Reverse rotation speed reduction type circulating roller lead screw pair

Abstract

The invention relates to the technical field of high-precision transmission, in particular to a reverse rotation speed reduction type circulating roller lead screw pair which at least comprises a lead screw, a nut, rollers, a retainer and an end face cam, external threads are arranged on the lead screw, internal threads are arranged in the nut, and the internal threads and the external threads are opposite in rotation direction and identical in thread pitch. In a traditional circulating type planetary roller lead screw pair, internal threads of a nut and external threads of a lead screw are the same in screwing direction and thread pitch, and when the lead screw rotates by one circle, the relative axial displacement of the nut and the lead screw is P; according to the invention, through improvement, after the scheme that the internal thread and the external thread are opposite in rotation direction and the same in thread pitch is adopted, when the lead screw rotates by one circle, the relative axial displacement of the nut and the lead screw is smaller than P, under the condition that the thread pitch is the same, the speed reduction type displacement relation is achieved, the output lead is smaller, and small-lead output is obtained on the premise that the large thread pitch is kept; and the thread machining performance and the structural rigidity are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high-precision transmission technology, and particularly relates to a counter-rotating reduction type circulating roller screw pair. BACKGROUND

[0002] The circulating planetary roller screw pair is a mechanism for converting rotary motion into high-efficiency linear motion, and is widely used in high-performance transmission scenarios such as aerospace, industrial robots, and precision machine tools. The circulating planetary roller screw pair realizes high rigidity, high load capacity, and backlash-free transmission through the circulation of multiple rollers in the thread channels between the screw and the nut.

[0003] With the development of technology, there are special needs for miniaturization, miniaturization, and small lead output of the circulating planetary roller screw pair in some compact space application scenarios such as robot dexterous hands and micro actuators. However, the traditional circulating planetary roller screw pair has the following defects when facing the needs of miniaturization, miniaturization, and small lead output: (1) In the traditional circulating planetary roller screw pair, the thread rotation direction and thread pitch of the screw and the nut are the same, and the roller has no thread angle. Among them, the lead of the circulating planetary roller screw pair (the relative axial displacement of the nut and the screw when the screw rotates one revolution) is calculated as follows: The relative axial displacement of the roller and the screw ( ):

[0004] The relative axial displacement of the nut and the roller ( ):

[0005] The relative axial displacement of the nut and the screw ( ):

[0006] Among them: k is the transmission ratio, that is, the ratio of the diameters of the screw and the roller; P is the thread pitch of the screw and the nut.

[0007] As shown above, the lead of the traditional circulating planetary roller screw pair is equal to the thread pitch P of the screw and the nut. Therefore, in order to realize small lead output, only the thread pitch P of the screw and the nut can be reduced. However, the smaller the pitch P, the narrower the thread profile and the lower the thread height, which significantly increases the difficulty of processing, seriously restricting the development of small lead output, miniaturization, and miniaturization of the circulating planetary roller screw pair.

[0008] (2) For traditional recirculating planetary roller screw pairs, see the industry standard numbered "T / TCMCA 0026-2023" and named "Planetary Roller Screw Pairs." The cage is a squirrel cage, which also limits the miniaturization and micro-scaling of recirculating planetary roller screw pairs.

[0009] (3) In traditional recirculating planetary roller screw pairs, an end cam is used to apply axial force to the roller, forcibly lifting the roller along the tooth profile angle to achieve its disengagement and re-entry from the thread. Although this structure achieves synchronous linkage between the screw and the nut, the roller must be forced to cross the tooth top during reversing. The intense contact with the metal surface will cause severe friction between the roller and the thread tooth top, resulting in significant noise and thread wear problems.

[0010] (4) In the traditional circulating planetary roller screw pair, the end face cam and the nut are positioned by radial locating pins or screws. However, due to the demand for miniaturization and micro-manufacturing, radial locating pins or screws cannot be used for positioning due to the small diameter of the nut. Summary of the Invention

[0011] The technical problem to be solved by the present invention is to solve the technical defects in the prior art that the traditional circulating planetary roller screw pair is difficult to achieve small lead output, miniaturization and micro-miniaturization application scenarios.

[0012] In order to solve the above technical problems, the present invention provides the following technical solutions: a counter-rotating reduction type circulating roller screw pair, comprising at least: A lead screw having an external thread; A nut having an internal thread, and an inner wall of the nut having an avoidance groove extending axially and penetrating the internal thread; Rollers, the outer circumference of which is provided with a plurality of ring teeth, and the plurality of rollers are arranged between the external thread of the lead screw and the internal thread of the nut; A pair of retainers are arranged on opposite sides of the roller in the axial direction, and each retainer is provided with a roller guide groove for accommodating the radial displacement of the roller; End face cams, a pair of end face cams are respectively arranged on the outer sides of the retaining frame, and a guide protrusion is provided on the end surface of the end face cam facing the retaining frame; The internal thread and the external thread have opposite rotation directions and the same thread pitch; When the screw rotates one circle, the relative axial displacement between the nut and the screw is as follows: Relative axial displacement of roller and screw: ; Relative axial displacement of the nut and roller: ; The relative axial displacement of the nut and the screw rod: ; wherein k is the transmission ratio, i.e. the ratio of the screw rod diameter and the roller diameter; and P is the thread pitch of the screw rod and the nut.

[0013] In a preferred embodiment, the retainer comprises a circular ring body, which is provided with an inner hole for accommodating the screw rod, and a plurality of roller guide grooves are arranged on the circular ring body in the circumferential direction and extend in the radial direction of the circular ring body.

[0014] In a preferred embodiment, the radial inner end of the roller guide groove is provided with an opening that penetrates into the inner hole of the circular ring body, and the two sides of the opening are inwardly contracted to form a contraction opening, which has elasticity. When the roller is in the engaged state with the inner thread of the nut, the roller is elastically clamped by the contraction opening of the roller guide groove and drives the contraction opening to elastically deform outwardly. When the roller runs to the avoidance groove position, the roller is driven to enter the avoidance groove in the radial direction based on the elastic reset of the contraction opening.

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

[0016] In a preferred embodiment, the material of the circular ring body has elasticity, and the contraction opening has elasticity based on the material of the circular ring body; or, a hollow groove that penetrates into the inner hole of the circular ring body is arranged between adjacent roller guide grooves, and the two sides of the hollow groove form elastic arms, and the elastic arms on both sides of the roller guide groove form an elastic contraction opening; or, the two sides of the roller guide groove are provided with elastic arms that protrude from the inner wall surface of the inner hole of the circular ring body, and the contraction opening is formed between adjacent elastic arms.

[0017] In a preferred embodiment, the nut further comprises, from both sides of the inner thread, a retainer mounting section, an end face cam mounting section, and an end face limiting mounting section.

[0018] In a preferred embodiment, the end face limiting mounting section is provided with an inner thread, and further comprises a threaded end cover that is adaptively connected with the end face limiting mounting section.

[0019] In a preferred embodiment, the end face cam is provided with a circumferential limiting protrusion, and the inner wall of the nut is provided with a limiting groove that is adapted to the circumferential limiting protrusion.

[0020] In a preferred embodiment, a limiting stop ring is arranged between the retainer and the end face cam.

[0021] In a preferred embodiment, the limiting stop ring is a C-shaped snap ring.

[0022] Compared with the prior art, the counter-rotating reduction circulating roller screw pair of the present invention has the following beneficial effects: (1) In the traditional circulating planetary roller screw pair, the internal thread of the nut and the external thread of the screw have the same rotation direction and the same thread pitch. When the screw rotates one circle, the relative axial displacement of the nut and the screw is P. In the present invention, by improving the scheme of the internal thread and the external thread having opposite rotation directions and the same thread pitch, the relative axial displacement of the nut and the screw when the screw rotates one circle is ,<P, under the condition of the same thread pitch, a deceleration displacement relationship is achieved, the output lead is smaller, and a small lead output is obtained while maintaining a larger pitch, thereby improving the thread processing performance and structural rigidity.

[0023] (2) The retainer is annular and is arranged on both sides of the roller. The structure of the squirrel cage retainer located between the roller and the screw is changed. This can reduce the overall radial size of the circulating planetary roller screw pair and provide a reliable structural basis for the miniaturization and micro-miniaturization of the circulating planetary roller screw pair.

[0024] (3) The opening of the roller guide groove on the retaining frame is set as an elastic shrinkage opening. When the roller runs to the avoidance groove position and needs to be axially reset, the elastic reset of the shrinkage opening drives the roller to enter the avoidance groove radially, and drives the roller to reset when passing over the top of the external thread on the screw, 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.

[0025] (4) The circumferential positioning between the end face cam and the nut is achieved through the circumferential limiting protrusion and limiting groove. Compared with the traditional radial positioning pins or screws, it ensures the accuracy and repeatability of the installation angle of the end face cam and is more suitable for positioning in small-scale scenes.

[0026] (5) When subjected to axial loads, the conventional nut and screw generate torque on the roller in the same direction. However, in the present invention, since the nut and screw rotate in opposite directions, the torques on the roller cancel each other out, making the roller less likely to slip. In other words, this structure has a better self-locking effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the longitudinal cross-section of the counter-rotating reduction type circulating roller screw pair of this embodiment; Figure 2 Schematic diagram of the exploded state structure of the counter-rotating reduction type circulating roller screw pair of this embodiment; Figure 3 Schematic diagram of the cage structure of the first embodiment of the counter-rotating reduction type circulating roller screw pair in this embodiment; Figure 4 Schematic diagram of the cage structure of the second embodiment of the counter-rotating reduction recirculating roller screw pair in this embodiment; Figure 5 Schematic diagram of the cage structure of the third embodiment of the counter-rotating reduction recirculating roller screw pair in this embodiment; Figure 6 Schematic diagram of the retainer structure of the fourth embodiment of the counter-rotating reduction recirculating roller screw pair in this embodiment; Figure 7 for Figure 6 A schematic diagram of the three-dimensional structure of the retainer shown; Figure 8 Schematic diagram of the cage structure of the fifth embodiment of the counter-rotating reduction recirculating roller screw pair in this embodiment; Figure 9 Schematic diagram of the cross-sectional structure of the nut in the counter-rotating reduction type circulating roller screw pair of this embodiment; Figure 10 for Figure 9 Schematic diagram of the axial projection structure of the nut shown; Figure 11 for Figure 9 A schematic diagram of the three-dimensional structure of the nut shown; Figure 12 Schematic diagram of the cross-sectional structure of the counter-rotating reduction type circulating roller screw pair of this embodiment; Figure 13 Schematic diagram of the three-dimensional structure of the end face cam in the counter-rotating reduction type circulating roller screw pair of this embodiment; Figure 14 for Figure 13 Schematic diagram of the axial projection structure of the end face cam shown. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, 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 intended to limit the present invention.

[0029] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "back", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations 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 cannot be understood as a limitation on 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 can be a fixed connection, an integral connection, or a detachable connection; it can be the internal communication of two components; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] A counter-rotating reduction type circulating roller screw pair of this embodiment, such as Figure 1 、 Figure 2 As shown, it includes a screw 50, a nut 20, a roller 30, an end cam 40, a retaining frame 10 and a threaded end cover 60.

[0032] Among them, the screw 50 is provided with an external thread 51, the nut 20 is provided with an internal thread 21, and the roller 30 is provided with a plurality of ring teeth 31, which do not have a thread lead angle, and multiple rollers 30 are arranged between the external thread 51 of the screw 50 and the internal thread 21 of the nut 20.

[0033] Among them, such as Figure 9 、 Figure 10 As shown, an escape groove 22 extending axially and penetrating the internal thread 21 is provided on the inner wall of the nut 20 , and the roller 30 is axially reset based on the guide protrusion 41 on the end face cam 40 at the position of the escape groove 22 .

[0034] It should be noted that the above structures are all mature structures of circulating planetary roller screw pairs in the art, and their specific structures are not described in detail in this embodiment.

[0035] As a special feature of this embodiment, the internal thread 21 and the external thread 51 have opposite rotation directions and the same thread pitch. Based on this design, in this embodiment, when the screw 50 rotates one circle, the relative axial displacement of the nut 20 and the screw 50 is as follows: Relative axial displacement of roller and screw: ; Relative axial displacement of the nut and roller: ; Relative axial displacement between nut and screw: ; Among them, k is the transmission ratio, that is, the ratio of the middle diameter of the screw to the roller; P is the thread pitch of the screw and nut.

[0036] As described above, the counter-rotating reduction recirculating roller screw pair of this embodiment is improved by adopting a scheme in which the internal thread 21 and the external thread 51 have opposite rotation directions and the same thread pitch. When the screw 50 rotates one circle, the relative axial displacement of the nut 20 and the screw 50 is While the conventional circulating planetary roller screw pair adopts the same rotation direction and the same thread pitch of the internal thread 21 and the external thread 51, the relative axial displacement between the nut 20 and the screw 50 is P when the screw 50 rotates one circle, wherein, <P.

[0037] In summary, in the case of the same thread pitch, the counter-rotation deceleration type circulating roller screw pair of the present embodiment realizes the deceleration type displacement relationship, has a smaller output lead, obtains a small lead output under the premise of maintaining a large pitch, improves the thread processing performance and structural rigidity, and does not need to reduce the pitch to obtain a small lead, which is convenient for processing and suitable for micro-feeding occasions.

[0038] In the present embodiment, the diameter of the screw 50 is set to 3mm, the diameter of the roller is set to 1mm, and the diameter of the nut is set to 5mm. When the right-handed pitch of the screw is 1mm and the left-handed pitch of the nut is 1mm, the lead of the counter-rotation deceleration type circulating roller screw pair is right-handed 0.25mm.

[0039] For comparison, if the conventional circulating planetary roller screw pair is adopted, the diameter of the screw 50 is set to 3mm, the diameter of the roller is set to 1mm, and the diameter of the nut is set to 5mm. When the right-handed pitch of the screw is 1mm and the right-handed pitch of the nut is 1mm, the lead of the circulating planetary roller screw pair is right-handed 1mm. In the technical scheme of the present embodiment, the output lead is one fourth of that of the conventional circulating planetary roller screw pair in the case of the same thread parameters.

[0040] The counter-rotation deceleration type circulating roller screw pair of the present embodiment can flexibly match different speed / displacement requirements by reasonably selecting the transmission ratio parameters, and the deceleration characteristics are naturally built into the structure, which improves the integration of the transmission system.

[0041] As a special feature of the present embodiment, the retainer 10 in the present embodiment includes a circular ring-shaped body 11 having an inner hole 12, as shown in Figures 3-8 The circular ring-shaped body 11 is provided with a plurality of roller guide grooves 13 uniformly distributed in the circumferential direction, which extend in the radial direction of the circular ring-shaped body 11, and the roller 30 can realize radial displacement in the roller guide groove 13.

[0042] In the present embodiment, the roller 30 includes a ring tooth segment having ring teeth 31 and light segments 32 located at both ends of the ring tooth segment, and the light segments 32 of the roller 30 are matched with the roller guide grooves 13. Of course, this is only a preferred embodiment of the present embodiment, and as an equivalent embodiment of the present embodiment, the roller can only include a ring tooth segment without a light segment, and the two ends of the ring tooth segment are matched with the roller guide grooves 13.

[0043] The structure of the retainer 10 of the first preferred embodiment in the present embodiment is as shown inFigure 3 As shown, the roller guide groove 13 does not pass through to the inner hole 12.

[0044] The structure of the cage 10 of the second preferred embodiment in this embodiment is as shown in Figure 4 As shown, the radial inner end of the roller guide groove 13 is provided with an opening passing through to the inner hole 12 of the annular body 11. This embodiment is compared with the structure of the cage shown in Figure 3 As compared with the structure of the cage shown in, since the wall between the roller guide groove 13 and the inner hole 12 is reduced at least in the radial direction, the radial dimension of the cage can be made smaller, and thus the overall radial dimension of the circulating planetary roller screw pair can be made smaller, which can make the circulating planetary roller screw pair more miniaturized and micro-sized.

[0045] The structure of the cage 10 of the third preferred embodiment in this embodiment is as shown in Figure 5 As shown, on the basis of the structure of the cage shown in Figure 4 The two sides of the opening are inwardly contracted to form a contraction opening 16. Moreover, the contraction opening 16 has elasticity. In this embodiment, the material of the annular body has elasticity, and the contraction opening is based on the material of the annular body to have elasticity.

[0046] As shown in Figure 12 As shown, in the state of cooperation between the roller 30 and the internal thread of the nut 20, the roller 30 is elastically clamped by the contraction opening 16 of the roller guide groove 13 and is driven to elastically deform the contraction opening outwardly. When the roller 30 runs to the position of the avoidance groove 22, as shown in A of Figure 12 the elasticity of the contraction opening 16 drives the roller 30 to enter the avoidance groove 22 in the radial direction. In this state, under the action of the guiding convex part 41 on the end face cam 40, the roller is axially reset. As compared with the cage shown in Figures 3-4 In the process of axial resetting of the roller, since the roller passes over the tooth top of the external thread of the screw, the resetting of the roller is more smooth, the friction between the roller and the external thread of the screw is effectively reduced, the impact noise is effectively avoided, and the service life of the screw and the roller is prolonged.

[0047] As preferred, in this embodiment, the inner side of the contraction opening 16 is provided with an inner arc-shaped part 18 for contact cooperation with the roller, so that the contraction opening 16 has better wrapping of the roller 30 and the driving of the radial displacement of the roller is more smooth.

[0048] The structure of the cage 10 of the fourth preferred embodiment in this embodiment is as shown in Figures 6-7 As shown, on the basis of the structure of the cage shown in Figure 5Based on the structure of the cage shown, a hollow groove 17 is provided between adjacent roller guide grooves 13, extending through the inner hole 12 of the annular body. Elastic arms 15 are formed on either side of the hollow groove 17, and the elastic arms on either side of the roller guide groove 13 form elastic constrictions 16. The hollow groove 17 serves the dual purpose of reducing weight and increasing the elasticity of the elastic arms.

[0049] The structure of the retainer 10 in the fifth preferred embodiment of this embodiment is as follows Figure 8 As shown, elastic arms 15 protruding from the inner wall surface of the annular main body inner hole 12 are provided on both sides of the roller guide groove 13, and elastic contraction openings 16 are formed between adjacent elastic arms.

[0050] In this embodiment, the material of the retaining frame can be selected from different materials such as metal, engineering plastic, resin, etc. to adapt to various application scenarios.

[0051] In this embodiment, since the retainer is a planar structure, it is convenient for CNC turning, milling or stamping processing, replacing the traditional squirrel cage retainer structure, greatly simplifying the production process, and improving production efficiency and reducing costs.

[0052] In this embodiment, a pair of retainers 10 are provided, positioned opposite each other on either side of the roller, and the end cams are positioned on the outside of the retainers. It should be noted that this is merely a preferred embodiment of this embodiment; in actual applications, the retainers are not limited to being positioned at either end and can also be positioned on a single side or in the middle of a double nut structure.

[0053] In this embodiment, Figure 1 、 Figure 2 、 Figure 9 As shown, the nut 20 further includes a retainer mounting section 23, an end face cam mounting section 24 and an end face limit mounting section 25 which are sequentially distributed from the internal thread to both sides.

[0054] Preferably, in this embodiment, the end face limit mounting section 25 is provided with an internal thread and also includes a threaded end cap 60 adapted to be connected to the end face limit mounting section. The retainer 10 is mounted within the retainer mounting section 23, and the end face cam 40 is mounted within the end face cam mounting section 24. The threaded end cap 60 constrains the end face cam 40 and the retainer 10 within the nut. In this embodiment, the detachable threaded end cap 60 facilitates subsequent replacement of internal components such as the end face cam, roller, and retainer. This design not only simplifies the maintenance process but also improves the repeatable assembly of the structure, facilitating rapid on-site replacement and debugging, which is beneficial for its widespread use in industrial scenarios.

[0055] It should be noted that the threaded end cover 60 is used to limit the end face cam 40 and the retainer 10 in the nut, which is only a preferred embodiment of the present embodiment, and other feasible limiting ways can also be used to limit the end face cam 40 and the retainer 10 in the nut.

[0056] As preferred, in the present embodiment, as shown in Figure 1 、 Figure 2 , a limiting check ring 70 is arranged between the retainer 10 and the end face cam 40. As preferred, the limiting check ring 70 is a C-shaped snap ring, and is assembled.

[0057] In the present embodiment, the retainer, the roller, the end face cam, the C-shaped snap ring and the threaded end cover and other structural parts do not need complex positioning or adjustment during assembly, have good guiding characteristics and matching precision, and can realize efficient assembly process. The structure is clear in cooperation, which is convenient for batch rapid assembly by using automatic equipment, and significantly improves production efficiency and consistency; As a special feature of the present embodiment, as shown in Figure 13 、 Figure 14 , the end face cam is provided with a circumferential limiting protrusion 42, as shown in Figure 9 、 Figure 11 , the inner wall of the nut 20 is provided with a limiting groove 26 matched with the circumferential limiting protrusion 42.

[0058] In the present embodiment, the circumferential limiting protrusion and the limiting groove are used to realize circumferential positioning between the end face cam and the nut, compared with the traditional radial positioning pin or screw, which ensures the accuracy and repeatability of the installation angle of the end face cam, and is more suitable for positioning in small size scenes.

[0059] As preferred, in the present embodiment, the end face cam 40 is provided with a ring table 43 extending into the retainer mounting section 23, the guide protrusion 41 is arranged on the end face of the ring table 43, and the circumferential limiting protrusion 42 is arranged on the circumferential surface of the ring table 43. Correspondingly, the limiting groove 26 is arranged on the inner wall surface of the retainer mounting section 23.

[0060] In summary, the above only describes the preferred embodiments of the present application, and does not limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A counter-rotating reduction type circulating roller screw pair, comprising at least: A lead screw having an external thread; A nut having an internal thread, and an inner wall of the nut having an avoidance groove extending axially and penetrating the internal thread; Rollers, the outer circumference of which is provided with a plurality of ring teeth, and the plurality of rollers are arranged between the external thread of the lead screw and the internal thread of the nut; A pair of retainers are arranged on opposite sides of the roller in the axial direction, and each retainer is provided with a roller guide groove for accommodating the radial displacement of the roller; End face cams, a pair of end face cams are respectively arranged on the outer sides of the retaining frame, and a guide protrusion is provided on the end surface of the end face cam facing the retaining frame; The invention is characterized in that the internal thread and the external thread have opposite rotation directions and the same thread pitch; When the screw rotates one circle, the relative axial displacement between the nut and the screw is as follows: Relative axial displacement of roller and screw: ; Relative axial displacement between nut and roller: Relative axial displacement between nut and screw: ; Among them, k is the transmission ratio, that is, the ratio of the middle diameter of the screw to the roller; P is the thread pitch of the screw and nut.

2. The counter-rotating reduction recirculating roller screw pair according to claim 1, characterized in that: The retaining frame includes an annular body, which is provided with an inner hole for accommodating the screw to pass through, and a plurality of roller guide grooves are evenly distributed on the annular body along the circumferential direction, and the roller guide grooves extend along the radial direction of the annular body.

3. The counter-rotating reduction recirculating roller screw pair according to claim 2, characterized in that: The radial inner end of the roller guide groove is provided with an opening that penetrates to the inner hole of the annular main body, and the two sides of the opening shrink inwardly to form a shrinkage opening, and the shrinkage opening is elastic. When the roller is in a state of cooperation with the internal thread of the nut, the roller is elastically clamped by the shrinkage opening of the roller guide groove and the shrinkage opening is driven to elastically deform outward. When the roller runs to the avoidance groove position, the roller is driven to enter the avoidance groove radially based on the elastic reset of the shrinkage opening.

4. The counter-rotating reduction recirculating roller screw pair according to claim 3, characterized in that: An inner arc portion for contacting and cooperating with the roller is provided on the inner side of the contraction opening.

5. The counter-rotating reduction recirculating roller screw pair according to claim 4, characterized in that: The material of the annular body is elastic, and the shrinkage opening is based on the elasticity of the material of the annular body; Alternatively, a hollow groove penetrating 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 hollow groove, and the elastic arms on both sides of the roller guide groove form elastic contraction openings; Alternatively, 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 contraction openings are formed between adjacent elastic arms.

6. The counter-rotating reduction recirculating roller screw pair according to any one of claims 1 to 5, characterized in that: The nut further includes a retainer mounting section, an end face cam mounting section and an end face limit mounting section which are sequentially distributed from the internal thread to both sides.

7. The counter-rotating reduction recirculating roller screw pair according to claim 6, characterized in that: The end face limiting installation section is provided with an internal thread and also includes a threaded end cover adapted to be connected to the end face limiting installation section.

8. The counter-rotating reduction recirculating roller screw pair according to claim 6, characterized in that: The end face cam is provided with a circumferential limiting convex portion, and the inner wall of the nut is provided with a limiting groove adapted to the circumferential limiting convex portion.

9. The counter-rotating reduction recirculating roller screw pair according to claim 6, characterized in that: A limiting retaining ring is provided between the retaining frame and the end face cam.

10. The counter-rotating reduction recirculating roller screw pair according to claim 9, characterized in that: The limiting retaining ring is a C-shaped retaining ring.

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