Circulating planetary roller screw

Abstract

This invention discloses a circulating planetary roller screw, comprising a screw, rollers, a nut, a cage, a retaining ring, a guide key, and a locating pin. The screw has a single-start or multi-start external thread; the rollers have multiple annular teeth; the nut has internal threads with the same direction and number of starts as the screw, and internally machined with a keyway that mates with the guide key; the cage has a shaped through groove that mates with the rollers; the retaining ring has a thin-walled annular structure and a radial position guiding structure for the rollers; the guide key has multiple sets of parallel shaped grooves; and the locating pin is used to fix the guide grooves and the nut. The retaining ring, guide key, and cage work together to achieve omnidirectional constraint of the radial and axial positions during the roller circulation process; the roller annular teeth simultaneously mesh with the screw and nut threads, realizing the conversion of the screw's rotational motion into the nut's linear motion. This invention has the advantages of continuous and smooth roller motion and low motion impact, and can meet the high-speed, heavy-load drive requirements of small lead and high transmission ratio.

Description

Technical Field

[0001] This invention belongs to the field of mechanical transmission technology, specifically relating to a circulating planetary roller screw. Background Technology

[0002] A recirculating planetary roller screw is a precision transmission mechanism that transmits power and motion through the helical meshing of multiple rollers with a screw and nut. Unlike standard planetary roller screws, recirculating planetary roller screws can have as few as two or even one lead, making it easier to achieve small lead and high transmission ratio motion requirements. It has promising applications in high-power-density electromechanical actuators and precision motion control.

[0003] In existing recirculating planetary roller screws (Satellite roller screws [M]. Geneva:Rollivs, 2008, www.rollivs.com), to ensure the rollers can achieve position circulation, a cam structure installed at both ends of the nut and a structure that cuts off the helix of the nut are used to control and change the axial position of the rollers. This structure causes the recirculating planetary roller screw to generate relatively large internal impacts during operation (Guan Qiao, Rong Liao, Shijie, et al. Design and dynamic analysis of the recirculating planetary rollerscrew mechanism[M], Chinese Journal of Mechanical Engineering, 35(2022),2022, 1-16), and these impacts are more pronounced at high speeds. This severely restricts the application of recirculating planetary roller screws in high-speed, high-dynamic applications. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a circulating planetary roller screw, comprising a screw, rollers, a nut, a cage, a retaining ring, a guide key, and a locating pin. The screw has a single-start or multi-start external thread; the rollers have multiple annular teeth; the nut has internal threads with the same direction and number of starts as the screw, and internally machined with a keyway that mates with the guide key; the cage has a shaped through-groove that mates with the rollers; the retaining ring has a thin-walled annular structure and a radial position guiding structure for the rollers; the guide key has multiple sets of parallel shaped grooves; and the locating pin is used to fix the guide key and the nut. The retaining ring, guide key, and cage work together to achieve omnidirectional constraint of the radial and axial positions during the roller circulation process; the roller annular teeth simultaneously mesh with the internal threads of the screw and nut, realizing the conversion of the screw's rotational motion into the nut's linear motion. This invention has the advantages of continuous and smooth roller motion and low motion impact, and can meet the high-speed, heavy-load drive requirements of small lead and high transmission ratio.

[0005] The technical solution adopted by this invention to solve its technical problem includes the following steps:

[0006] A circulating planetary roller screw includes a screw 1, rollers 2, a nut 3, a cage 4, a retaining ring 5, a guide key 6, and a locating pin 7;

[0007] The lead screw 1 has a single-start or multi-start thread; the middle section of the roller 2 has multiple annular tooth structures 2-1, and the spacing between the annular tooth structures 2-1 is equal to the pitch of the lead screw 1; the two ends of the roller 2 are optical shafts 2-2.

[0008] The nut 3 includes a single-start or multi-start internal thread 3-1; the nut 3 has a keyway structure 3-2 inside; the two ends of the nut 3 have a cage mounting surface structure 3-3 and a locating pin mounting hole structure 3-4; the annular tooth structure 2-1 of the roller 2 meshes with the thread of the lead screw 1 and the internal thread 3-1 of the nut 3.

[0009] The retainer 4 includes a plurality of evenly distributed irregularly shaped through slots 4-2, which mate with the optical axis 2-2; the outer circular structure 4-1 of the retainer 4 and the retainer mounting surface structure 3-3 mate with each other.

[0010] The fixing ring 5 includes an annular base 5-1, a roller radial drive boss 5-2, and an inner groove 5-3; the annular base 5-1 and the cage mounting surface structure 3-3 are matched.

[0011] The guide key 6 includes a mounting base 6-1, multiple sets of parallel irregular grooves 6-2, a cage mating surface 6-3, and a positioning pin mounting hole 6-4;

[0012] The internal thread 3-1 in the nut 3 is cut off by the keyway structure 3-2; the mounting base 6-1 of the guide key 6 cooperates with the keyway structure 3-2, and the guide key 6 is fixed in the axial position of the nut 3 by using a positioning pin 7 passing through the positioning pin mounting hole 6-4 and the positioning pin mounting hole structure 3-4.

[0013] The internal thread 3-1 at the installation position of the guide key 6 is inclined upward, the irregular groove 6-2 in the guide key 6 is inclined downward, and the two ends of the irregular groove 6-2 are connected to the thread groove on the edge of the keyway structure 3-2, forming a closed loop groove between the internal thread 3-1 of the nut and the irregular groove 6-2 in the guide key.

[0014] A retainer 4 is installed at the retainer mounting surface structure 3-3 at one end of the nut 3, and then a retaining ring 5 is installed. The retaining ring 5 is fixed to the nut 3 by interference fit through the annular base 5-1 and the retainer mounting surface structure 3-3 at the end of the nut 3. The roller 2 is installed through the irregular through groove 4-2 on the retainer 4. The retainer 4 and retaining ring 5 are installed at the retainer mounting surface structure 3-3 at the other end of the nut 3. The lead screw 1 is rotated into the virtual internal thread formed by multiple rollers 2 to complete the assembly of the cyclic planetary roller lead screw.

[0015] Preferably, the roller radial drive boss 5-2 and the guide key 6 on the fixing ring 5 have the same mounting phase angle;

[0016] Preferably, a gap of 0.2 mm is reserved between the fixing ring 5 and the retainer 4.

[0017] Preferably, the distance between the parallel irregular grooves 6-2 in the guide key 6 is equal to the pitch of the internal thread 3-1; let the number of irregular grooves 6-2 in the guide key 6 be N, and the number of teeth of the internal thread 3-1 be at least N+2.

[0018] Preferably, when the lead screw 1 rotates, the roller 2 will roll along the internal thread 3-1 of the nut 3, and the axial position of the roller 2 relative to the nut 3 will change as the roller 2 rolls; when the roller 2 moves to the position of the roller radial drive boss 5-2 on the fixed ring 5, it will generate a certain radial displacement with the drive boss, thereby causing the roller annular tooth structure 2-1 to disengage from the thread teeth of the lead screw 1; at the same time, the roller annular tooth structure 2-1 will be constrained by the guide key 6 irregular groove 6-2 and generate a certain axial displacement, completing the transformation of the position of the roller 2 in the guide key 6; each annular tooth 2-1 of the roller 2 will circulate along the circular groove formed by the internal thread 3-1 of the nut 3 and the guide key 6 irregular groove 6-2.

[0019] The beneficial effects of this invention are as follows:

[0020] 1. This invention differs from existing circulating planetary roller screws by adding guide keys and retaining ring components. The retaining ring, guide keys, and cage work together to achieve all-round constraint on the radial, axial, and tangential motion trajectories during the roller circulation process.

[0021] 2. This invention has the advantages of continuous and smooth roller motion and low motion impact, and can meet the high-speed heavy-load drive requirements of small lead and high transmission ratio.

[0022] 3. This invention can significantly improve the maximum limiting speed of the circulating planetary roller screw, reduce the internal impact load, and increase its service life. Attached Figure Description

[0023] Figure 1 This is a three-dimensional schematic diagram of the lead screw of the present invention.

[0024] Figure 2 This is a three-dimensional schematic diagram of the lead screw structure of the present invention.

[0025] Figure 3 This is a three-dimensional schematic diagram of the roller structure of the present invention.

[0026] Figure 4 This is a three-dimensional schematic diagram of the nut structure of the present invention.

[0027] Figure 5 This is a three-dimensional schematic diagram of the cage structure of the present invention.

[0028] Figure 6 This is a three-dimensional schematic diagram of the fixed ring structure of the present invention.

[0029] Figure 7 This is a three-dimensional schematic diagram of the guide key structure of the present invention.

[0030] Figure 8 This is a three-dimensional schematic diagram of the assembly of the nut and guide key of the present invention.

[0031] Figure 9 This is a schematic cross-sectional view of the circulating planetary roller screw of the present invention at the fixed ring position and perpendicular to the axis.

[0032] Figure 10 This is a schematic cross-sectional view of the circulating planetary roller screw of the present invention at the position of the roller annular tooth and perpendicular to the axis.

[0033] Figure 11 This is a schematic cross-sectional view of the circulating planetary roller screw of the present invention in which the roller 2-a engages with the screw and the guide key.

[0034] Figure 12 This is a schematic cross-sectional view of the circulating planetary roller screw of the present invention in which the roller 2-b meshes with the screw and nut.

[0035] Figure descriptions: 1. Lead screw; 2. Roller; 3. Nut; 4. Cage; 5. Retaining ring; 6. Guide key; 7. Locating pin; 2-1. Annular tooth structure; 2-2. Optical shaft; 3-1. Internal thread; 3-2. Keyway structure; 3-3. Cage mounting surface structure; 3-4. Locating pin mounting hole structure; 4-1. Outer circle structure; 4-2. Irregular through groove; 5-1. Annular base; 5-2. Roller radial drive boss; 5-3. Inner groove; 6-1. Mounting base; 6-2. Parallel irregular groove; 6-3. Cage mating surface; 6-4. Locating pin mounting hole; 7 roller positions are numbered counterclockwise: 2-a, 2-b, 2-c, 2-d, 2-e, 2-f, and 2-g. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0037] To improve the smoothness of the internal roller movement of a circulating planetary roller screw, reduce the impact load on the rollers during the circulation process, and increase the limit input speed of the transmission mechanism, this invention provides a roller circulation device and a circulating planetary roller screw.

[0038] Unlike existing cyclic planetary roller screws, this invention utilizes multiple sets of parallel irregular groove structures in the guide key (the number of irregular grooves equals the number of roller ring teeth), the roller radial guide structure in the fixed ring, and the cage straight groove structure to achieve all-round control of radial, axial, and tangential motion during roller circulation. This enables rapid, continuous, and low-impact positional transition of the roller within the nut.

[0039] To achieve the above objectives, the technical solution of the present invention is: a roller circulation device and a circulating planetary roller screw, comprising a screw, rollers, a nut, a cage, a retaining ring, a guide key, and a locating pin. The screw has a single-start or multi-start external thread; the rollers have multiple annular teeth, the spacing of which is equal to the screw pitch; the nut has internal threads with the same direction and number of starts as the screw, and internally machined with a keyway that mates with the guide key; the cage has a shaped through groove that mates with the rollers; the retaining ring has a thin-walled annular structure and a roller radial position guiding structure; the guide key has multiple sets of parallel shaped grooves for axial position guidance of the rollers.

[0040] Furthermore, the nut has an internal keyway structure that cuts off the single- or multi-start helix. A guide key is installed into the keyway of the nut, and a locating pin is used to fix the axial position of the guide key relative to the nut.

[0041] Furthermore, the distance between the parallel irregular grooves in the guide key is equal to the pitch of the nut thread; if we assume that the number of irregular grooves in the guide key is N, the number of threads in the nut thread should be at least N+2.

[0042] Furthermore, the inclination direction of the irregular groove in the guide key is opposite to the inclination direction of the thread at its installation position, and the two ends of the irregular groove are connected to the thread groove at the edge of the nut keyway.

[0043] Furthermore, the irregular grooves in the nut thread and guide key form N closed circular grooves.

[0044] Furthermore, a retainer is installed at the opening at one end of the nut, and finally a retaining ring is installed. The retaining ring can be secured to the nut by a locating pin, thread, or slight interference fit.

[0045] Furthermore, the roller radial guide structure on the retaining ring should have the same installation phase angle as the guide key parts, and a certain gap should be reserved between the retaining ring and the cage.

[0046] Furthermore, the rollers are installed using the irregular through grooves on the cage, and the number of annular teeth on the rollers is no more than N.

[0047] Furthermore, a retainer and a retaining ring are installed at the opening at the other end of the nut to ensure that the radial roller guide structure on the retaining ring has the same installation phase angle as the guide key parts.

[0048] Furthermore, the lead screw is rotated and inserted into a virtual internal thread formed by multiple rollers to complete the assembly of the cyclic planetary roller lead screw.

[0049] Furthermore, as the leadscrew rotates, the rollers roll along the internal thread of the nut, and the axial position of the rollers relative to the nut changes as they roll. When the rollers reach the radial guide structure on the fixed ring, they undergo a certain radial displacement due to the guide structure, causing the roller ring teeth to disengage from the leadscrew thread teeth. Simultaneously, the roller ring teeth are constrained by the guide key's groove and undergo a certain axial displacement, completing the roller position transformation within the guide key. Therefore, each ring tooth of the roller will circulate along the N closed annular grooves formed by the nut thread and the guide key's groove.

[0050] Furthermore, the rotational freedom of the nut is constrained. When the lead screw rotates one revolution, the distance the nut moves forward or backward along the lead screw axis is equal to the lead screw's lead. Specific Implementation

[0051] like Figure 1 As shown, a roller circulation structure and a circulating planetary roller screw include a screw 1, a roller 2, a nut 3, a cage 4, a retaining ring 5, a guide key 6, and a locating pin 7.

[0052] like Figure 2 As shown, the lead screw 1 has a single-start or multi-start thread. In this embodiment, the number of thread starts on the lead screw 1 is N. s=2, pitch is P=2mm, and thread pitch diameter of lead screw 1 is 19.5mm.

[0053] like Figure 3 As shown, the middle section of roller 2 has multiple annular tooth structures 2-1, and the spacing between the annular teeth 2-1 is equal to the screw pitch P=2mm; both ends of roller 2 are optical shafts 2-2. The optical shafts 2-2 mate with the irregular grooves 4-2 in the cage 4; the annular teeth 2-1 of roller 2 mesh with the threads of screw 1 and nut 2; the nominal diameter of the annular teeth 2-1 of roller 2 is 6.5mm, and the number of annular teeth is 20.

[0054] like Figure 4 As shown, the nut 3 has a single-start or multi-start internal thread 3-1. In this embodiment, the internal thread 3-1 of the nut 3 has 2 starts and a pitch of P=2mm. The nut 3 has a guide key 6 and a keyway 3-2 inside. The two ends of the nut 3 have a retainer mounting surface structure 3-3 and a locating pin mounting hole structure 3-4. The mean diameter of the internal thread 3-1 of the nut 3 is 32.5mm, and the number of thread teeth is 22.

[0055] like Figure 5 As shown, the cage 4 has multiple evenly distributed irregular grooves 4-2; the outer circular structure 4-1 of the cage 4 and the 3-3 structure in the nut 3 cooperate with each other.

[0056] like Figure 6 As shown, the retaining ring 5 is composed of an annular base 5-1, a roller radial drive boss 5-2, and an inner groove 5-3. The annular base 5-1 structure cooperates with the cage mounting surface structure 3-3 in the nut 3.

[0057] like Figure 7 As shown, the guide key 6 has a mounting base 6-1, multiple sets of parallel irregular grooves 6-2, a retainer mating surface 6-3, and a locating pin mounting hole 6-4. In this embodiment, the number of multiple sets of parallel irregular grooves 6-2 is 20.

[0058] like Figure 8 As shown, the multi-start helix in nut 3 is interrupted by the keyway structure 3-2. The mounting base 6-1 of guide key 6 mates with the nut keyway 3-2, and the axial position of the guide key relative to the nut is fixed using locating pin holes 6-4 and 3-4. Figure 8 As shown, the internal thread 3-1 of the nut at the installation position of the guide key 6 is inclined upwards, and the irregular groove 6-2 in the guide key 6 is inclined downwards. The two ends of the irregular groove 6-2 are connected to the threaded grooves on the edge of the nut keyway. In this embodiment, 20 closed circular grooves are formed between the internal thread 3-1 of the nut and the irregular groove 6-2 in the guide key.

[0059] In this embodiment, a retainer 4 is installed at the opening 3-3 at one end of the nut, and finally a retaining ring 5 is installed. The retaining ring is fixed to the nut by a small interference fit between 5-1 and the nut end 3-3, and the roller radial guide structure 5-2 on the retaining ring 5 should have the same installation phase angle as the guide key 6. A gap of 0.2mm is reserved between the retaining ring 5 and the retainer 4.

[0060] The rollers 2 are installed using the irregular through-groove 4-2 on the cage, and the rollers 2 have 20 annular teeth 2-1. In this embodiment, there are 7 rollers. Then, the cage 4 and retaining ring 5 are installed at the opening 3-3 at the other end of the nut, ensuring that the radial guide structure 5-2 on the retaining ring has the same installation phase angle as the guide key 6. Finally, the lead screw 1 is rotated into the virtual internal thread formed by the multiple rollers 2, completing the assembly of the cyclic planetary roller lead screw.

[0061] like Figure 9 and Figure 10 As shown, the seven roller positions in this embodiment are numbered 2-a, 2-b, 2-c, 2-d, 2-e, 2-f, and 2-g in a counter-clockwise direction. When the roller is in position 2-a, the roller pin 2-2 contacts the highest point of the radial guide structure 5-2 of the fixed ring roller. As a result, the radial distance of the roller in position 2-a will be larger than in other positions, and when the roller is in position 2-a, the roller ring tooth 2-1 does not engage with the screw thread 1, but engages with the irregular groove 6-2 in the guide key. When the roller is in positions 2-b to 2-g, the ring tooth 2-1 engages with both the screw and nut threads simultaneously.

[0062] In this embodiment, when the roller is at position 2-a, its axial movement is constrained by the irregular groove 6-2 in the guide key 6, its radial movement is constrained by the radial drive boss 5-2 of the fixed ring 5 roller, and its tangential movement is constrained by the irregular through groove 4-2 of the cage. A cross-sectional schematic diagram of the circulating planetary roller screw in engagement with the screw and guide key at roller 2-a is shown below. Figure 11 As shown in the diagram. A cross-sectional view of the recirculating planetary roller screw where roller 2-b engages with the screw and nut is shown below. Figure 12 As shown. When the roller is in position 2-b to 2-g, the roller 2 is driven by the screw 1 thread and will roll along the multi-start internal thread 3-1 of the nut 3, and will produce a certain axial movement relative to the nut.

[0063] When the lead screw is Figure 9 When rotated counterclockwise in the direction shown, the roller 2 will circulate along the 20 closed annular grooves formed by the nut internal thread 3-1 and the guide key groove 6-2.

Claims

1. A circulating planetary roller screw, characterized in that, It includes a lead screw (1), rollers (2), nuts (3), cages (4), retaining rings (5), guide keys (6), and locating pins (7); The lead screw (1) has a single-start or multi-start thread; the middle section of the roller (2) has multiple annular tooth structures (2-1), and the spacing between the annular tooth structures (2-1) is equal to the pitch of the lead screw (1); the two ends of the roller (2) are optical shafts (2-2). The nut (3) includes a single-start or multi-start internal thread (3-1); the nut (3) has a keyway structure (3-2) inside; the two ends of the nut (3) have a cage mounting surface structure (3-3) and a locating pin mounting hole structure (3-4); the annular tooth structure (2-1) of the roller (2) meshes with the thread and internal thread (3-1) of the lead screw (1); The retainer (4) includes a plurality of evenly distributed irregular through slots (4-2), which are matched with the optical axis (2-2); the outer circular structure (4-1) of the retainer (4) and the retainer mounting surface structure (3-3) are matched. The fixing ring (5) includes an annular base (5-1), a roller radial drive boss (5-2), and an inner groove (5-3); the annular base (5-1) and the cage mounting surface structure (3-3) cooperate with each other; The guide key (6) includes a mounting base (6-1), multiple sets of parallel irregular grooves (6-2), a cage mating surface (6-3), and a positioning pin mounting hole (6-4). The internal thread (3-1) in the nut (3) is cut off by the keyway structure (3-2); the mounting base (6-1) of the guide key (6) is engaged with the keyway structure (3-2), and the guide key (6) is fixed in the axial position of the nut (3) by a positioning pin (7) passing through the positioning pin mounting hole (6-4) and the positioning pin mounting hole structure (3-4); The internal thread (3-1) at the installation position of the guide key (6) is inclined upward, the irregular groove (6-2) in the guide key (6) is inclined downward, and the two ends of the irregular groove (6-2) are connected to the thread groove at the edge of the keyway structure (3-2), forming a closed loop groove between the internal thread (3-1) of the nut and the irregular groove (6-2) in the guide key; Install a retainer (4) at the retainer mounting surface structure (3-3) at one end of the nut (3), and then install a retaining ring (5); the retaining ring (5) is fixed to the nut (3) by interference fit through the annular base (5-1) and the retainer mounting surface structure (3-3) at the end of the nut (3); the roller (2) is installed through the special through groove (4-2) on the retainer (4); the retainer (4) and retaining ring (5) are installed at the retainer mounting surface structure (3-3) at the other end of the nut (3); rotate the screw (1) into the virtual internal thread formed by multiple rollers (2) to complete the assembly of the cyclic planetary roller screw; The roller radial drive boss (5-2) and guide key (6) on the fixed ring (5) have the same installation phase angle.

2. The circulating planetary roller screw according to claim 1, characterized in that, A gap of 0.2 mm is reserved between the fixing ring (5) and the retainer (4).

3. The circulating planetary roller screw according to claim 1, characterized in that, The distance between the parallel irregular grooves (6-2) in the guide key (6) is equal to the pitch of the internal thread (3-1); let the number of irregular grooves (6-2) in the guide key (6) be N, and the number of teeth of the internal thread (3-1) be at least N+2.

4. The circulating planetary roller screw according to claim 1, characterized in that, When the lead screw (1) rotates, the roller (2) will roll along the internal thread (3-1) of the nut (3), and the axial position of the roller (2) relative to the nut (3) will change as the roller (2) rolls. When the roller (2) moves to the position of the roller radial drive boss (5-2) on the fixed ring (5), it will generate a certain radial displacement with the drive boss, thereby causing the roller ring tooth structure (2-1) to disengage from the thread teeth of the lead screw (1). At the same time, the roller ring tooth structure (2-1) will be constrained by the guide key (6) groove (6-2) and generate a certain axial displacement, completing the transformation of the position of the roller (2) in the guide key (6). Each ring tooth structure (2-1) of the roller (2) will circulate along the circular groove formed by the internal thread (3-1) of the nut (3) and the guide key (6) groove (6-2).

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