Differential planetary roller screw rod pair
By using an isolation ring instead of a cage in a differential planetary roller screw pair, the problems of high assembly difficulty and low transmission accuracy are solved, achieving a high-precision, reliable, and miniaturized design that can meet various application requirements.
Patent Information
- Application Number
- CN202511343571.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-19
- Publication Date
- 2025-11-21
AI Technical Summary
Existing differential planetary roller screw pairs suffer from problems such as high assembly difficulty, poor transmission accuracy and reliability, and cage structure that restricts miniaturization.
The traditional integral cage is replaced by an isolation ring. By setting a smooth bar section on the roller and adding a side opening design, the rollers are separated. Combined with elastic material and transition rounded corner structure, meshing stability and ease of assembly are ensured.
It reduces assembly difficulty, improves transmission accuracy and reliability, realizes product miniaturization and high-density integration, facilitates maintenance and parts replacement, and adapts to different loads and accuracy requirements.
Smart Images
Figure CN120991045A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of high-precision transmission technology, in particular to a differential planetary roller screw pair. BACKGROUND
[0002] The differential planetary roller screw pair is a kind of linear transmission mechanism with high precision and high bearing capacity, which is widely used in the fields of robots, aerospace and precision transmission equipment. It realizes small lead and high resolution linear displacement through the differential motion of multiple rollers between the lead screw and the nut.
[0003] The conventional differential planetary roller screw pair has adjacent first and second meshing sections on the roller, and the first and second meshing sections have a large diameter difference. The first meshing section is engaged with the outer thread of the lead screw, and the second meshing section is engaged with the zero lead internal thread in the nut. In addition, the nut interior is also provided with an avoidance section for accommodating the first meshing section. In order to avoid the phenomenon of stacking or mutual collision of the rollers during movement, a retaining ring in the form of a ring is usually arranged between the rollers, and a roller positioning hole corresponding to the roller is arranged on the retaining ring.
[0004] However, the conventional differential planetary roller screw pair has the following technical limitations:
[0005] (1) The retaining ring is an integral ring structure, and due to the large diameter difference between the avoidance section in the nut and the zero lead internal thread, the assembly difficulty is large, especially in the miniaturization or micro-miniaturization design where the radial space is limited.
[0006] (2) The matching gap between the retaining ring and the roller is difficult to accurately control, affecting the transmission accuracy and reliability.
[0007] (3) The retaining ring needs to be provided with a central through hole for the lead screw to pass through and circumferentially distributed roller positioning holes. In order to meet its own structural strength requirements, sufficient radial space needs to be reserved, which restricts the development of the differential planetary roller screw pair to smaller sizes. SUMMARY
[0008] The technical problem to be solved by the present application is to solve the technical deficiencies of the differential planetary roller screw pair in the prior art, such as large assembly difficulty, poor transmission accuracy and reliability, and the structure of the retaining ring restricting the development of the differential planetary roller screw pair to smaller sizes.
[0009] In order to solve the above technical problems, the technical scheme provided by the present application is as follows: a differential planetary roller screw pair, at least comprising: a lead screw, the outer periphery of the lead screw is provided with a transmission external thread; The inner periphery of the nut is sequentially provided with a clearance section and a zero lead internal thread section, and the inner diameter of the clearance section is greater than the maximum inner diameter of the zero lead internal thread section; A plurality of rollers are arranged between the screw rod and the nut, and the rollers are provided with a first meshing section meshing with the transmission external thread and a second meshing section meshing with the zero lead internal thread section, and the first meshing section is located in the clearance section; The middle part of the first meshing section is provided with a polished rod section; Further comprising an isolation ring sleeved on the polished rod section, the isolation ring comprises a receiving cavity in gap cooperation with the polished rod section and an opening for the polished rod section to enter the receiving cavity, the included angle of the receiving cavity is greater than 180°, and the opening is towards the screw rod; The wall thickness of the isolation ring is greater than the radial height from the maximum radial dimension of the first meshing section to the polished rod section; The outer wall of the isolation ring and the inner wall of the clearance section have a gap.
[0010] In a preferred embodiment, the difference between the wall thickness of the isolation ring and the radial height from the maximum radial dimension of the first meshing section to the polished rod section is not less than 0.05mm.
[0011] In a preferred embodiment, the isolation ring is made of elastic material.
[0012] In a preferred embodiment, the outer ring included angle of the isolation ring is greater than the inner ring included angle.
[0013] In a preferred embodiment, the outer ring included angle of the isolation ring is 270°-330°, and the inner ring included angle is 200°-240°.
[0014] In a preferred embodiment, a transition section is arranged at the opening, and the wall thickness of the transition section gradually decreases from the inner ring included angle termination position to the outer ring included angle termination position.
[0015] In a preferred embodiment, a fillet is arranged between the outer ring included angle termination position and the transition section at the opening.
[0016] In the differential planetary roller screw pair of the present application, the isolation ring arranged on each roller realizes the separation between the rollers, replaces the function of the traditional integral retainer, and the opening design ensures the normal meshing of the first meshing section and the transmission external thread of the screw rod, and the following beneficial effects are achieved:
[0017] (1) The isolation ring adopts a lateral opening design, can be directly clamped into the polished rod section from the radial direction, saves the axial installation and precise positioning process required by the traditional retainer, greatly reduces the assembly difficulty in narrow space, and is especially beneficial to the manufacturing and assembly of miniaturized and high-density integrated products, and the assembly convenience and assembly efficiency are greatly improved.
[0018] (2) The gap between the isolation ring and the polished rod section is matched, the included angle of the accommodating cavity is greater than 180°, each roller can be reliably isolated, the mutual collision and stacking between the rollers during movement are effectively prevented, so that the transmission process is stable and reliable, and the overall transmission precision and reliability are improved.
[0019] (3) Compared with the center through hole and the circumferential roller positioning hole structure required by the traditional retainer, the isolation ring is directly embedded in the gap between the roller polished rod section and the nut avoidance section, which greatly saves the radial installation space and makes the structure more compact, which provides the possibility for further miniaturization and lightweight design of the product.
[0020] (4) The design of the opening towards the screw rod, combined with the optional elastic material and the transition fillet structure, can effectively lock the isolation ring after installation, and is easy to operate when disassembled, which greatly facilitates the later maintenance and part replacement.
[0021] (5) The innovative structure of the outer ring included angle being greater than the inner ring included angle, on the one hand, uses the large included angle of the outer ring to ensure the overall strength and stability of the isolation ring, and on the other hand, with the help of the small included angle of the inner ring, the assembly difficulty is reduced, the structure design is scientific, and the strength and assembly convenience are considered, and the effective unity of reliability and easy assembly and disassembly is realized.
[0022] (6) By adjusting the inner and outer included angles, wall thickness difference and opening transition structure of the isolation ring, the assembly convenience and working stability can be further balanced to meet the application requirements of different loads, speeds and precision requirements, and good engineering adaptability and design freedom are shown. BRIEF DESCRIPTION OF DRAWINGS
[0023] Figure 1 It is an internal structure schematic diagram of the differential planetary roller screw pair shown in embodiment one; Figure 2 It is an A-A sectional view schematic diagram shown in Figure 1 Figure 3 It is a perspective state structure schematic diagram of the structure shown in Figure 1 Figure 4 It is a perspective structure schematic diagram of the isolation ring in embodiment one; Figure 5 It is a front view structure schematic diagram of the isolation ring shown in Figure 4 Figure 6 It is a structure schematic diagram of the roller in embodiment one; Figure 7 It is a structure schematic diagram of the nut in embodiment one; Figure 8 It is an internal partial structure schematic diagram of the differential planetary roller screw pair shown in embodiment two; Figure 9 This is a schematic diagram of the roller structure in Example 2.
[0024] Among them, 10-isolation ring, 11-accommodating cavity, 12-opening, 13-inner ring, 14-outer ring, 15-transition section, 16-rounded corner; 20-roller, 21-first engagement section, 22-second engagement section, 23-polished rod section; 30-nut, 31-clearance section, 32-zero lead internal thread section; 40-lead screw. Detailed Implementation
[0025] 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.
[0026] 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.
[0027] 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.
[0028] Example 1
[0029] This embodiment describes a differential planetary roller screw pair, such as... Figures 1-3 As shown, it includes a nut 30, a lead screw 40, a plurality of rollers 20 disposed between the lead screw 40 and the nut 30, and a spacer ring 10 disposed on each roller 20. The lead screw 40 has a transmission external thread on its outer periphery.
[0030] In this embodiment, the structure of the nut 30 is as follows: Figure 7 As shown, its inner circumference is provided with a clearance section 31 and zero-lead internal thread sections 32 adjacent to both sides of the clearance section 31. The inner diameter of the clearance section 31 is larger than the maximum inner diameter of the zero-lead internal thread section 32, and the diameter difference between the two is relatively large.
[0031] In this embodiment, the structure of the roller 20 is as follows: Figure 6As shown, the first engagement section 21 is engaged with the external thread of the transmission, and the second engagement section 22 is located on both sides of the first engagement section 21. The second engagement section 22 is provided with a zero lead external thread section for engaging with the zero lead internal thread section 32. The first engagement section 21 is located in the clearance section 31 of the nut 30.
[0032] As a particularity of the present embodiment, the middle part of the first engagement section 21 is provided with a polished rod section 23 for sleeving the isolating ring 10.
[0033] As a particularity of the present embodiment, the isolating ring 10 is structured as shown in Figures 4-5 , which includes a receiving cavity 11 in clearance fit with the polished rod section 23 and an opening 12 for the polished rod section 23 to enter the receiving cavity 11. As shown in Figure 2 , the included angle of the receiving cavity 11 is greater than 180°, and the opening 12 is directed towards the lead screw 40.
[0034] In the present embodiment, the isolating ring 10 is usually made of a material with certain elasticity, such as engineering plastics, resin, metal elastic material, etc., which facilitates the radial clamping of the isolating ring into the polished rod section of the roller. In the present embodiment, a wear-resistant, low-friction or high-strength material is preferably selected. Of course, in the present embodiment, the specific material is not limited to rotation, and those skilled in the art can select from existing materials according to design requirements.
[0035] In the present embodiment, the wall thickness of the isolating ring 10 is greater than the maximum radial dimension of the first engagement section to the radial height of the polished rod section 23. After such arrangement, since the receiving cavity 11 of the isolating ring 10 is in clearance fit with the polished rod section 23, even if the isolating ring is not concentric with the polished rod section, the effective isolation between adjacent rollers can be ensured, and the collision and stacking between adjacent rollers can be prevented.
[0036] In the present embodiment, the difference between the wall thickness of the isolating ring 10 and the maximum radial dimension of the first engagement section to the radial height of the polished rod section 23 is usually not less than 0.05 mm, which can be designed according to different loads, rotational speeds and accuracy requirements, etc.
[0037] In the present embodiment, there is a gap between the outer wall of the isolating ring 10 and the inner wall of the clearance section 31 to prevent friction and interference when the nut 30 linearly displaces relative to the lead screw 40.
[0038] As a particularity of the present embodiment, as shown in Figure 4 , Figure 5As shown, the wrap angle of the outer ring 14 of the isolation ring 10 is greater than that of the inner ring 13. Generally, the outer ring wrap angle is 270°-330°, and the inner ring wrap angle is 200°-240°. The purpose of such arrangement is to ensure the overall strength and stability of the isolation ring by virtue of the large wrap angle of the outer ring, and to reduce the assembly difficulty by virtue of the small wrap angle of the inner ring, so that the strength and the assembly convenience are considered, and the effective unity of reliability and easy assembly and disassembly is achieved.
[0039] As a particularity of the present embodiment, the opening 12 is provided with a transition section 15, and the wall thickness of the transition section 15 gradually decreases from the inner ring wrap angle termination position to the outer ring wrap angle termination position. The purpose of such arrangement is to play a guiding role when the isolation ring and the polished rod section are disassembled, so as to facilitate the disassembly convenience between the isolation ring and the polished rod section.
[0040] As a particularity of the present embodiment, the opening 12 is provided with a transition section 15, and the wall thickness of the transition section 15 gradually decreases from the inner ring wrap angle termination position to the outer ring wrap angle termination position. The purpose of such arrangement is to play a guiding role when the isolation ring and the polished rod section are disassembled, so as to facilitate the disassembly convenience between the isolation ring and the polished rod section.
[0041] Embodiment Two
[0042] The differential planetary roller screw pair of the present embodiment, as shown in Figure 8 , Figure 9 the difference between the present embodiment and the first embodiment lies in the structural form of the roller 20 and the nut 30.
[0043] Specifically, in the present embodiment, the roller 20 includes a second engagement section 22 engaged with the zero lead internal thread section 32 of the nut 30, and first engagement sections 21 adjacent to both sides of the second engagement section 22, which are used to engage with the transmission external thread on the screw. And the middle part of the two first engagement sections 21 is provided with a polished rod section 23 for sleeving the isolation ring 10.
[0044] Correspondingly, the nut 30 is provided with a zero lead internal thread section 32 and a clearance section 31 adjacent to both sides of the zero lead internal thread section 32.
[0045] 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 differential planetary roller screw mechanism, comprising at least: a screw rod, an outer periphery of the screw rod being provided with a driving external thread; a nut, an inner periphery of the nut being provided with a clearance section and a zero lead internal thread section in sequence, an inner diameter of the clearance section being greater than a maximum inner diameter of the zero lead internal thread section; a plurality of rollers, configured between the screw rod and the nut, the rollers being provided with a first engagement section engaging with the driving external thread and a second engagement section engaging with the zero lead internal thread section, the first engagement section being located in the clearance section; characterized in that a middle part of the first engagement section is provided with a smooth rod section; further comprising an isolation ring sleeved on the smooth rod section, the isolation ring comprising a receiving cavity gap-fitting with the smooth rod section and an opening for the smooth rod section to enter the receiving cavity, an included angle of the receiving cavity being greater than 180°, the opening being towards the screw rod; a wall thickness of the isolation ring being greater than a radial height from a maximum radial dimension of the first engagement section to the smooth rod section; a gap being provided between an outer wall of the isolation ring and an inner wall of the clearance section.
2. The differential planetary roller screw pair according to claim 1, wherein, a difference between the wall thickness of the isolation ring and the radial height from the maximum radial dimension of the first engagement section to the smooth rod section is not less than 0.05 mm.
3. The differential planetary roller screw pair according to claim 1, wherein, the isolation ring is made of an elastic material.
4. A differential planetary roller screw pair according to any one of claims 1 to 3, characterized in that an outer ring included angle of the isolation ring is greater than an inner ring included angle.
5. The differential planetary roller screw pair according to claim 4, wherein, the outer ring included angle of the isolation ring is 270°-330°, and the inner ring included angle is 200°-240°.
6. The differential planetary roller screw pair according to claim 4, wherein, a transition section is provided at the opening, a wall thickness of the transition section gradually decreasing from an inner ring included angle end position to an outer ring included angle end position.
7. The differential planetary roller screw pair according to claim 6, characterized in that a fillet is provided between the outer ring included angle end position and the transition section at the opening.