An annular tooth roller screw transmission mechanism

Abstract

The present invention provides a ring-shaped roller screw transmission mechanism, comprising a screw, a roller, a nut, a retaining frame, an inner gear ring, and a locating pin. The screw has a multi-start external thread, and the rollers have smooth axes at both ends. The middle section has multiple annular protrusions and both ends are machined with straight teeth. The rollers are distributed around the screw, and the roller protrusions mesh with the screw threads. The nut has annular recesses inside that mesh with the roller protrusions. The inner gear ring is installed in a groove on the inner wall of the nut and is installed with a fixed phase angle. The straight teeth of the inner gear ring mesh with the straight teeth of the rollers. The retaining frame is installed in a groove on the inner wall of the nut, and the smooth axes at both ends of the rollers match the U-shaped grooves of the retaining frame. The present invention can achieve a smaller radial dimension than a standard planetary roller screw under the same screw center diameter state. It can also improve the uneven load-bearing characteristics of long rollers with multiple threads by utilizing multiple sets of rollers.

Description

Technical Field

[0001] The present invention belongs to the technical field of mechanical transmission, and in particular relates to a roller screw transmission mechanism, which is particularly suitable for transmission under heavy-load conditions in a limited installation space. Background Art

[0002] A planetary roller screw is a precision transmission mechanism and rolling component that transmits power and motion through the curved meshing of multiple rollers, a screw, and a nut. As the actuator of an electromechanical servo system, a planetary roller screw can significantly increase its power density, replacing high-thrust hydraulic and pneumatic servo systems and completely resolving the problems of "emission, bubbling, dripping, and leakage." This has far-reaching implications for significantly improving the operating efficiency of mechanical equipment, reducing maintenance costs, promoting the rapid development of fully electrified intelligent equipment, and promoting the development of a low-carbon, environmentally friendly economy. Currently, planetary roller screws are used in all-electric / multi-electrified equipment such as aircraft rudders, tank elevation drives, ship stabilizers, six-degree-of-freedom platforms, welding robots, and precision CNC machine tool tool feeds. They also have broad application prospects in the fully electrified development of mechanical equipment in numerous military and civilian industries, including aviation, aerospace, vehicles, petrochemicals, and robotics.

[0003] When using planetary roller screws to replace high-thrust hydraulic transmission, there is a problem that the radial size is too large and cannot be installed in related mechanical equipment. This is because in standard planetary roller screws, the screw diameter, roller diameter and nut diameter must meet the following requirements: n =Nd r and d r =d s / (N-2), where d s d r and d n d is the mean diameter of the screw, roller, and nut, respectively, and N is the number of threads in the screw and nut. (Servo Electric Cylinder and Planetary Roller Screw Comprehensive Product Manual [M]. Beijing: Doson Technology Development (Beijing) Co., Ltd., 2010, www.doson-inc.com; Satellite Roller Screws [M]. Geneva: Rollvis, 2019, www.Rollvis.com). When the mean diameter of the screw increases, the mean diameter of the roller will increase according to d. r =d s / (N-2) increases, and the radial size of the planetary roller screw will also increase significantly. The standard planetary roller screw can reduce the roller diameter by increasing the number of screw thread heads N, thereby reducing the radial size of the mechanism. However, the number of nut thread heads will increase with the increase of the number of screw thread heads N, which will greatly increase the difficulty and cost of grinding the internal thread of the nut. At the same time, when the pitch is fixed, increasing the number of nut thread heads will increase the lead and helix angle of the corresponding thread, which will increase the inclination angle of the thread grinding wheel axis, thereby limiting the minimum radial size and length of the nut. In addition, due to structural limitations and load-bearing requirements, the number of screw thread heads of the standard planetary roller screw cannot be significantly increased.

[0004] In a recirculating planetary roller screw, although the screw's pitch diameter is not proportional to the roller's pitch diameter, the rollers, as they move along the nut's threads, must periodically return to their initial positions via a specific structure or device. Furthermore, due to the difference in helix angle, the rollers and nut are constantly in a state of relative sliding at their contact points. This results in discontinuous roller movement and low efficiency during operation.

[0005] Furthermore, excessive thread counts on a single roller can exacerbate uneven load distribution (Zhang Wenjie. Calculation Model and Method for Load Distribution of Planetary Roller Screw Threads [D]. Xi'an: Doctoral Dissertation, Northwestern Polytechnical University, 2017). Secondly, the larger the roller diameter, the more severe the uneven load distribution between the roller threads on the screw and nut sides (Blinov DS, Morozov MI. Uneven load distribution between mating windings of rollers and screw withnut of planetary roller drive [J]. Science and Education of the Bauman MSTU, 2014, 9:1-14). This also limits the ability to increase the load capacity of heavy-duty planetary roller screws. Finally, existing planetary roller screws require simultaneous consideration of phase matching with the nut threads and the inner ring spur teeth during roller assembly, increasing assembly complexity.

[0006] The patent "A Planetary Roller Screw CN201210078456.0" describes a planetary roller screw with a threaded screw and an annular thread structure for the rollers and nut. This design aims to reduce the axial bulk of the entire device and facilitate assembly and disassembly. The patent states that the number of rollers in this planetary roller screw can be one or more, generally two or more, with the maximum limit being that the rollers do not interfere with each other. However, due to the combined constraints of the screw's helix angle and the nut's annular thread structure, mismatching the number of rollers and screw starts can lead to interference between the rollers and the screw. For example, if the screw has five thread starts and the rollers are evenly distributed around the screw, if the number of rollers is greater than two but not equal to five, the rollers will interfere with the screw, making assembly of the mechanism impossible. The patent "A Planetary Roller Screw CN 201210078456.0" does not address this issue. Furthermore, the patented structure cannot accommodate the parallel assembly of multiple roller groups.

[0007] The patents "Gear-Driven Planetary Roller Screw CN202010986386.3," "Ring-Geared Nut Planetary Roller Screw CN 202010984767.8," and "Planetary Roller Screw Transmission Mechanism CN 201210504715.1" all use rollers meshing at both ends of the nut to transmit the nut load. This results in a short contact section, which limits the maximum load capacity of the planetary roller screw. Furthermore, the design, in which the rollers, screw, and nut mesh at different points, subjects the rollers to significant bending moments under heavy loads. Rollers are typically slender components that struggle to withstand bending moment loads. Increasing the roller diameter to enhance its bending resistance would significantly increase the outer diameter of the nut. The patent "A Planetary Roller Screw CN202010485426.6" uses a structure in which the rollers' ends and mid-section ring teeth mesh with the nut to improve the roller's stress state. However, to achieve the same number of contact points on a single roller as a standard planetary roller screw (Servo Electric Cylinder and Planetary Roller Screw Comprehensive Product Manual [M]. Beijing: Daochen Technology Development (Beijing) Co., Ltd.), the roller length in this invention is twice that of a standard planetary roller screw. In addition, the rollers in the patent "A Planetary Roller Screw CN202010485426.6" are still subject to bending moment loads, which is not conducive to the design of small-diameter roller structures. The patent "A Nut-Type Gearless Constant-Lead Planetary Roller Screw ZL202010800383.6" is an improved design for the reverse-type planetary roller screw structure, and the screw and roller diameters must meet a certain proportional relationship. Summary of the Invention

[0008] In order to overcome the shortcomings of the existing technology, the present invention provides an annular roller screw transmission mechanism, which can obtain a smaller radial dimension than a standard planetary roller screw under the same screw middle diameter state; and utilizes multiple groups of rollers to improve the uneven load-bearing characteristics of long roller multi-thread teeth.

[0009] The technical solution adopted by the present invention to solve the technical problem is: an annular tooth roller screw transmission mechanism, including a screw, a roller, a nut, a retaining frame, an inner gear ring and a positioning pin.

[0010] The screw is a multi-start external thread with N number of threads and P pitch; the rollers have smooth axes at both ends and a plurality of annular convex teeth in the middle section, and straight teeth are processed circumferentially at both ends of the annular convex teeth, and the spacing between the annular convex teeth is equal to the screw pitch P; the rollers are distributed around the screw, and the roller convex teeth are meshed with the screw threads. The number of rollers R must satisfy R=N / Z, where Z is a positive integer, Z=1, 2, 3...; the nut has annular concave teeth inside and a plurality of circumferential grooves are arranged along the axial direction; the annular concave teeth of the nut and the annular convex teeth of the rollers mesh with each other; the retaining frame is an annular structure with a cut-off opening, and a plurality of U-shaped grooves are evenly distributed on the inner wall along the circumference; the inner gear ring is provided with an annular structure with a cut-off opening, a plurality of straight teeth are evenly distributed on the inner wall along the circumference, and a radial positioning pin hole is provided on the outer wall; the number of straight teeth of the roller is z r and the number of straight teeth z of the nut n Satisfy d r / d n =z r / z n The proportional relationship, d r and d n are the mean diameters of the roller and the nut respectively; the inner gear ring is installed in the groove of the inner wall of the nut, and the installation phase angle of the inner gear ring is fixed by a locating pin, and the spur teeth of the inner gear ring are engaged with the spur teeth of the roller; the retaining frame is installed in the groove of the inner wall of the nut, and the optical axes at both ends of the roller match the U-shaped grooves of the retaining frame.

[0011] Furthermore, a plurality of rollers having the same axial position around the screw is defined as a group, and X groups are installed along the axial direction of the screw, where X=1, 2, 3, ... . . .

[0012] Furthermore, when there are more than two groups of rollers, different meshing clearances are designed between each group of rollers and the screw and nut according to the state of the external load on the nut and the screw, so that each group of rollers bears the same load.

[0013] Furthermore, the installation interval angle of each roller in a group of rollers is equal to Z×360° / N.

[0014] Furthermore, a process groove is provided on the inner wall of the retainer between two adjacent U-shaped grooves.

[0015] The beneficial effects of the present invention are:

[0016] The annular tooth roller screw proposed in the present invention has a multi-start external thread, the number of threads is N, and the rollers and nuts have annular convex teeth and concave teeth structures respectively; the rollers are distributed around the screw, the roller convex teeth are engaged with the screw threads, and the number of rollers R must satisfy R=N / Z, where Z is a positive integer, Z=1, 2, 3...; the installation interval angle of each roller in a group of rollers can be equal to Z×360° / N, where N is the number of screw heads, Z is a positive integer, Z=1, 2, 3.... This structure and parameter relationship can ensure that multiple rollers in the same group are in the same axial position, thereby meeting the requirement that the rollers are engaged with the nut and the screw at the same time. The beneficial effect of this structure is that the screw center diameter d s and roller median diameter d r There is no d between r =d s / (N-2) proportional relationship constraint, and the nut diameter d n and roller median diameter d r There is no d between n =Nd r The proportional relationship constraint is N, where N is the number of screw thread heads. The roller center diameter can be much smaller than the screw center diameter, and when the screw diameter is a constant, the radial size of the entire transmission mechanism is greatly reduced. In the present invention, the nut is an annular concave tooth structure, and there is no need to consider the problem of the inclination angle of the grinding wheel shaft during the grinding process. The processing difficulty of the nut will not increase with the increase in the number of screw thread heads. The selection of the number of screw thread heads does not need to consider the impact on the roller diameter, and a screw with a larger lead can be obtained, thereby improving the transmission speed and transmission efficiency of the transmission mechanism.

[0017] Furthermore, because both the roller and nut utilize annular teeth, there is no relative axial movement between the roller and nut, eliminating the need for specialized structures or devices to return the roller to its initial position. The parallel annular teeth of the roller and nut ensure that the theoretical meshing point of the two parts lies at the tangent point of the mid-diameter circle. This allows the roller to perform pure rolling motion within the nut, minimizing slippage between the roller and nut.

[0018] The present invention enables the assembly of multiple groups of rollers, allowing the long rollers in the original heavy-duty planetary roller screw to be decomposed into multiple short rollers for shared load bearing. The number of threads on a single roller can be reduced, and the design allows for different assembly clearances between each group of rollers, the screw, and the nut, allowing each group of rollers to bear the same load, thereby improving load-bearing capacity. The roller mean diameter of the present invention can be much smaller than the screw mean diameter, resolving the problem of severely uneven load distribution between the roller threads on the screw and nut sides caused by an overly large roller diameter (Blinov DS, Morozov MI. Uneven load distribution between mating windings of rollers and screws with nuts of planetary roller drives [J]. Science and Education of the Bauman MSTU, 2014, 9: 1-14).

[0019] In this invention, the rotation of the roller about its axis does not affect the relative axial position of the roller and nut, eliminating the need to consider phase matching between the roller and nut, or between the roller and the internal gear ring, during assembly. The rollers have contact sections of equal length on both the screw and nut sides, which improves the load-bearing capacity of the mechanism per unit axial length while protecting the rollers from excessive bending moment loads.

[0020] This invention significantly improves the thrust-to-weight ratio of heavy-duty planetary roller screws and reduces the radial dimensions of the transmission mechanism. This has far-reaching implications for promoting the replacement of high-thrust hydraulic and pneumatic servo systems with electromechanical servo systems, completely resolving the problems of "emission, bubbling, dripping, and leakage," improving the operating efficiency of mechanical equipment and reducing maintenance costs, promoting the rapid development of fully electrified intelligent equipment, and fostering a low-carbon, environmentally friendly economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a three-dimensional schematic diagram of the structure of an annular roller screw transmission mechanism;

[0022] Figure 2 It is a three-dimensional schematic diagram of the screw structure;

[0023] Figure 3 It is a three-dimensional schematic diagram of the roller structure;

[0024] Figure 4 It is a three-dimensional schematic diagram of the nut structure;

[0025] Figure 5 It is a planar schematic diagram of the nut structure;

[0026] Figure 6 It is a three-dimensional schematic diagram of the cage structure;

[0027] Figure 7 It is a three-dimensional schematic diagram of the inner gear ring structure;

[0028] Figure 8 It is a three-dimensional schematic diagram of the positioning pin structure;

[0029] Figure 9 It is a schematic cross-sectional diagram of the meshing of roller spur teeth and internal gear ring;

[0030] Figure 10 It is a schematic cross-sectional diagram of the engagement between the roller annular convex teeth, the nut annular concave teeth and the screw thread;

[0031] Figure 11 It is a three-dimensional schematic diagram of the structure of an annular roller screw transmission mechanism with one set of rollers;

[0032] Figure 12 It is a three-dimensional schematic diagram of the structure of an annular roller screw transmission mechanism with three groups of rollers. DETAILED DESCRIPTION

[0033] The present invention is further described below with reference to the accompanying drawings and examples. The present invention includes but is not limited to the following examples.

[0034] The present invention provides an annular roller screw transmission mechanism, comprising a screw, rollers, a nut, a retainer, an internal gear ring, and a locating pin. The screw has a multi-start external thread with a number of starts N and a pitch P. The rollers have multiple annular ridges, the spacing between the ridges equal to the screw pitch P, and straight teeth are machined at both ends of the ridges. The rollers are distributed around the screw, and the roller ridges mesh with the screw threads. The number of rollers, R, must satisfy R = N / Z, where Z is a positive integer, such as 1, 2, 3, etc. The screw has a pitch diameter d. s and roller median diameter d r There is no d between r =d s / (N-2) proportional relationship constraint; the nut has an annular concave tooth inside, and the nut has a groove inside that matches the cage and the inner gear ring; the annular concave tooth of the nut and the annular convex tooth of the roller are meshed with each other; since both the roller and the nut adopt an annular tooth design, the nut middle diameter d n and roller median diameter d r There is no d between n =Nd r The proportion relationship constraint; the retainer has a U-shaped groove and a cut-off opening; the inner gear ring is a thin-walled structural component with straight teeth, a positioning pin hole and a cut-off opening. The number of roller straight teeth is z r and the number of straight teeth on the nut z n Need to meet d r / d n =z r / z nThe inner ring gear elastically deforms to reduce its outer diameter, fits into the corresponding groove inside the nut, and then releases the elastic deformation to restore it to its original size. Subsequently, a locating pin is used to fix the installation phase angle of the inner ring gear. The retainer also elastically deforms to reduce its outer diameter, fits into the corresponding groove inside the nut, and then releases the elastic deformation to restore it to its original size.

[0035] Furthermore, a group of rollers with the same axial position around the screw is defined as one group. X groups can be installed in an annular roller screw, where X can be 1, 2, 3, etc. The long roller in the original heavy-duty planetary roller screw is decomposed into multiple short rollers to share the load.

[0036] Furthermore, when there are more than two groups of rollers, that is, when X≥2, each group of rollers can be designed to have different meshing clearances with the screw and nut according to the state of the external load on the nut and the screw, so that each group of rollers bears the same load.

[0037] Furthermore, the retainer can be processed with a process groove to improve its elastic deformation so as to reduce the outer diameter and fit into the nut.

[0038] Furthermore, the installation interval angle of each roller in a group of rollers can be equal to Z×360° / N, where N is the number of screw heads, Z is a positive integer, Z=1, 2, 3...

[0039] Furthermore, the roller's mean diameter can be much smaller than the screw's mean diameter; when the screw diameter is constant, the radial dimensions of the entire transmission mechanism are significantly reduced. The nut's annular concave tooth structure eliminates the need to consider the inclination angle of the grinding wheel axis during grinding.

[0040] like Figure 1 As shown, an embodiment of the present invention provides an annular roller screw transmission mechanism, including parts such as a screw 1, a roller 2, a nut 3, a retaining frame 4, an inner gear ring 5 and a positioning pin 6.

[0041] like Figure 2 As shown, in the embodiment of the present invention, the screw 1 is a multi-start thread, and the number of thread starts of the screw 1 in this embodiment is N s =20, the pitch is P=2mm, and the middle diameter of the screw 1 thread is 75mm.

[0042] like Figure 3 As shown, in the embodiment of the present invention, the middle section of the roller 2 is composed of a plurality of annular protrusions 2-3, the spacing between the annular protrusions 2-3 being equal to the screw pitch P = 2 mm; the ends of the roller 2 are optical axes 2-1; the optical axes 2-1 are matched with the U-shaped grooves 4-1 in the retainer 4; the ends of the annular protrusions 2-3 in the roller 2 are machined with roller spur teeth 2-2; the roller spur teeth 2-2 mesh with the inner ring spur teeth 5-1. In this embodiment, the number of teeth of the roller spur teeth 2-2 is z r=10, the pitch diameter of the roller annular tooth 2-3 is d r =10mm, the number of rollers in a group is N r =N s =20.

[0043] like Figure 4 and 5 As shown, in the embodiment of the present invention, the nut 3 has two sets of annular concave teeth 3-3, and the spacing between the annular concave teeth 3-3 is equal to the screw pitch P = 2mm; the interior of the nut 3 has an inner ring mounting groove 3-2 and a retainer mounting groove 3-1; a positioning pin through hole 3-4 is machined in the inner ring mounting groove 3-2; and a disassembly through hole 3-5 is machined in the retainer mounting groove 3-1. In this embodiment, the pitch diameter of the annular concave teeth 3-3 of the nut 3 is d n =95 mm. In this embodiment, the outer diameter of the nut 3 is 115 mm. In Rollvis products, when the screw diameter is 75 mm, the minimum outer diameter of the nut is 150 mm (Satellite roller screws [M]. Geneva: Rollvis, 2019, www.Rollvis.com).

[0044] like Figure 6 As shown, in the embodiment of the present invention, the retainer 4 has a plurality of evenly distributed U-shaped grooves 4 - 1 ; process grooves 4 - 2 are provided in the intervals between the U-shaped grooves 4 - 1 ; and there is a cut-off opening 4 - 3 in the retainer 4 .

[0045] like Figure 7 As shown, in the embodiment of the present invention, the inner gear ring 5 is a thin-walled structure, and the number of the inner gear ring straight teeth 5-1 in this embodiment is z n =z r / (d r / d n )=95; There is a positioning pin hole 5-2 on the inner ring gear 5, and a cut-off opening 5-3 is provided.

[0046] like Figure 8 As shown, in the embodiment of the present invention, the positioning pin 6 is in a stepped structure, wherein the large end 6-1 cooperates with the inner gear ring positioning pin hole 5-2, and the small end 6-2 cooperates with the nut positioning pin through hole 3-4.

[0047] In this embodiment, the four inner gear rings 5 ​​are first elastically deformed to reduce their outer diameters and inserted into the corresponding inner gear ring mounting grooves 3-2 within the nut 3. The elastic deformation is then released to restore them to their original size. Next, the positioning pins 6 are used to mate with the inner gear ring positioning pin holes 5-2 to fix the inner gear ring's installation phase angle. The four retaining frames 4 are elastically deformed to reduce their outer diameters and inserted into the corresponding retaining frame mounting grooves 3-1 within the nut 3. The elastic deformation is then released to restore them to their original size. Subsequently, the rollers 2 are installed so that the annular protruding teeth 2-3 of the rollers 2 mesh with the annular concave teeth 3-3 of the nut 3, the roller spur teeth 2-2 mesh with the inner gear ring spur teeth 5-1, and the optical axis 2-1 of the rollers 2 mates with the slots 4-3 in the retaining frame 4.

[0048] In this embodiment, a total of 2 groups of 40 rollers 2 are installed. Finally, the axis of the screw 1 is aligned with the axis of the nut 3, and the front end of the screw thread is in contact with the annular protrusion 2-3 of the roller 2. Then the screw is rotated and a certain axial pressure is applied to make the annular protrusion 2-3 of each roller 2 mesh with the screw thread. The annular tooth roller screw assembly is completed. The cross-sectional diagram of the meshing of the roller spur teeth 2-2 and the inner ring spur teeth 5-1 after assembly is shown as follows: Figure 9 The cross-sectional diagram of the meshing of the roller annular convex teeth 2-3, the nut annular concave teeth 3-3 and the screw 1 is shown in FIG. Figure 10 shown.

[0049] In this embodiment, the middle diameter of the screw 1 is 75 mm, and the outer diameter of the nut 3 is 115 mm. In the Rollvis product, the outer diameter of the nut corresponding to the 75 mm middle diameter of the screw is 150 mm.

[0050] The annular roller screw drive mechanism with 1 set and 3 sets of rollers can be assembled as follows Figure 11 and Figure 12 shown.

[0051] What is disclosed above is only a specific embodiment of the present invention. Those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. However, the embodiments of the present invention are not limited thereto. Any changes that can be conceived by those skilled in the art should fall within the scope of protection of the present invention.

Claims

1. An annular roller screw transmission mechanism, comprising a screw, a roller, a nut, a retaining frame, an inner gear ring and a positioning pin, characterized in that: The screw is a multi-start external thread with N number of threads and P pitch. The rollers have smooth axes at both ends and a plurality of annular convex teeth in the middle section. Straight teeth are machined circumferentially at both ends of the annular convex teeth. The spacing between the annular convex teeth is equal to the screw pitch P. The rollers are distributed around the screw, and the roller convex teeth are meshed with the screw threads. The number of rollers R must satisfy R=N / Z, where Z is a positive integer, Z=1, 2, 3...; the nut has annular concave teeth inside and a plurality of circumferential grooves are arranged along the axial direction; the annular concave teeth of the nut and the annular convex teeth of the rollers mesh with each other. The retaining frame is an annular structure with a cut-off opening, and the inner wall A plurality of U-shaped grooves are evenly distributed along the circumference; the inner gear ring is provided with an annular structure with a cutout, a plurality of spur teeth are evenly distributed along the circumference on the inner wall, and a radial locating pin hole is provided on the outer wall; the number of spur teeth zr of the roller and the number of spur teeth zn of the nut satisfy the ratio dr / dn=zr / zn, where dr and dn are the median diameters of the roller and nut, respectively; the inner gear ring is mounted in a groove on the inner wall of the nut, and the mounting phase angle of the inner gear ring is fixed using a locating pin, with the spur teeth of the inner gear ring meshing with the spur teeth of the roller; the retaining frame is mounted in a groove on the inner wall of the nut, and the optical axes at both ends of the roller match the U-shaped grooves of the retaining frame; A set of rollers with the same axial position around the screw is defined as one group. X groups are installed along the screw axial direction, where X = 1, 2, 3, etc. When there are more than two sets of rollers, the meshing clearance between each set of rollers and the screw and nut is designed to be different, depending on the external load conditions on the nut and screw, so that each set of rollers bears the same load.

2. The annular roller screw transmission mechanism according to claim 1, characterized in that: The installation spacing angle of each roller in a set of rollers is equal to Z×360° / N.

3. The annular roller screw transmission mechanism according to claim 1, characterized in that: The inner wall of the retainer is provided with a process groove between two adjacent U-shaped grooves.

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