roller screw mechanism

Abstract

This application relates to a roller screw mechanism comprising a main screw, at least three auxiliary screws, and a support frame. The main screw and auxiliary screws are housed in the support frame. Each auxiliary screw has at least one first segment and at least two second segments arranged alternately along the axial direction of the auxiliary screw. The radius of the first segment is larger than the radius of the second segment. The auxiliary screws are evenly distributed around the outer periphery of the main screw, and the external threads on the outer peripheral surface of the first segment engage with the external threads on the outer peripheral surface of the main screw. The support frame is constructed as a hollow cylinder, and its inner peripheral surface has at least one first region and at least two second regions arranged alternately along the axial direction of the support frame. The first region is constructed as a groove arranged along the inner peripheral surface, and the second region has recesses evenly distributed along the circumference of the support frame. The second segments of the auxiliary screws engage in the recesses, and the first segments are housed in the first region. The outer peripheral surface of the first segment is spaced apart from the inner peripheral surface of the support frame.

Description

Technical Field

[0001] This application relates to a lead screw drive mechanism, and more particularly to a roller lead screw mechanism. Background Technology

[0002] Screw drives are widely used mechanical transmission devices whose basic function is to convert rotary motion into linear motion, or vice versa. Depending on the transmission method, screw drives mainly include sliding screw mechanisms, ball screw mechanisms, and planetary roller screw mechanisms.

[0003] Planetary roller screw mechanisms are a further development of ball screw mechanisms. In planetary roller screw mechanisms, the balls are replaced by threaded rollers, which are arranged circumferentially between the screw and the nut. Driven by the screw, they rotate around their own axis (rotation) and revolve around the screw's axis (planetary motion). Because the rollers engage with the screw and nut via threads, the contact is formed by multiple helical lines simultaneously, resulting in a significantly larger contact area than the point contact of a ball screw. Therefore, planetary roller screw mechanisms have outstanding advantages such as high load-bearing capacity, good impact resistance, and long service life.

[0004] However, traditional planetary roller screw mechanisms also have a series of insurmountable technical problems, such as a large number of parts, complex structure, and difficulty in achieving large-scale mass production. Summary of the Invention

[0005] The technical problem to be solved by this application is to at least partially overcome the above-mentioned defects in the prior art and provide a roller screw mechanism that is simple in structure, easy to process and assemble, low in cost and has good load-bearing capacity.

[0006] One aspect of this application provides a roller screw mechanism comprising a main screw, at least three auxiliary screws, and a support frame. The main screw and the auxiliary screws are housed within the support frame. The outer circumferential surface of the main screw has a first external thread. Each auxiliary screw has at least one first segment and at least two second segments alternately arranged along the axial direction of the auxiliary screw. With reference to the central longitudinal axis of the auxiliary screw, the radius of the first segment is larger than the radius of the second segment. The outer circumferential surface of the first segment has a second external thread. The auxiliary screws are uniformly distributed circumferentially around the outer circumference of the main screw, and the second external threads engage with the first external threads. The support frame is constructed as a hollow cylinder, and its inner circumferential surface has at least one first region and at least two second regions alternately arranged along the axial direction of the support frame. The first region is constructed as a groove arranged on the inner circumferential surface. The second region has recesses uniformly distributed circumferentially along the support frame. The second section of the auxiliary lead screw engages in the recess, the first section of the auxiliary lead screw is housed in the first region, and the outer peripheral surface of the first section is spaced apart from the inner peripheral surface of the support frame.

[0007] According to one or more embodiments, the auxiliary lead screw has at least two first sections and at least three second sections arranged alternately along the axial direction of the auxiliary lead screw. By providing more first and second sections, the contact area and the number of mating points between the auxiliary lead screw and the support frame can be increased, thereby further improving the transmission capacity of axial and radial loads, enabling the mechanism to withstand greater loads.

[0008] According to one or more embodiments, the axial dimensions of the first sections of the auxiliary lead screws are identical to each other, and the axial dimensions of the second sections of the auxiliary lead screws are identical to each other. This design ensures good consistency and interchangeability among the auxiliary lead screws, reduces design and manufacturing costs, and ensures uniform and consistent fit between the auxiliary lead screws and the support frame. This facilitates even load distribution among the auxiliary lead screws and prevents premature failure of individual auxiliary lead screws due to uneven stress.

[0009] According to one or more embodiments, at least two first sections of the same auxiliary lead screw have different axial dimensions. This design allows for the allocation of differentiated load-bearing ratios based on the specific axial position of each first section.

[0010] According to one or more embodiments, two of the at least two second regions are respectively arranged at the axial ends of the support frame. This arrangement allows the support frame to provide radial support to the auxiliary lead screw at both axial ends through the second regions, thereby improving the support stiffness of the auxiliary lead screw in the support frame, preventing the auxiliary lead screw from deflecting under force, and ensuring the smoothness and accuracy of the transmission.

[0011] According to one or more embodiments, the first region of the support frame is constructed as an annular groove, the bottom surface of which is a continuous cylindrical surface. The continuous cylindrical surface structure is simple and easy to machine using conventional turning or milling processes, which helps reduce manufacturing costs.

[0012] According to one or more embodiments, the surface of the recess in the second region of the support frame is constructed as an arcuate surface that adapts to the outer peripheral surface of the second section of the auxiliary lead screw, and the depth of the recess is less than the radius of the second section of the auxiliary lead screw. The arcuate surface design allows the second section to fit well into the recess, facilitating the effective transmission of radial loads. While ensuring stable radial support for the second section of the auxiliary lead screw within the recess, it avoids excessive depth in the recess, which could cause the auxiliary lead screw to jam, thus ensuring smooth rotation of the auxiliary lead screw.

[0013] According to one or more embodiments, the axial length of the first region of the support frame is greater than the axial length of the first section of the auxiliary lead screw, thereby forming a gap between the axial side of the first section of the auxiliary lead screw and the axial sidewall of the first region of the support frame. On the one hand, this gap provides the necessary axial movement margin for the first section of the auxiliary lead screw, absorbing axial dimensional changes caused by machining errors and thermal expansion, and preventing jamming between the auxiliary lead screw and the support frame. On the other hand, this gap ensures that during axial load transmission, only one side of the first section of the auxiliary lead screw abuts against one sidewall of the first region of the support frame, avoiding unnecessary frictional losses between contact surfaces and improving transmission efficiency.

[0014] According to one or more embodiments, dustproof rubber seals are also provided at both ends of the support frame, and the dustproof rubber seals slide in contact with the outer peripheral surface of the main lead screw. The dustproof rubber seals can effectively prevent dust, moisture and other impurities in the external environment from entering the interior of the support frame, protecting the threaded meshing surfaces between the main lead screw and the auxiliary lead screw, as well as the mating surfaces between the auxiliary lead screw and the support frame, from contamination and wear, thereby significantly extending the service life of the mechanism and maintaining transmission accuracy.

[0015] According to one or more embodiments, the auxiliary lead screw and the support frame have the same axial dimension. This dimensional consistency allows the auxiliary lead screw and the support frame to be aligned axially, facilitating assembly and simplifying the design and installation of the seals at both ends, while improving the sealing effect through flush end faces.

[0016] According to one or more embodiments, the number of auxiliary lead screws is 4 to 8. Selecting 4 to 8 auxiliary lead screws achieves a good balance between transmission capacity and structural compactness. Too few auxiliary lead screws will result in excessive load on each individual lead screw, easily leading to excessive wear or fatigue failure; too many auxiliary lead screws will increase the radial dimension of the mechanism, which is not conducive to miniaturization design, and will also increase assembly difficulty and manufacturing costs. The design of 4 to 8 auxiliary lead screws can meet the load-bearing requirements of most application scenarios while maintaining a compact mechanism structure. Attached Figure Description

[0017] Figure 1 A partially sectional perspective view of the roller screw mechanism according to this application is shown;

[0018] Figure 2 A cross-sectional view of the roller screw mechanism according to this application is shown;

[0019] Figure 3 A partially sectional perspective view of the support frame of the roller screw mechanism according to this application is shown;

[0020] Figure 4 The individual support frame is shown in the sectional view;

[0021] Figure 5 The separate lead screw is shown in the sectional view;

[0022] Figure 6 The partial sectional perspective view shows the engagement of the auxiliary lead screw within the support frame;

[0023] Figure 7 Another embodiment of the support frame is shown in the sectional view;

[0024] Figure 8 The schematic stereoscopic view shows the relationship with Figure 7 The corresponding implementation method.

[0025] List of reference numerals

[0026] 1-Main lead screw; 2-Secondary lead screw; 21-First section; 211-Side of the first section; 22-Second section; 3-Support frame; 31-First area; 311-Bottom surface; 312-Side wall; 32-Second area; 321-Recess; 330, 340-Support frame sections; 4-Shell; 51-First end cap; 52-Second end cap; 61-Flange; 62-Longitudinal groove; 71-Sealing structure; x1-Central longitudinal axis of the main lead screw; x2-Central longitudinal axis of the secondary lead screw. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the described embodiments of this application without inventive effort are within the scope of protection of this application.

[0028] In this application, the term "axial" refers to the direction along the central longitudinal axis of the corresponding component (e.g., a main lead screw, auxiliary lead screw, or support frame). The term "radial" refers to the direction perpendicular to the central longitudinal axis of the corresponding component. The term "circumferential" refers to the circumferential direction around the central longitudinal axis of the corresponding component. The term "radius" refers to the radial distance from the central longitudinal axis of the component to the outer circumferential surface of the component. The term "axial dimension" refers to the axial length of a component or a portion thereof. The term "inner circumferential surface" refers to the inner circumferential surface of a hollow cylindrical component. These terms are used only for the convenience of describing this application and for simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting this application. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0029] Traditional planetary roller screw mechanisms, in addition to the screw, rollers, and nut, typically require synchronizing gear rings at both ends of the nut to ensure the rollers maintain the correct phase relationship as they revolve around the screw, preventing motion interference caused by relative rotation between rollers. Furthermore, cages are needed to constrain the axial position and circumferential distribution of the rollers. The presence of these additional components significantly increases the number of parts in the mechanism, increasing assembly difficulty and reducing reliability. Moreover, traditional planetary roller screw mechanisms require high precision in their components, making machining challenging. The threads on the screw, rollers, and nut must all have extremely high precision and surface quality; otherwise, transmission accuracy and service life will be affected. Machining the threads on the inner circumferential surface of the nut is particularly difficult because the nut is a ring-shaped part, and its internal threads require specialized internal thread grinding equipment, resulting in low efficiency and high cost. Furthermore, the machining of the synchronizing gear rings also requires high precision, further increasing manufacturing costs. Due to the high precision requirements and complex machining processes of these components, traditional planetary roller screw mechanisms rely primarily on high-precision specialized machining equipment and skilled technicians for production, resulting in low production efficiency and limited capacity. This directly leads to the high price of planetary roller screw mechanisms, making it difficult to meet the growing market demand, especially the large-scale mass production needs for high-performance screw drive mechanisms in emerging fields such as humanoid robots.

[0030] This application provides a roller screw mechanism comprising a main screw, at least three auxiliary screws, and a support frame. The main screw and the auxiliary screws are housed in the support frame. The outer circumferential surface of the main screw has a first external thread. Each auxiliary screw has at least one first segment and at least two second segments arranged alternately along the axial direction of the auxiliary screw. With reference to the central longitudinal axis of the auxiliary screw, the radius of the first segment is larger than the radius of the second segment. The outer circumferential surface of the first segment has a second external thread. The auxiliary screws are uniformly distributed circumferentially around the outer circumference of the main screw, and the second external threads engage with the first external threads. The support frame is constructed as a hollow cylinder, and its inner circumferential surface has at least one first region and at least two second regions arranged alternately along the axial direction of the support frame. The first region is constructed as a groove arranged radially along the inner circumferential surface of the support frame. The second regions have recesses uniformly distributed circumferentially along the support frame. The second segments of the auxiliary screws engage in the recesses, and the first segments of the auxiliary screws are housed in the first regions.

[0031] The main lead screw is capable of rotating around its own central longitudinal axis. Secondary lead screws are evenly distributed circumferentially along the main lead screw, and the second external thread on the first section of the secondary lead screw meshes with the first external thread on the main lead screw. When the main lead screw rotates, the threaded engagement drives each secondary lead screw to rotate synchronously around its respective central longitudinal axis. Since the second section of the secondary lead screw meshes in the recess of the second region of the support frame, while the first section of the secondary lead screw is accommodated in the first region of the support frame, the secondary lead screw transmits the driving force applied by the main lead screw to the support frame through the shape fit between its first section and the first region, and the shape fit between its second section and the recess, thereby driving the support frame to move linearly along the axial direction of the main lead screw.

[0032] The ball screw mechanism of this application eliminates the complex and difficult-to-machine internally threaded nut found in traditional planetary ball screw mechanisms, replacing it with a support frame having specific grooves and recesses. This support frame can form a form fit with the first and second sections of the auxiliary screw through first and second regions on its inner circumferential surface, respectively, thereby enabling the transmission of axial and radial loads. This design fundamentally simplifies the mechanism's structure and reduces the difficulty of machining the parts.

[0033] In the roller screw mechanism according to this application, the auxiliary screw no longer performs planetary motion (i.e., revolution) around the main screw, but only rotates around its own central longitudinal axis. This eliminates the need for a synchronous gear ring, significantly reduces the number of parts, simplifies the assembly process, and improves the reliability and compactness of the mechanism.

[0034] The ball screw mechanism according to this application can achieve load-bearing capacity and transmission accuracy comparable to traditional planetary ball screw mechanisms, while significantly reducing manufacturing costs and making it suitable for large-scale mass production. This effectively solves the problems of production capacity bottleneck and high cost in the prior art for planetary ball screw mechanisms.

[0035] The following combination Figures 1 to 6 The present application provides a detailed description of the roller screw mechanism and its various components.

[0036] Figure 1 A partially sectional perspective view of the roller screw mechanism according to this application is shown. Figure 1 As shown, the roller screw mechanism generally includes a main screw 1, multiple auxiliary screws 2, and a support frame 3. Both the main screw 1 and the auxiliary screws 2 are housed inside the support frame 3. The main screw 1 extends along the central longitudinal axis of the support frame 3, passing through the internal space of the support frame 3. The multiple auxiliary screws 2 are arranged around the outer periphery of the main screw 1 and are evenly distributed along the circumference of the main screw 1. A first external thread is provided on the outer circumferential surface of the main screw 1. At least a portion of the outer circumferential surface of the auxiliary screws 2 is provided with a second external thread, which engages with the first external thread of the main screw 1.

[0037] The auxiliary lead screw 2 is constructed having multiple segments arranged alternately along its axial direction. Specifically, the auxiliary lead screw 2 has at least one first segment 21 and at least two second segments 22. In this application, the first segment 21 and the second segment 22 are defined relative to the radial dimension of the auxiliary lead screw 2. With reference to the central longitudinal axis x2 of the auxiliary lead screw 2, the radius of the first segment 21 is larger than the radius of the second segment 22. In other words, the first segment 21 is a radially outward protruding segment on the auxiliary lead screw 2, while the second segment 22 is a radially inward recessed segment on the auxiliary lead screw 2 relative to the first segment 21. The aforementioned second external thread is provided on the outer circumferential surface of the first segment 21. Since the radius of the first segment 21 is larger than the radius of the second segment 22, the second external thread is provided on the outer circumferential surface of the first segment 21 such that the thread pitch diameter of the second external thread matches the thread root diameter of the first external thread of the main lead screw 1, thereby achieving thread engagement.

[0038] The auxiliary lead screw 2 is evenly distributed around the outer periphery of the main lead screw 1 along the circumference. Figure 1The illustrated embodiment shows three auxiliary lead screws 2 evenly arranged around the main lead screw 1. It is understood that the number of auxiliary lead screws 2 is not limited to three, but can be four, five, six, seven, eight, or more, depending on specific load requirements and space constraints. Preferably, the number of auxiliary lead screws 2 is four to eight. The threaded engagement between the auxiliary lead screws 2 and the main lead screw 1 ensures that when the main lead screw 1 rotates around its central longitudinal axis, each auxiliary lead screw 2 can be synchronously driven to rotate around its respective central longitudinal axis x2. Since each auxiliary lead screw 2 engages with the main lead screw 1 and is evenly distributed, the rotational motion of the main lead screw 1 is simultaneously transmitted to all auxiliary lead screws 2, causing all auxiliary lead screws 2 to rotate synchronously.

[0039] The support frame 3 is constructed as a hollow cylindrical structure. The support frame 3 has an inner circumferential surface and an outer circumferential surface. Both the main lead screw 1 and the auxiliary lead screw 2 are housed within the internal space enclosed by the inner circumferential surface of the support frame 3. At least one first region 31 and at least two second regions 32 are alternately arranged along the axial direction of the support frame 3 on the inner circumferential surface. The first region 31 is constructed as a groove recessed radially inward along the support frame 3. That is, the first region 31 is a region radially outward recessed on the inner circumferential surface of the support frame 3. The second region 32 is a region on the inner circumferential surface of the support frame 3 without a groove, and its inner diameter is smaller than the diameter of the bottom surface of the first region 31. Each second region 32 has recesses 321 evenly distributed along the circumference of the support frame 3. The recesses 321 are dimples formed by further radially outward recessing on the inner circumferential surface of the second region 32.

[0040] The second section 22 of the auxiliary lead screw 2 engages in the recess 321 of the second region 32. Specifically, the outer peripheral surface of the second section 22 of the auxiliary lead screw 2 forms a form fit with the surface of the recess 321, thereby positioning the auxiliary lead screw 2 in the support frame 3 and allowing the radial load of the auxiliary lead screw 2 to be transmitted to the support frame 3 through this fit. The first section 21 of the auxiliary lead screw 2 is accommodated in the first region 31. Since the first region 31 is constructed as a groove, the first section 21, as a radially protruding part of the auxiliary lead screw 2, can be accommodated in the groove, such that the outer peripheral surface of the first section 21 is spaced apart from the first region, and the axial end face of the first section 21 can abut against the side wall of the first region 31, thereby realizing the transmission of axial load.

[0041] During operation, the main lead screw 1 rotates around its central longitudinal axis x1 under the drive of an external driving source (such as an electric motor). Through the engagement between the first external thread of the main lead screw 1 and the second external thread of the first section 21 of the auxiliary lead screw 2, the rotational motion of the main lead screw 1 drives each auxiliary lead screw 2 to rotate synchronously around its respective central longitudinal axis x2. The rotational motion of the auxiliary lead screw 2 is converted into linear motion of the support frame 3 along the axial direction of the main lead screw 1 through the engagement between its second section 22 and the recess 321 of the second region 32 of the support frame 3, and the engagement between its first section 21 and the first region 31.

[0042] Unlike traditional planetary roller screw mechanisms, in the roller screw mechanism of this application, the auxiliary screw 2 does not undergo planetary motion (i.e., revolution) around the main screw 1. Each auxiliary screw 2 only rotates around its own axis, and the position of its central longitudinal axis x2 relative to the main screw 1 is fixed. This feature eliminates the need for complex components such as synchronous gear rings and cages required in traditional planetary roller screw mechanisms. The position and movement of the auxiliary screw 2 are constrained and guided by the first region 31 and the second region 32 in the support frame 3.

[0043] Figure 2 A cross-sectional view of a roller screw mechanism according to this application is shown. Figure 2 The cutting plane passes through the central longitudinal axis x1 of the main lead screw 1 and the central longitudinal axis x2 of two of the auxiliary lead screws 2. From Figure 2 The relative positions and coordination between the main lead screw 1, the auxiliary lead screw 2, and the support frame 3 can be seen more clearly in the image.

[0044] like Figure 2 As shown, the main lead screw 1 extends along its central longitudinal axis x1. A first external thread is provided on the outer circumferential surface of the main lead screw 1. The first external thread can be a trapezoidal thread, a rectangular thread, or a sawtooth thread, etc., suitable for transmitting large loads. Preferably, the first external thread is a trapezoidal thread, which has high load-bearing capacity and good machinability.

[0045] The auxiliary lead screw 2 is arranged around the main lead screw 1. Figure 2 In the cross-sectional view shown, it can be clearly seen that the auxiliary lead screw 2 has a plurality of first sections 21 and a plurality of second sections 22 arranged alternately along its axial direction. In the illustrated embodiment, the auxiliary lead screw 2 has six first sections 21 and five second sections 22. The first sections 21 and 22 are arranged alternately along the axial direction of the auxiliary lead screw 2. A second external thread is provided on the outer circumferential surface of the first section 21. The second external thread engages with the first external thread on the main lead screw 1.

[0046] In one or more embodiments, the auxiliary lead screw 2 and the support frame 3 have the same axial dimension. This aligns the two axial ends of the auxiliary lead screw 2 with the two axial ends of the support frame 3, thereby maximizing the use of the axial length of the support frame 3 to support the auxiliary lead screw 2 and improving the overall rigidity and compactness of the mechanism.

[0047] Figure 3 A partially sectional perspective view of the support frame of the roller screw mechanism according to this application is shown. Figure 4 The individual support frame is shown in the sectional view. Figure 3 and Figure 4 The main lead screw and auxiliary lead screw are omitted; only the support frame 3 itself is shown. From Figure 3 and Figure 4 The specific structure of the first region 31 and the second region 32 set on the inner circumference surface of the support frame 3 can be seen more clearly in the image.

[0048] like Figure 3 As shown, the support frame 3 is a hollow cylindrical component. Along the axial direction of the support frame 3, a first region 31 and a second region 32 are arranged alternately. The first region 31 is an annular groove that is radially recessed outward on the inner circumferential surface of the support frame 3. In the illustrated embodiment, the bottom surface 311 of the annular groove is a smooth cylindrical surface. (Combined with...) Figure 3 , Figure 4 The first region 31 also has a sidewall 312 that separates the first region 31 from the adjacent second region 32. The sidewall 312 is preferably inclined relative to the cross-section of the support frame 3. Specifically, the sidewall 312 may be inclined at a certain angle relative to the radial direction of the support frame 3, so that the first region 31 has a gradually increasing axial width in the radially inward direction. This inclined arrangement facilitates a good fit between the side surface 211 of the first section 21 of the auxiliary lead screw 2 and the sidewall 312 (see...). Figure 6 This is beneficial for the uniform distribution of axial load.

[0049] The second region 32 is an annular region on the inner circumferential surface of the support frame 3 without grooves. Multiple recesses 321 are evenly distributed circumferentially within the second region 32. The recesses 321 are further recessed radially outward on the inner circumferential surface of the second region 32. The number of recesses 321 in each second region is the same as the number of auxiliary lead screws 2. For example, in an embodiment with three auxiliary lead screws 2, each second region 32 has three corresponding recesses 321, evenly distributed at 120° intervals along the circumferential direction of the support frame 3. The surface of the recesses 321 is an arcuate surface adapted to the outer circumferential surface of the second segment 22 of the auxiliary lead screw 2. The axial dimension of the recesses 321 is adapted to the axial dimension of the second segment 22 of the auxiliary lead screw 2, allowing the second segment 22 to be accurately embedded in the recesses 321.

[0050] The second region 32, in the portion between two adjacent recesses 321, forms a support portion that supports the second segment 22 of the auxiliary lead screw 2 in the circumferential direction, preventing the auxiliary lead screw 2 from moving in the circumferential direction. This structure ensures that each second segment 22 of each auxiliary lead screw 2 is positioned and supported by a corresponding recess 321, thereby guaranteeing that the relative positional relationship between the auxiliary lead screws 2 remains unchanged.

[0051] In one or more embodiments, the depth of the recess 321 in the second region 32 of the support frame 3 is designed to be less than the radius of the second segment 22 of the auxiliary lead screw 2. This means that when the second segment 22 engages in the recess 321, most of the radial portion of the second segment 22 is still exposed in the internal space of the support frame 3, thereby ensuring that the second segment 22 of the auxiliary lead screw 2 obtains stable radial support in the recess 321 while avoiding the auxiliary lead screw from getting stuck due to an excessively deep recess, thus ensuring the smooth rotation of the auxiliary lead screw.

[0052] Figure 5 The separate lead screw 2 is shown in the sectional view. Figure 5 The cutting plane passes through the central longitudinal axis x2 of the auxiliary lead screw 2. From Figure 5 The alternating arrangement of the first section 21 and the second section 22 of the auxiliary lead screw 2 can be clearly seen in the image.

[0053] In one or more embodiments, the auxiliary lead screw 2 is generally an elongated rod-shaped member. The auxiliary lead screw 2 has a plurality of first segments 21 and a plurality of second segments 22 arranged alternately along its axial direction. The outer diameter of the first segments 21 is larger than the outer diameter of the second segments 22. The axial dimensions of the first segments 21 and the second segments 22 can be selected according to specific load requirements and design parameters. Since the second external thread is only provided on the first segments 21, and the number and axial length of the first segments 21 can be selected according to design requirements, this significantly shortens the thread processing length and reduces processing difficulty and cost compared to the full-length thread design of traditional rollers. In one or more embodiments, the axial dimensions of the first segments 21 of the auxiliary lead screw 2 are the same as each other, and the axial dimensions of the second segments 22 of the auxiliary lead screw 2 are also the same as each other. This design makes the auxiliary lead screw 2 exhibit a regular periodic structure in the axial direction, which is beneficial for the uniform distribution of load in the axial direction and also facilitates processing and inspection. In one or more embodiments, the axial lengths of the various first segments 21 of the same auxiliary lead screw 2 can be designed differently from each other, and correspondingly, the axial lengths of the first regions 31 in the support frame 3 are also designed differently. Specifically, for example, in a design with at least three first segments 21, the first segment 21 located in the middle region can be provided with a larger axial dimension to bear the main thrust, while the first segment 21 near the end is provided with a smaller axial dimension to focus on guiding and limiting functions, thereby achieving a better distribution of axial load and improving the overall load-bearing efficiency and service life of the mechanism.

[0054] A second external thread is provided on the outer peripheral surface of the first segment 21. The second external thread extends along the entire outer peripheral surface of the first segment 21. Between two adjacent first segments 21 is a second segment 22, the outer peripheral surface of which is preferably a smooth cylindrical surface.

[0055] Preferably, both axial ends of the auxiliary lead screw 2 are the second section 22. This allows both axial ends of the auxiliary lead screw 2 to be supported by the second region 32 of the support frame 3 located at the axial ends, which helps to improve the support stiffness of the auxiliary lead screw 2.

[0056] Figure 6 The partially sectional perspective view shows the engagement of the auxiliary lead screw within the support frame. Figure 6 The fit between the first section 21 of the auxiliary lead screw 2 and the first region 31 of the support frame 3 can be clearly seen, as well as the fit between the second section 22 of the auxiliary lead screw 2 and the recess 321 of the second region 32 of the support frame 3.

[0057] like Figure 6 As shown, the auxiliary lead screw 2 is arranged inside the support frame 3 along the axial direction of the support frame 3. The first section 21 of the auxiliary lead screw 2 is housed in the first region 31 of the support frame 3. The side 211 of the first section 21 abuts against the side wall 312 of the first region 31. This abutting relationship allows the radial force generated by the rotation of the auxiliary lead screw 2 when the main lead screw 1 drives the auxiliary lead screw 2 to rotate through threaded engagement, which can be transmitted from the auxiliary lead screw 2 to the support frame 3 through the fit between the second section 22 and the recess 321, thereby realizing the linear movement of the support frame 3. At the same time, the fit between the second section 22 and the recess 321 also serves to constrain the circumferential position of the auxiliary lead screw 2, preventing the auxiliary lead screw 2 from shifting circumferentially.

[0058] In one or more embodiments, the axial length of the first region 31 of the support frame 3 is greater than the axial length of the first segment 21 of the auxiliary lead screw 2. For example... Figure 6 As shown, a gap is formed between the axial side surface 211 of the first segment 21 and the axial end face, i.e., the side wall 312, of the first region 31. This gap serves multiple purposes. First, it allows the first segment 21 of the auxiliary lead screw 2 to have a small allowance of movement in the axial direction, thereby absorbing dimensional changes caused by machining errors and thermal deformation, and preventing jamming. On the other hand, this gap ensures that during axial load transmission, only one side surface of the first segment of the auxiliary lead screw abuts against one side wall of the first region of the support frame, avoiding unnecessary frictional losses between contact surfaces and improving transmission efficiency. In one or more embodiments, the axial length of the first region 31 is 0.05 mm to 0.5 mm greater than the axial length of the first segment 21.

[0059] In one or more embodiments, two of the at least two second regions 32 of the support frame 3 are respectively arranged at the axial ends of the support frame 3. In other words, both axial ends of the support frame 3 are second regions 32. This arrangement allows the auxiliary lead screw 2 to receive radial support at both axial ends, thereby improving the support stiffness of the auxiliary lead screw 2 and preventing the auxiliary lead screw 2 from bending and deforming under stress.

[0060] In one or more embodiments, dustproof rubber seals are also provided at both ends of the support frame 3. These dustproof rubber seals can be constructed as annular sealing rings, for example, located at the axial ends of the support frame 3 and slidingly contacting the outer circumferential surface of the main lead screw 1. The function of the dustproof rubber seals is to prevent dust, moisture, and other impurities from the external environment from entering the mechanism through the end openings of the support frame 3. Since the threaded meshing surfaces between the main lead screw 1 and the auxiliary lead screw 2, as well as the mating surfaces between the auxiliary lead screw 2 and the support frame 3, are all precision mating surfaces, the entry of foreign objects may lead to accelerated wear, decreased transmission accuracy, or even mechanism jamming. The dustproof rubber seals effectively solve this problem and significantly extend the service life of the mechanism.

[0061] The dustproof rubber seal is preferably made of a rubber material with good wear resistance and appropriate elasticity, such as nitrile rubber (NBR), fluororubber (FKM), or silicone rubber (VMQ). The contact pressure between the seal and the main screw 1 should be moderate, ensuring a good sealing effect without generating excessive frictional resistance, so as not to affect the transmission efficiency.

[0062] like Figure 7 As shown, in one or more embodiments, the support frame 3 is composed of at least two support frame segments 330, 340 sequentially arranged along the axial direction. Each support frame segment 330, 340 has at least one first region 31 or at least one second region 32. Figure 7In the example shown, each support frame segment 330, 340 simultaneously has a first region 31 and a second region 32. Multiple support frame segments 330, 340 are arranged alternately along the axial direction and sequentially spliced ​​together to form a complete support frame 3, with the first region 31 and the second region 32 alternately distributed on its inner circumferential surface. Adjacent support frame segments can be fixedly connected by end face fitting, for example by locating pins, key connections, or welding, or they can be held axially abutting by a housing, as will be described below. This segmented structure of the support frame allows for the machining of only a small number of the first or second regions for each support frame segment, or even only a single type of profile, i.e., machining only the first or second region. It eliminates the need for alternating machining of different structures inside the deep hole, enabling efficient completion using conventional turning, milling, or broaching equipment. This significantly reduces reliance on specialized deep-hole machining equipment, shortens the machining cycle, and lowers manufacturing costs. Furthermore, by selecting and combining different numbers of sections, the total axial length of the support frame 3 and the distribution pattern of the first region 31 and the second region 32 can be flexibly adjusted to adapt to different stroke and load requirements without redesigning the overall blank or mold. When individual sections are worn or damaged, those sections can be replaced individually without scrapping the entire support frame, significantly improving maintainability.

[0063] like Figure 8 As shown, in the embodiment employing a segmented support frame, the roller screw mechanism preferably also has a housing 4 that surrounds the support frame 3 circumferentially. The housing 4 is constructed as a hollow sleeve, with its inner diameter matching the outer diameter of the support frame 3, and is fitted onto the outer circumferential surface of the support frame 3. Flanges 61 or longitudinal grooves 62 extending longitudinally along the support frame 3 are respectively provided on the outer circumferential surface of each support frame segment, while longitudinal grooves 62 or flanges 61 are correspondingly provided on the inner circumferential surface of the housing 4 facing the support frame, and the two are interlocked. Specifically, multiple longitudinal flanges 61 can be evenly distributed circumferentially on the outer circumferential surface of each support frame segment, while the same number and matching size of longitudinal grooves 62 can be provided at corresponding positions on the inner circumferential surface of the housing 4; conversely, longitudinal grooves 62 can be provided on the outer circumferential surface of the support frame segment, and flanges 61 can be provided on the inner circumferential surface of the housing 4.

[0064] The engagement of flange 61 and longitudinal groove 62 reliably locks the support frame section in the circumferential direction, preventing it from rotating relative to the housing 4. This ensures that the recess 321 in the second region 32 and the auxiliary lead screw 2 remain accurately aligned in the circumferential direction, guaranteeing that the auxiliary lead screw 2 can smoothly engage in the recess 321 and preventing motion interference or uneven load distribution caused by circumferential offset. Furthermore, this engagement structure connects multiple independent support frame sections axially and constrains them into a whole, preventing relative rotation or radial misalignment between sections without additional fasteners, thus simplifying the assembly process.

[0065] Furthermore, a first end cap 51 and a second end cap 52 may be respectively provided at both ends of the housing 4. The first end cap 51 and the second end cap 52 are fixed to the axial ends of the housing 4 by means of threaded connection, and clamp the axial ends of the support frame 3 between them, thereby limiting the axial position of the support frame 3 within the housing 4 and preventing the support frame section from moving axially. The center of the first end cap 51 and the second end cap 52 is provided with a through hole for the main lead screw 1 to pass through. Preferably, the inner surfaces of the first end cap 51 and the second end cap 52 are also provided with an elastic sealing structure 71. This elastic sealing structure can be constructed as an annular sealing ring, which serves to seal the internal space of the support frame 3 on the one hand, and to absorb axial impact and compensate for dimensional changes caused by thermal expansion on the other hand.

[0066] The working process of the roller screw mechanism of this application is described in detail below.

[0067] The basic working mode of the roller screw mechanism in this application is to convert the rotational motion of the main screw 1 into the linear motion of the support frame 3.

[0068] When the main lead screw 1 rotates around its central longitudinal axis under the drive of an external rotary drive source (such as an electric motor, hydraulic motor, or manual crank), the first external thread on the main lead screw 1 rotates accordingly. Since the second external thread on the first section 21 of the auxiliary lead screw 2 meshes with the first external thread of the main lead screw 1, the rotational motion of the main lead screw 1 is transmitted to each auxiliary lead screw 2 through the thread meshing action. Specifically, each auxiliary lead screw 2 is driven to rotate synchronously (rotate) around its respective central longitudinal axis x2.

[0069] Because the second section 22 of the auxiliary lead screw 2 engages in the recess 321 of the second region 32 of the support frame 3, the auxiliary lead screw 2 is fixed in the circumferential direction relative to the support frame 3 (i.e., it cannot revolve around the main lead screw 1), and can only rotate around its own central longitudinal axis x2. At the same time, the first section 21 of the auxiliary lead screw 2 is accommodated in the first region 31 of the support frame 3, and the side 211 of the first section 21 abuts against the side wall 312 of the first region 31, so that the auxiliary lead screw 2 and the support frame 3 are relatively fixed in the axial direction.

[0070] As the auxiliary lead screw 2 rotates, since it is axially fixed relative to the support frame 3, and the first external thread on the main lead screw 1 is a helical structure, the auxiliary lead screw 2 will move axially relative to the main lead screw 1 during its rotation. Because the auxiliary lead screw 2 engages with the support frame 3 through its first region 31 and second region 32, the axial movement of the auxiliary lead screw 2 is forcibly transmitted to the support frame 3, thereby driving the support frame 3 to move linearly along the axial direction of the main lead screw 1.

[0071] When the rotation direction of the main screw 1 changes, the linear motion direction of the support frame 3 also changes, thus achieving reciprocating linear motion.

[0072] Compared to traditional planetary roller screw mechanisms, the roller screw mechanism of this application differs fundamentally in its working principle. In traditional planetary roller screw mechanisms, the rollers revolve around the screw while simultaneously rotating on their own axes, meaning the rollers participate in two motions at the same time. To maintain the correct phase relationship between the rollers, synchronous gear rings must be provided at both ends of the nut. However, in the mechanism of this application, the auxiliary screw 2 only rotates on its own axis, and the position of its central longitudinal axis x2 relative to the main screw 1 remains constant. This kinematic simplification provides a basis for structural simplification of the mechanism, allowing complex parts such as synchronous gear rings and cages to be omitted.

[0073] The exemplary implementation of the proposed solution in this application has been described in detail above with reference to preferred embodiments. However, those skilled in the art will understand that various modifications and alterations can be made to the above specific embodiments without departing from the spirit of this application, and various combinations can be made to the various technical features and structures proposed in this application without exceeding the protection scope of this application, which is determined by the appended claims.

Claims

1. A roller screw mechanism, comprising: Main lead screw (1), At least three auxiliary lead screws (2), and The support frame (3) houses the main lead screw (1) and the auxiliary lead screw (2). in, The outer circumferential surface of the main lead screw (1) has a first external thread. The auxiliary lead screw (2) is characterized in that it has at least one first section (21) and at least two second sections (22) arranged alternately along the axial direction of the auxiliary lead screw (2). With reference to the central longitudinal axis (x2) of the auxiliary lead screw (2), the radius of the first section (21) is greater than the radius of the second section (22). The outer circumferential surface of the first section (21) has a second external thread. The auxiliary lead screw (2) is uniformly distributed circumferentially around the outer circumference of the main lead screw (1), and the second external thread meshes with the first external thread. The support frame is constructed as a hollow cylinder, and its inner circumferential surface has at least one first region (31) and at least two second regions (32) arranged alternately along the axial direction of the support frame. The first region (31) is constructed as a groove arranged on the inner circumferential surface. The second region (32) has recesses (321) evenly distributed along the circumference of the support frame (3). The second section (22) of the auxiliary lead screw (2) engages in the recesses (321). The first section (21) of the auxiliary lead screw (2) is accommodated in the first region (31), and the outer circumferential surface of the first section (21) is spaced apart from the inner circumferential surface of the support frame.

2. The roller screw mechanism according to claim 1, characterized in that, The auxiliary lead screw has at least two first sections (21) and at least three second sections (22) arranged alternately along the axial direction of the auxiliary lead screw.

3. The roller screw mechanism according to claim 1 or 2, characterized in that, The axial dimensions of the first section (21) of the auxiliary lead screw (2) are the same as each other, and the axial dimensions of the second section (22) of the auxiliary lead screw are the same as each other.

4. The roller screw mechanism according to claim 2, characterized in that, The axial dimensions of at least two first sections (21) of the same auxiliary lead screw (2) are different from each other.

5. The roller screw mechanism according to claim 1 or 2, characterized in that, Two of the at least two second regions (32) are respectively arranged at the axial ends of the support frame (3).

6. The roller screw mechanism according to claim 1 or 2, characterized in that, The first region (31) of the support frame (3) is constructed as an annular groove, and the bottom surface (311) of the groove is a continuous cylindrical surface.

7. The roller screw mechanism according to claim 1 or 2, characterized in that, The surface of the recess (321) of the second region (32) of the support frame is configured as an arc surface that matches the outer peripheral surface of the second section (22) of the auxiliary lead screw (2), and the depth of the recess (321) is less than the radius of the second section (22) of the auxiliary lead screw (2).

8. The roller screw mechanism according to claim 1 or 2, characterized in that, The axial length of the first region (31) of the support frame (3) is greater than the axial length of the first section (21) of the auxiliary lead screw (2), thereby forming a gap between the axial end face of the first section of the auxiliary lead screw (2) and the axial end face of the first region of the support frame (3).

9. The roller screw mechanism according to claim 1 or 2, characterized in that, The support frame (3) is also provided with dustproof rubber seals at both ends, and the dustproof rubber seals slide in contact with the outer peripheral surface of the main screw (1).

10. The roller screw mechanism according to claim 1 or 2, characterized in that, The auxiliary lead screw (2) and the support frame (3) have the same axial dimension.

11. The roller screw mechanism according to claim 1 or 2, characterized in that, The number of auxiliary lead screws (2) is 4 to 8.

12. The roller screw mechanism according to claim 1 or 2, characterized in that, The support frame (3) is composed of at least two support frame sections that are sequentially arranged along the axial direction, wherein each support frame section has at least one first region (31) or at least one second region (32).

13. The roller screw mechanism according to claim 12, characterized in that, The roller screw mechanism has a housing (4) surrounding the support frame (3) circumferentially outside the support frame (3), wherein the outer peripheral surface of the support frame section has a flange or longitudinal groove extending along the longitudinal direction of the support frame, and the inner peripheral surface of the housing facing the support frame has a corresponding longitudinal groove or flange.

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