodiment of the cage in the cyclic planetary roller screw pair shown in Example 1;

[0040] Figure 8 This is a plan view of another embodiment of the cage in the cyclic planetary roller screw pair shown in Example 1;

[0041] Figure 9 This is a plan view of the cage in the cyclic planetary roller screw pair shown in Embodiment 2;

[0042] Figure 10 This is a schematic diagram of the longitudinal section of the cyclic planetary roller screw pair shown in Example 2. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the 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 merely illustrative and not intended to limit the invention.

[0044] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0045] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an integral connection, or a detachable connection; they can refer to the internal connection of two components; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Example 1

[0046] This embodiment describes a type of cyclic planetary roller screw pair, such as... Figures 3-5 As shown, the assembly includes a lead screw 50, a nut 20, a roller 30, an end face cam 40, and a cage 10. The lead screw 50 has external threads, and the nut 20 has an internal thread section 21 and mounting sections 22 located on both sides of the internal thread section. The mounting sections 22 are used to mount the cage 10 and the end face cam 40. The inner wall of the nut 20 has an axially extending clearance groove 23 that penetrates the internal thread section 21. The roller 30 achieves axial reset at the location of the clearance groove 23 based on the protrusion 41 on the end face cam 40. It should be noted that the above structures are mature structures of circulating planetary roller lead screw pairs in this field, and their specific structures will not be described in detail in this embodiment.

[0047] As a special feature of this embodiment, the retainer 10 in this embodiment is as follows: Figures 1-2 As shown, it includes an annular body 11, which has an inner hole 12 for accommodating a lead screw. The annular body 11 is provided with a plurality of roller guide grooves 13 evenly distributed along the circumference. The roller guide grooves 13 extend along the radial direction of the annular body 11, allowing the rollers 30 to achieve radial displacement within the roller guide grooves 13.

[0048] In this embodiment, the roller guide groove 13 has an opening at its radially inner end that extends through to the inner hole 12 of the annular body 11. The two sides of the opening contract inward to form a contraction opening 16. The contraction opening 16 is elastic.

[0049] In this embodiment, as Figure 6 As shown, when the roller 30 and nut 20 are in the internal thread engagement state, the roller 30 is elastically clamped by the contraction opening 16 of the roller guide groove 13 and driven to elastically deform outward. When the roller 30 runs to the position of the clearance groove 23, as... Figure 6As shown at point A, the elastic reset mechanism of the contraction port 16 drives the roller 30 radially into the clearance groove 23. In this state, the roller achieves axial reset under the action of the protrusion 41 on the end face cam 40. During the axial reset process, the roller passes over the crest of the lead screw's external thread, making the roller reset smoother, effectively reducing the friction between the roller and the lead screw's external thread, effectively avoiding impact noise, and extending the service life of the lead screw and roller.

[0050] 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 groove 13. Of course, this is only a preferred embodiment of this embodiment. As an equivalent embodiment, the roller may only include the threaded section without the smooth sections, and the two ends of the threaded section cooperate with the roller guide groove 13.

[0051] Preferably, in this embodiment, the inner side of the contraction opening 16 is provided with an inner arc-shaped portion 18 for contacting and engaging with the roller, so that the contraction opening 16 has better wrapping effect on the roller 30 and drives the roller to move radially more smoothly.

[0052] In this embodiment, as Figure 1 , Figure 2 As shown, a perforated groove 17 extending through to the inner hole 12 of the annular body is provided between adjacent roller guide grooves 13 on the cage 10, and elastic arms 15 are formed on both sides of the perforated groove 17. The perforated groove 17 serves the dual purpose of reducing weight and increasing the elasticity of the elastic arms.

[0053] Of course, it should be understood that the elastic arms formed by the hollowed-out groove 17, and the elastic arms on both sides of the roller guide groove forming elastic contraction openings, are merely preferred embodiments of this example. The elastic contraction openings 16 can also be implemented through other structural forms, for example, Figure 7 In the illustrated embodiment, the material of the annular body is elastic, and the contraction opening is based on the elasticity of the material of the annular body; for example, Figure 8 In the embodiment shown, elastic arms 15 protruding from the inner wall of the annular main body inner hole 12 are provided on both sides of the roller guide groove 13, and a contraction opening 16 is formed between adjacent elastic arms.

[0054] In this embodiment, the cage material can be selected from different materials such as metal, engineering plastics, and resin to adapt to diverse application scenarios.

[0055] In this embodiment, since the cage has a planar structure, it is easy to perform CNC milling or stamping processing, replacing the traditional squirrel cage structure, which greatly simplifies the production process, resulting in higher production efficiency and lower costs.

[0056] In this embodiment, a pair of retainers 10 are provided and are disposed opposite to each other on both sides of the internal thread section 21, and the end face cam is disposed on the outer side of the retainer. It should be noted that this is only a preferred embodiment of this embodiment. In practical applications, the position of the retainer is not limited to both ends, and it can also be disposed on one side or in the middle of a double nut structure. Example 2

[0057] This embodiment describes a type of cyclic planetary roller screw pair, such as... Figure 9 , Figure 10 As shown, the difference from Embodiment 1 is that the retainer 10 is provided with a radial cut-off 19, giving the retainer 10 elastic deformation capability. Accordingly, as Figure 10 As shown, the nut 20 has a slot 24 for accommodating the retainer 10.

[0058] 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-off notch 19. It should be understood that... Figure 7 , Figure 8 The cage shown can also be provided with a radial cut-off 19.

[0059] During assembly, based on the design of the radial cut-off opening 19, the cage 10 is first radially compressed and then placed in the slot 24. After release, the cage is installed in the slot 24 based on the elastic restoring force. This structure enables reliable fixation and safe operation of the cage in a small space. Its advantages are that the range of motion of the cage in the axial direction is limited within the annular groove, avoiding axial drift or accidental dislodgement of the cage during operation; ensuring that the cage is always located in the working area corresponding to the roller, ensuring the continuity of roller cyclic guidance; reducing the risk of direct contact between the cage and structures such as the end face cam, improving the structural fault tolerance of the system; and optimizing the assembly process, making cage installation faster and more accurate, and improving maintenance convenience.

[0060] In summary, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A cage, applied to a cyclic planetary roller screw assembly, characterized in that, The cage includes an annular body with an inner hole for accommodating the lead screw. The annular body has a plurality of roller guide grooves evenly distributed along the circumference. The roller guide grooves extend radially along the annular body. The inner radial end of the roller guide groove has an opening that penetrates into the inner hole of the annular body. The two sides of the opening contract inward to form a contraction opening, which is elastic. In the recirculating planetary roller screw pair, both ends of the roller are located in the roller guide groove of the cage; when the roller is in the internal thread engagement state with the nut, the roller is elastically clamped by the contraction opening of the roller guide groove and driven to elastically deform outward. When the roller runs to the clearance groove position, the roller is driven to enter the clearance groove radially based on the elastic reset of the contraction opening.

2. The cage according to claim 1, characterized in that, The material of the annular body is elastic, and the contraction opening is based on the elastic material of the annular body.

3. The cage according to claim 1, characterized in that, A perforated groove is provided between adjacent roller guide grooves, extending through to the inner hole of the annular body. Elastic arms are formed on both sides of the perforated groove, and the elastic arms on both sides of the roller guide groove form elastic contraction openings.

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

5. The cage according to any one of claims 1-4, characterized in that, The inner side of the contraction opening is provided with an inner arc-shaped portion for contacting and engaging with the roller.

6. A circulating planetary roller screw pair, characterized in that, At least including: A lead screw, wherein the lead screw is provided with an external thread; The nut has an internal thread section and mounting sections located on both sides of the internal thread section. The inner wall of the nut has an axially extending clearance groove that penetrates the internal thread section. A retainer, wherein the retainer is the retainer according to any one of claims 1-5, and the retainer is mounted on the mounting section within the nut near the internal thread section; Rollers, multiple rollers are arranged between the lead screw and the nut; An end face cam is disposed on the outer side of the cage.

7. The cyclic planetary roller screw assembly according to claim 6, characterized in that, The retainer is provided on both sides of the internal thread section.

8. The cyclic planetary roller screw assembly 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 cooperating with the roller guide groove; or, the roller only includes a threaded section, the two ends of the threaded section cooperating with the roller guide groove.

9. The cyclic planetary roller screw assembly according to any one of claims 6-8, characterized in that, The cage is provided with a radial cut-off.

10. The cyclic planetary roller screw assembly according to claim 9, characterized in that, The nut has a slot for accommodating the cage.

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