Planetary roller screw

Abstract

A planetary roller screw is used for solving the problem that an existing planetary roller screw is insufficient in structural strength. Comprising a main screw provided with a first external thread, a nut provided with an internal thread, a planetary set provided with a plurality of rollers, and each roller is provided with a second external thread; the spiral directions of the first external thread and the internal thread are opposite, and the spiral directions of the internal thread and the second external thread are the same; based on the fact that the ratio of pitch diameters between the driven parts is the same as the ratio of the spiral line number, the spiral line number of the nut is not equal to the sum of the spiral line number of the main screw and the spiral line number of the two rollers; when the driving part is rotated, the driving part generates relative displacement on the driven parts in the axial direction, and the driven parts do not generate relative displacement in the axial direction. According to the invention, motion precision can be maintained and structural strength can be improved.

Description

Technical Field

[0001] This invention relates to a linear translation technique, and more particularly to a planetary roller screw. Background Technology

[0002] With the development of industrial technology, especially in the development of electric vehicles and humanoid robots, the use of planetary roller screws for linear translational motion control has the characteristics of being able to withstand high loads, high positioning accuracy, and fast movement speed, and can replace traditional hydraulic mechanisms.

[0003] Please refer to Figure 1 The present invention is a planetary roller screw 9, which consists of a main screw 91 and a nut 92 with several rollers 93 disposed between them. The main screw 91 has a first external thread 911 and the nut 92 has an internal thread 921. The several rollers 93 are identical to each other to form a planetary set, and each of the several rollers 93 has a second external thread 931. The main screw 91 is the driving member and rotates, so that the rollers 93 and the nut 92 move integrally along the axial direction of the main screw 91.

[0004] Based on the existing motion mechanism of the planetary roller screw 9, the main screw 91 or the nut 92 to be rotated is defined as the driving element, and the other of the main screw 91 or the nut 92 that produces linear movement is defined as the driven element. When the main screw 91, the nut 92, and the rollers 93 have a large pitch, the linear movement of the driven element caused by one rotation of the driving element is large, resulting in a high linear movement speed, and each component has a large load-bearing / pressure-bearing capacity. When the main screw 91, the nut 92, and the rollers 93 have a small pitch, the linear movement of the driven element caused by one rotation of the driving element is small, resulting in a low linear movement speed, but the movement can be precisely controlled. However, the load-bearing capacity of each component also decreases as the pitch decreases. Therefore, for applications in electric vehicles and humanoid robots, the existing planetary roller screw 9 cannot simultaneously achieve both precise control of movement and a large load-bearing capacity.

[0005] In addition, a prior art discloses a design rule that limits the number of spiral lines T of the main screw 91. 91 It must be: the number of helixes T93 of roller 93 multiplied by the pitch circle diameter D91 of main screw 91, divided by the pitch circle diameter D of roller 93. 93 That is, the corresponding formula can be expressed as T. 91 = T 93 (D 91 / D 93 ); and simultaneously limit the number of helixes T of nut 92. 92 Must be: the number of helixes T of the main screw 91 91 Add two rollers with a spiral line count of 93 T93 That is, the corresponding formula can be expressed as T. 92 = T 91 + 2T 93 .

[0006] In particular, among the constraints proposed in the aforementioned design rules, based on the pitch circle diameter D of nut 92 92 It must be equal to the pitch circle diameter D of the main screw 91. 91 Add the pitch circle diameter D of the two rollers 93 93 That is, the corresponding formula can be defined as D. 92 = D 91 + 2D 93 Therefore, the existing dimensional specifications can be derived as follows: [the pitch circle diameter D of the main screw 91] 91 With the pitch circle diameter D of roller 93 93 The ratio of [the number of helixes T of the main screw 91] is equal to [the number of helixes T]. 91 The number of spiral lines T of roller 93 93 The ratio of [ ], and the number of helixes T of nut 92 92 The number of helixes T equals the number of threads on the main screw 91. 91 Add two rollers with a spiral line count of 93 T 93 That is, the corresponding formula can be expressed as D. 91 / D 93 = T 91 / T 93 And T 92 = T 91 +2T 93 .

[0007] However, in the actual process of rotating a driving member, the planetary roller screw 9 manufactured according to the above design rules is prone to slippage / slippage between the main screw 91, roller 93 and nut 92, and cannot effectively produce the expected rotation to output stroke ratio.

[0008] In view of this, there is indeed a need to improve the existing planetary roller screw. Summary of the Invention

[0009] To address the aforementioned problems, the present invention aims to provide a planetary roller screw that can significantly improve motion accuracy without reducing the load-bearing pressure.

[0010] A secondary objective of this invention is to provide a planetary roller screw that enables smooth motion control.

[0011] The directions or approximate terms used throughout this invention, such as "front," "rear," "left," "right," "top," "bottom," "inner," "outer," "side," "axial," and "radial," are primarily for reference to the directions in the accompanying drawings. These directions or approximate terms are only used to assist in explaining and understanding the various embodiments of this invention and are not intended to limit the invention.

[0012] The use of the quantifiers “a” or “an” for the elements and components described throughout this invention is for convenience and to provide the general meaning of the scope of the invention; in this invention, it should be interpreted as including one or at least one, and a single concept also includes multiple cases, unless it clearly means otherwise.

[0013] The terms “combination,” “integration,” “assembly,” or “setting” used throughout this invention mainly refer to the types of connections that allow for separation without damaging the components, or connections that make the components inseparable. Those skilled in the art can choose the appropriate term based on the material of the components to be connected or the assembly requirements.

[0014] The planetary roller screw of the present invention comprises: a main screw having a first external thread extending axially along its outer periphery; a nut having a through hole extending axially, the nut having an internal thread extending axially along the inner wall of the through hole; all or part of the first external thread being located within the through hole of the nut; and a planetary assembly having a plurality of rollers, each roller extending axially, and each roller having a second external thread on its outer periphery; each roller being at least partially located within the through hole of the nut, and each second external thread engaging with both the first external thread and the internal thread; the pitch of the first external thread, the pitch of the internal thread, and the pitch of each second external thread are equal; the pitch of the first external thread... The rotation direction is opposite to the helical direction of the internal thread, and the helical direction of the internal thread is the same as the helical direction of the second external thread; one of the main screw or the nut is used as a driving member, and the main screw, the nut, and the other two members of the planetary set that are not the driving members are used as driven members. According to a configuration rule, when the driving member rotates, the driving member produces relative displacement to each driven member in the axial direction, and there is no relative displacement between the two driven members in the axial direction; the configuration rule is that the ratio of the pitch circle diameter between the driven members is the same as the ratio of the number of helixes, and the number of helixes of the nut is not equal to the number of helixes of the main screw plus the number of helixes of the two rollers.

[0015] Therefore, the planetary roller screw of the present invention, by having the nut / internal thread and the roller / second external thread in the same helical direction, and the main screw / first external thread in opposite helical directions, and in accordance with the configuration rules (the ratio of the pitch circle diameter between the driven members to the ratio of the number of helixes is the same, and the number of helixes of the nut is not equal to the number of helixes of the main screw plus the number of helixes of the two rollers), when a specific driving member rotates, can prevent relative displacement between the two driven members in the axial direction, and enable the driven members to generate stable and smooth axial displacement of the driving member, thereby increasing the corresponding displacement reduction ratio and achieving more precise displacement control. In particular, through the motion relationship between the driving member and the driven member in the planetary roller screw of the present invention, the planetary roller screw of the present invention can replace the hydraulic cylinder and be applied to various machine tools, braking devices, robots, and other situations requiring precise control of linear motion.

[0016] In this configuration, the nut is the driving element, and the ratio of the pitch circle diameter of the main screw to the pitch circle diameter of the roller is the same as the ratio of the number of helixes of the main screw to the number of helixes of the roller. When the driving element rotates, the planetary set produces a relative displacement to the nut in the axial direction, while there is no relative displacement between the main screw and the planetary set in the axial direction. Thus, with this configuration, using the nut as the driving element and the main screw or the planetary set as the output, the desired precise motion control and improved structural strength can be achieved.

[0017] In this configuration, the main screw is the driving element, and the ratio of the pitch circle diameter of the nut to the pitch circle diameter of the roller is the same as the ratio of the number of helixes of the nut to the number of helixes of the roller. When the driving element rotates, the planetary set produces a relative displacement to the main screw in the axial direction, while there is no relative displacement between the nut and the planetary set in the axial direction. Thus, with the main screw acting as the driving element and the nut or planetary set acting as the output, the desired precise motion control and improved structural strength can be achieved.

[0018] The planetary assembly also includes a ring frame portion disposed between the main screw and the nut, and has several receiving portions. The number of receiving portions is at least equal to the number of rollers, with each roller housed in one of the corresponding receiving portions. This ring frame configuration ensures that the rollers of the planetary assembly are stably and evenly distributed around the outer circumference of the main screw, thereby ensuring that each roller receives uniform force during rotation and improving the smoothness of the planetary roller screw's operation.

[0019] The ring frame is an annular body, and the plurality of receiving portions each form a plurality of through holes in the radial direction of the ring frame. In the case where each roller receives a corresponding one of the plurality of receiving portions, there is a circumferential gap between each roller and the corresponding receiving portion. Thus, by having a circumferential gap between each roller and the corresponding receiving portion, the smoothness of rotation between each roller and the main screw and the nut can be improved.

[0020] Each roller has a protrusion at both ends in the axial direction. The planetary set also has a ring frame portion disposed between the main screw and the nut. The ring frame portion has two opposing ring bodies in the axial direction, each ring body having multiple opposing recesses in the axial direction. The protrusions of each roller are partially fitted into the corresponding recesses. In this way, the arrangement of the ring frame portion ensures that the rollers of the planetary set are stably and evenly distributed on the outer circumference of the main screw, thereby ensuring that the rollers are evenly stressed when the planetary set rotates, thus improving the smoothness of the planetary roller screw operation.

[0021] Each roller has a corresponding elastic element on its protrusion, and each elastic element abuts against the ring frame and the roller. In this way, each elastic element will maintain a certain tension in the axial direction of each roller, thus ensuring that the roller does not shift axially during operation.

[0022] In this design, the tooth flank of any one of the first external thread of the main screw, the internal thread of the nut, and the second external thread of each roller is arc-shaped. This reduces the contact area between the second external thread of the roller and the first external thread and the internal thread, respectively, thereby reducing the corresponding friction and effectively reducing noise generation and improving rotational smoothness.

[0023] The first external thread of the main screw has at least one main screw tooth, and the second external thread of each roller in the planetary set has at least one roller tooth. When the first and second external threads engage, the at least one main screw tooth and the at least one roller tooth simultaneously engage. This ensures that when the planetary set rotates, each roller rotates in a purely rolling state, eliminating unexpected friction caused by sliding and thus improving the overall smoothness of the planetary roller screw operation.

[0024] The nut has an internal thread with at least one nut tooth, and each roller of the planetary set has a second external thread with at least one roller tooth. During the engagement and rotation of the internal and external threads, the at least one nut tooth and the at least one roller tooth simultaneously engage and rotate. This ensures that when the planetary set rotates, each roller rotates in a purely rolling state, eliminating unexpected friction caused by sliding and thus improving the smoothness of the overall planetary roller screw operation. Attached Figure Description

[0025] Figure 1 A cross-sectional view of the construction of an existing planetary roller screw; Figure 2 : An exploded perspective view of the first embodiment of the planetary roller screw of the present invention; Figure 3 :like Figure 2 Combined cross-sectional view; Figure 4 :like Figure 3 A magnified view of the local structure of region A shown below; Figure 5 : A schematic diagram of the motion relationship of the planetary roller screw of the present invention with the nut as the driving element; Figure 6 : A schematic diagram of the motion relationship of the planetary roller screw of the present invention with the main screw as the driving member; Figure 7 A schematic diagram showing that the main screw and rollers have intermeshing threaded teeth; Figure 8 A schematic diagram showing that the main screw and rollers have meshing threaded teeth and spur gears; Figure 9 A schematic diagram showing that the nut and roller have intermeshing threaded teeth; Figure 10 A schematic diagram showing that the nut and roller have intermeshing threaded teeth and a spur gear; Figure 11 : A schematic diagram of another preferred configuration of the planetary assembly of the planetary roller screw of the present invention; Figure 12 :like Figure 11 A schematic diagram showing the arrangement of elastic elements on the protrusions of each roller.

[0026] Explanation of reference numerals in the attached figures: (This invention) 1: Main screw 1G: Main screw teeth 11: First external thread 11a: Top of threaded portion 11b: Bottom end of threaded section 11F: Tooth ventral side 12: Connecting part 2: Nut 2a: Nut tip 2b: Bottom end of nut 2G: Nut teeth 20: Through hole 21: Internal thread 21F: Tooth ventral side 3: Planetary Group 31: Roller 31a: Roller tip 31b: Roller bottom end 31G: Roller tooth section 311: Second external thread 311F: Tooth ventral side 312: Protrusion 32: Ring frame section 320: Reception Section 321: Ring body 321C: Recessed portion C: Central axis E: Elastic element G: Gap H: Height L: Length P1, P2, P3: Pitch (Prior art) 9: Planetary roller screw 91: Main screw 911: First external thread 92: Nut 921: Internal thread 93: Roller 931: Second external thread. Detailed Implementation

[0027] To make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments of the present invention are described below in detail with reference to the accompanying drawings; in addition, those symbols that are used in different drawings are considered to be the same and their descriptions will be omitted.

[0028] Please refer to Figure 2 , Figure 3As shown, this is a first embodiment of the planetary roller screw of the present invention, including a main screw 1, a nut 2, and a planetary set 3. The planetary set 3 is located inside the nut 2 and surrounds the main screw 1. With the above configuration, the planetary roller screw can further have a specific mode of motion according to a configuration rule proposed according to the present invention; in particular, based on this configuration rule, the planetary roller screw can have a first configuration or a second configuration, each with different modes of motion; the configuration rule will be described in detail below.

[0029] The outer periphery of the main screw 1 has a first external thread 11 extending axially, and the helical direction of the first external thread 11 can be either right-handed or left-handed. Optionally, the outer periphery of the main screw 1 also has a connecting portion 12; preferably, the first external thread 11 can be provided at one end near the main screw 1, and the connecting portion 12 can be provided at the other end near the main screw 1. In addition, to clearly illustrate the directional configuration in this invention, the main screw 1 can be defined as having a central axis C, and the direction extending from the central axis C is defined as the "axial direction" throughout this invention.

[0030] The nut 2 has an axially extending through hole 20, and an internal thread 21 extending axially on the inner wall surface of the through hole 20; the helical direction of the internal thread 21 can be either right-handed or left-handed; in particular, the helical direction of the internal thread 21 is opposite to the helical direction of the first external thread 11. The main screw 1 is at least partially located in the through hole 20 of the nut 2; in particular, all or part of the first external thread 11 of the main screw 1 is located in the through hole 20 of the nut 2; in other words, in the radial direction, all or part of the first external thread 11 is aligned with the internal thread 21.

[0031] The planetary assembly 3 has several rollers 31, and preferably also has a ring holder portion 32. Each roller 31 extends axially, and the outer periphery of each roller 31 has a second external thread 311, the helical direction of which can be either right-handed or left-handed; in particular, the helical direction of the second external thread 311 is the same as the helical direction of the internal thread 21 of the nut 2, that is, the helical direction of the second external thread 311 is opposite to the helical direction of the first external thread 11 of the main screw 1. Each roller 31 is at least partially located in the through hole 20 of the nut 2, and the second external thread 311 of each roller 31 engages with the first external thread 11 and the internal thread 21, respectively. Preferably, each roller 31 is evenly distributed around the outer periphery of the main screw 1 according to its quantity; for example, when the number of the rollers 31 is N, each roller 31 surrounds the outer periphery of the main screw 1 at an interval angle (360 degrees divided by N); N is a positive integer and greater than 1, and preferably is a number that can be divided by 360 degrees.

[0032] Preferably, the planetary set 3 also has a corresponding ring frame portion 32, which is disposed between the main screw 1 and the nut 2, and has a plurality of receiving portions 320. The number of the plurality of receiving portions 320 is at least equal to the number of the plurality of rollers 31, so that each roller 31 can be accommodated in a corresponding receiving portion 320. Specifically, the number of the plurality of receiving portions 320 is M, and each receiving portion 320 is formed in the ring frame portion 32 at an interval angle (360 degrees divided by M); M is a positive integer, and not less than N, and preferably a number divisible by 360 degrees. In this way, through the arrangement of the ring frame portion 32 and each receiving portion 320, the rollers 31 of the planetary set 3 can be stably and evenly distributed on the outer periphery of the main screw 1.

[0033] In this invention Figure 2 In the illustrated embodiment, the ring frame portion 32 extends axially as an annular body with a central through hole. The plurality of receiving portions 320 each form a corresponding plurality of through holes in the radial direction of the ring frame portion 32, and each through hole has a profile corresponding to that of each roller 31, allowing each roller 31 to be received in one of the corresponding receiving portions 320. In one example, when each roller 31 receives one of the corresponding receiving portions 320, there is a considerable circumferential distance between each roller 31 and its corresponding receiving portion 320 to facilitate rotation between each roller 31 and the main screw 1 / first external thread 11 and the nut 2 / internal thread 21. Thus, through the arrangement of the plurality of receiving portions 320 of the ring frame portion 32, not only can the plurality of rollers 31 be easily installed between the main screw 1 and the nut 2, but each roller 31 can also be stably set in the position between the main screw 1 and the nut 2, and is less likely to be misaligned.

[0034] Optionally, each roller 31 may have a protrusion 312 at both ends in the axial direction extending outward from the corresponding roller 31 in the axial direction (especially along the central axis of the roller 31), and the diameter of the protrusion 312 is not greater than the diameter of the roller 31, preferably smaller than the diameter of the roller 31, so that when each roller 31 is disposed in its corresponding receiving portion 320, and when each roller 31 contacts the ring frame portion 32 in the axial direction, each roller 31 contacts the ring frame portion 32 (corresponding to the edge position of the receiving portion 320) through its protrusion 312, thereby reducing the frictional force of each roller 31 when rotating in the receiving portion 320.

[0035] In particular, such as Figure 4 As shown, the pitch P1 of the first external thread 11, the pitch P2 of the internal thread 21, and the pitch P3 of the second external thread 311 are equal.

[0036] Preferably, the flange 311F of the second external thread 311 is arc-shaped to reduce the contact area between the second external thread 311 of the roller 31 and the first external thread 11 and the internal thread 21, respectively. This reduces the friction between the second external thread 311 and the first external thread 11 and the internal thread 21, thereby reducing noise generation and improving rotational smoothness. It should be noted that in other examples, any one of the flange 11F of the first external thread 11, the flange 21F of the internal thread 21, and the flange 311F of the second external thread 311 may be arc-shaped; this invention is not limited thereto.

[0037] Special attention should be paid to, such as Figures 2-4 As shown, the axial height of each roller 31 positioned between the main screw 1 and the nut 2 varies depending on the lead angle of the main screw 1 and the nut 2, and the circumferential position (with relative angular differences) of each roller 31 on the main screw 1 and the nut 2. In a practical example, each receiving portion 320 on the ring frame portion 32, in order to accommodate the aforementioned variation in the axial height of each roller 31, may have a through-hole height H in the axial direction that is larger than the length L of each roller 31, and thus have the aforementioned gap G (e.g., Figure 5 , Figure 6 As shown), the height H of the through hole is not less than 0.5 pitch P3 longer than the length L of each roller 31, and preferably not less than 1 pitch P3. Optionally, in another example (not shown), to facilitate easy placement of each roller 31 between the main screw 1 and the nut 2, the axial height configuration of each receiving portion 320 on the ring frame portion 32 can vary according to actual needs. Alternatively, in yet another example (not shown), without changing the axial height configuration of each receiving portion 320, the axial height can be adjusted by varying the length of the protrusions 312 at both ends of each roller 31, so that when each roller 31 is placed in the corresponding receiving portion 320, it can have a corresponding axial height suitable for placement on the main screw 1 and / or the nut 2.

[0038] Based on the above Figures 2-4In this invention, a configuration rule is proposed. Based on the condition that the helical direction of the first external thread 11 of the main screw 1 is opposite to the helical direction of the internal thread 21 of the nut 2, and the helical direction of the internal thread 21 of the nut 2 is the same as the helical direction of the second external thread 311 of each roller 31, one of the main screw 1 or the nut 2 is used as a driving member, and the other two members of the planetary set 3 that are not the driving members are used as driven members respectively. The configuration rule is that the ratio of the pitch circle diameter between the driven members is the same as the ratio of the number of helixes, and the number of helixes of the nut 2 is not equal to the number of helixes of the main screw 1 plus the number of helixes of the two rollers 31. Preferably, the number of helixes of the nut 2 is equal to the sum of the number of helixes of the main screw 1 and the two rollers 31, plus or minus 1; or, the number of helixes of the main screw 1 is equal to the minus the number of helixes of the nut 2 and the two rollers 31, plus or minus 1. Thus, according to the above configuration rules, when the driving member is rotated, it generates relative displacement in the axial direction over each driven member, while there is no relative displacement between the two driven members in the axial direction.

[0039] In detail, Figure 5 This shows a first configuration example based on the above configuration rules, with the nut 2 as the driving member. The ratio of the pitch circle diameter of the main screw 1 to the pitch circle diameter of the roller 31 is the same as the ratio of the number of helixes of the main screw 1 to the number of helixes of the roller 31. However, the number of helixes of the nut 2 is not equal to the number of helixes of the main screw 1 plus the number of helixes of the two rollers 31 (or, the number of helixes of the main screw 1 is not equal to the number of helixes of the nut 2 minus the number of helixes of the two rollers 31). This will make the ratio of the pitch circle diameter of the nut 2 to the pitch circle diameter of the roller 31 different from the ratio of the number of helixes of the nut 2 to the number of helixes of the roller 31. To clearly illustrate the configuration rules, let T1 and D1 represent the number of helixes and pitch circle diameter of the main screw 1, respectively; let T2 and D2 represent the number of helixes and pitch circle diameter of the nut 2, respectively; and let T3 and D3 represent the number of helixes and pitch circle diameter of the stud 31, respectively. The first configuration in the configuration rules can be expressed as D1 / D3 = T1 / T3 and T2≠T1+2T3 (T1≠T2-2T3), such that D2 / D3≠T2 / T3. Preferably, the number of helixes of the nut 2 is equal to the number of helixes of the main screw 1 plus the number of helixes of the two rollers 31, plus or minus 1; that is, it can be expressed as T2 = T1+2T3±1. Preferably, the number of helixes of the main screw 1 is equal to the pitch circle diameter of the main screw 1 divided by the pitch circle diameter of the roller 3; that is, it can be expressed as T1 = D1 / D3.

[0040] More specifically, in a specific example of this first configuration, the pitch of the main screw 1, the nut 2, and the roller 31 is all 1.5 mm. The pitch circle diameter of the main screw 1 is 18 mm and the number of helices is 3. The pitch circle diameter of the roller 31 is 6 mm and the number of helices is 1. The pitch circle diameter of the nut 2 is 30 mm and the number of helices is 6. When the nut 2 rotates one revolution, the main screw 1 produces a relative displacement of approximately 0.8 mm relative to the nut 2. In other words, in this case, taking the lead of the nut 2 rotating one revolution as its pitch of 1.5 mm multiplied by the number of helices of 6, which equals 9 mm, and dividing by the displacement of the main screw 1 or planetary gear set 3 as 0.8 mm, we can obtain a corresponding displacement reduction ratio of approximately 11.25 times.

[0041] In detail, Figure 6 This illustrates a second configuration example based on the aforementioned configuration rules. With the main screw 1 as the driving member, the ratio of the pitch circle diameter of the nut 2 to the pitch circle diameter of the roller 31 is the same as the ratio of the number of helixes of the nut 2 to the number of helixes of the roller 31. However, the number of helixes of the nut 2 is not equal to the number of helixes of the main screw 1 plus the number of helixes of the two rollers 31. This ensures that the ratio of the pitch circle diameter of the main screw 1 to the pitch circle diameter of the roller 31 is different from the ratio of the number of helixes of the main screw 1 to the number of helixes of the roller 31. In other words, the second configuration in the configuration rules can be represented as D2 / D3 = T2 / T3 and T2 ≠ T1 + 2T3, such that D1 / D3 ≠ T1 / T3. Preferably, the number of helixes of the main screw 1 is equal to the number of helixes of the nut 2 minus the number of helixes of the two rollers 31, plus or minus 1; that is, it can be expressed as T1 = T2-2T3±1.

[0042] More specifically, in a specific example of this second configuration, the pitch of the main screw 1, the nut 2, and the roller 31 is all 4 mm. The pitch circle diameter of the main screw 1 is 30 mm and the number of helices is 4. The pitch circle diameter of the roller 31 is 10 mm and the number of helices is 1. The pitch circle diameter of the nut 2 is 50 mm and the number of helices is 5. When the main screw 1 rotates one revolution, the nut 2 produces a relative displacement of approximately 2 mm relative to the main screw 1. In other words, in this case, taking the lead of the main screw 1 rotating one revolution as its pitch of 4 mm multiplied by the number of helices of 4, which equals 16 mm, and dividing by the nut 2 or planetary gear 3 as the output displacement of 2 mm, we can obtain a corresponding displacement reduction ratio of approximately 8 times.

[0043] Preferably, in another specific example of this second configuration, an additional condition is satisfied: the number of helixes of the main screw 1 is equal to the pitch circle diameter of the main screw 1 divided by the pitch circle diameter of the roller 3; that is, it can be expressed as T1 = D1 / D3. The pitches of the main screw 1, the nut 2, and the roller 31 are all equal. The pitch circle diameter of the main screw 1 is 20 mm and the number of helixes is 1. The pitch circle diameter of the roller 31 is 20 mm and the number of helixes is 2. The pitch circle diameter of the nut 2 is 60 mm and the number of helixes is 6. In this example, the following formulas are satisfied: D2 / D3 = T2 / T3, T1 = D1 / D3, and T1 = T2-2T3-1 (D1 / D3≠ T1 / T3).

[0044] It should be noted that, based on the mechanism of the planetary roller screw of the present invention, the helical directions of the internal thread 21 and the second external thread 311 are in the same direction, and the helical direction of the first external thread 11 is in the opposite direction; in other words, the component configuration from the outside to the inside can be regarded as [nut 2-roller 31-main screw 1], and the corresponding helical direction can be represented as [right-right-left] or [left-left-right].

[0045] It should be noted that, according to the planetary roller screw of the present invention Figure 5 , Figure 6 In the configuration rule described above, under the reference that the pitch circle diameters of the main screw 1, the nut 2, and the roller 31 are all in the same ratio of 3:5:1, in the first configuration where the nut 2 is the driving member, the displacement reduction ratio is approximately 11.25 times; in the second configuration where the main screw 1 is the driving member, the displacement reduction ratio is approximately 8 times. However, applying similar configuration conditions to the prior art where all helical directions are the same, such that the pitch circle diameter ratio of the main screw 91, the nut 92, and the roller 93 is also 3:5:1, the pitch is 4 mm, the pitch circle diameter of the main screw 91 is 30 mm and the number of helical lines is 5, the pitch circle diameter of the roller 93 is 10 mm and the number of helical lines is 1, and the pitch circle diameter of the nut 92 is 50 mm and the number of helical lines is 5; with the main screw 91 as the driving member and rotating the main screw one revolution, the relative displacement of the nut 92 relative to the main screw 91 is approximately 20 mm. In other words, in this case, the lead of one revolution of the main screw 91 is its pitch of 4 mm multiplied by the number of helixes of 5, which equals 20 mm. Dividing this by the nut 92 as the output displacement of 20 mm, we can obtain a displacement reduction ratio of 1. That is, based on similar configuration conditions, the planetary roller screw proposed in this invention has a better displacement reduction ratio. It should also be noted that the specific proportional relationships of the pitch circle diameters between the various components mentioned in this invention, as well as the specific values ​​of the pitch, pitch circle diameter, and / or number of helixes of each component, are merely examples to more clearly illustrate the content of this invention and are not intended to limit this case.

[0046] Therefore, based on the helical direction configuration and configuration rules proposed in this invention, using the same or similar pitch configuration as the prior art, this invention can reduce the relative displacement between the main screw 1 and the nut 2, thereby achieving more precise motion control. Furthermore, since the pitch configuration conditions corresponding to the main screw 1, the nut 2, and the roller 31 remain unchanged (not adjusted to be more compact), without additional increase in processing costs, the main screw 1, the nut 2, and the roller 31 can maintain the same load-bearing capacity. In other words, compared to the prior art, to achieve the same displacement accuracy control—that is, when the driven component rotates one revolution and the driven component has the same displacement—the pitch of this invention can be larger, resulting in better load-bearing capacity and reduced manufacturing costs.

[0047] Please refer to Figure 7 , Figure 8 As shown, it illustrates another preferred configuration of the main screw 1 and each roller 31 in the planetary roller screw of the present invention. Compared to Figures 2-4 The main screw 1 also has at least one main screw tooth 1G; each roller 31 also has at least one roller tooth 31G, so that when the first external thread 11 and the second external thread 311 generate screwed rotation, the at least one main screw tooth 1G and the at least one roller tooth 31G simultaneously generate meshing rotation; and through the meshing rotation of the at least one main screw tooth 1G and the at least one roller tooth 31G, it can be ensured that when the planetary set 3 rotates (each roller 31 revolves around the main screw 1), each roller 31 rotates in a pure rolling / rotating state, thereby eliminating the situation of unexpected friction caused by sliding, and thus improving the smoothness of the overall planetary roller screw operation.

[0048] exist Figure 7In the example shown, the main screw 1 has a main screw tooth 1G disposed over the entire area of ​​the first external thread 11; however, in other examples (not shown), the main screw tooth 1G may also be disposed in single or multiple segments over a single or multiple local areas of the first external thread 11 or the main screw 1. Each roller 31 has two roller teeth 31G disposed in a local area of ​​the second external thread 311 near its two ends (i.e., the top end 31a and the bottom end 31b) in the axial direction; however, in other examples (not shown), the roller teeth 31G may also be disposed in a single segment over the entire area of ​​the second external thread 311, or may be disposed in single or multiple segments over a single or multiple local areas of the second external thread 311 or the roller 31. In particular, the main screw tooth 1G is a plurality of recessed structures or a plurality of protruding structures formed on the first external thread 11, and the roller tooth 31G is a plurality of recessed structures or a plurality of protruding structures formed on the second external thread 311 of each roller 31 for meshing with the main screw tooth 1G.

[0049] exist Figure 8 In the example shown, it is similar to Figure 7 The main difference lies in the following: the main screw 1 has another main screw tooth section 1G positioned outside one of the two axial ends of the first external thread 11, and this other main screw tooth section 1G has a spur gear structure; one of the two roller tooth sections 31G is positioned outside one of the two axial ends of the second external thread 311, and this roller tooth section 31G has a spur gear structure, meshing with the two main screw tooth sections 1G as a spur gear structure. It should be noted that... Figure 8 The main screw tooth 1G and roller tooth 31G with spur gear structure shown are respectively positioned on the outer sides of the bottom end 11b of the threaded portion and the bottom end 31b of the roller. However, in other configurations, they can also be positioned on the outer sides of the top end 11a of the threaded portion and the top end 31a of the roller. In other examples (not shown), the main screw tooth 1G with a spur gear structure can be configured in two segments, respectively positioned on the outer sides of both ends of the first external thread 11 of the main screw 1, with the first external thread 11 positioned between the two segments of the main screw tooth 1G; the roller tooth 31G with a spur gear structure can be configured in two segments, respectively positioned on the outer sides of both ends of the second external thread 311 of the roller 31, with the second external thread 311 positioned between the two segments of the roller tooth 31G.

[0050] similar Figure 7 , Figure 8 Please refer to Figure 9 , Figure 10This illustrates another preferred configuration of the nut 2 and each roller 31 in the planetary roller screw of the present invention. The nut 2 further has at least one nut tooth 2G; each roller 31 further has at least one roller tooth 31G, such that when the internal thread 21 and the second external thread 311 engage and rotate, the at least one nut tooth 2G and the at least one roller tooth 31G simultaneously engage and rotate; and through the engagement and rotation of the at least one nut tooth 2G and the at least one roller tooth 31G, it can be ensured that when the planetary assembly 3 rotates (each roller 31 revolves around the main screw 1), each roller 31 rotates in a pure rolling / rotating state, thus eliminating the situation of unexpected friction caused by sliding, thereby improving the smoothness of the overall planetary roller screw operation.

[0051] exist Figure 9 In the example shown, the nut 2 has a nut tooth 2G disposed over the entire area of ​​the internal thread 21; however, in other examples (not shown), the nut tooth 2G may also be disposed in single or multiple segments over a single or multiple local areas of the internal thread 21 or the nut 2. Each roller 31 has two roller teeth 31G disposed in a local area of ​​the second external thread 311 near its two ends (i.e., the roller top end 31a and the roller bottom end 31b) in the axial direction; however, in other examples (not shown), the roller teeth 31G may also be disposed in a single segment over the entire area of ​​the second external thread 311, or may be disposed in single or multiple segments over a single or multiple local areas of the second external thread 311 or the roller 31.

[0052] exist Figure 10 In the example shown, it is similar to Figure 9 The main difference lies in the following: the nut 2 has another nut tooth section 2G positioned on the outer side of one of the two axial ends of the internal thread 21, and this other nut tooth section 2G has a spur gear structure; one of the two roller tooth sections 31G is positioned on the outer side of one of the two axial ends of the second external thread 311, and this roller tooth section 31G also has a spur gear structure, meshing with the spur gear structure of the two nut tooth sections 2G. It should be noted that... Figure 10The nut teeth 2G and roller teeth 31G with spur gear structures shown are respectively positioned on the outer sides of the nut bottom end 2b and the roller bottom end 31b. However, in other configurations, they can also be positioned on the outer sides of the nut top end 2a and the roller top end 31a. In other examples (not shown), the nut teeth 2G with a spur gear structure can be arranged in two segments, respectively positioned on the outer sides of both ends of the internal thread 21 of the nut 2, with the internal thread 21 positioned between the two segments of the nut teeth 2G; similarly, the roller teeth 31G with a spur gear structure can be arranged in two segments, respectively positioned on the outer sides of both ends of the second external thread 311 of the roller 31, with the second external thread 311 positioned between the two segments of the roller teeth 31G.

[0053] It should be noted that, according to Figures 7-10 As shown, in order to enable each roller 31 to form a pure rolling motion with respect to the main screw 1 and the nut 2, the "teeth" of the present invention can be disposed on the main screw 1 and each roller 31, or on the nut 2 and each roller 31, or on the main screw 1, the nut 2 and each roller 31; the teeth refer to the main screw teeth 1G, the nut teeth 2G and the roller teeth 31G. In particular, the position and area / range of the teeth disposed on the main screw 1, the nut 2 and each roller 31 can be set according to the range of motion between the main screw 1, the nut 2 and each roller 31. In particular, when forming the corresponding tooth features, the pitch circle diameters corresponding to the first external thread 11, the internal thread 21 and the second external thread 311 need to be considered, and it is preferable that the smallest of these pitch circle diameters is divisible by the others.

[0054] It should also be noted that the present invention Figure 8 , Figure 10 The teeth shown are designed to achieve meshing rotation in parallel axial direction using a spur gear structure. However, the present invention is not limited to spur gears and includes other structures that can achieve meshing rotation in parallel axial direction.

[0055] Additionally, please refer to Figure 11 This illustrates another preferred configuration of the planetary set 3 in the planetary roller screw of the present invention. The ring carrier portion 32 of the planetary set 3 has two opposing rings 321 arranged axially. Each of the two rings 321 has a plurality of opposing recesses 321C in the axial direction, for the protrusions 312 of each roller 31 to be partially fitted into the corresponding recesses 321C; in particular, each roller 31 may be presented as... Figure 2 , Figures 7-10 The structure. It should be noted that this invention... Figure 12Although the recessed portion 321C is a perforation, the construction of the recessed portion 321C is not limited to this; for example, the recessed portion 321C can form a recessed and non-perforated structure.

[0056] Optionally, such as Figure 12 As shown, a corresponding elastic element E is provided on the protrusion 312 of the roller 31, and each elastic element E abuts between the ring frame portion 32 and the roller 31; thus, each elastic element E will maintain a certain tension in the axial direction of each roller 31, thereby ensuring that each roller 31 does not shift axially during operation. Preferably, the elastic element E can be constructed as a coil spring.

[0057] According to the configuration and motion mechanism of the planetary roller screw of the present invention, one of the main screw 1, the nut 2, and the planetary set 3 can be the driving member, and the other two of the main screw 1, the nut 2, and the planetary set 3 can be the driven members. When the driving member rotates, the direction of linear movement of the planetary set 3 relative to the nut 2 is opposite to the direction of linear movement of the main screw 1 relative to the planetary set 3. In addition, in order to achieve the required motion relationship and accuracy between the main screw 1, the nut 2, and the roller 31, this can be achieved by adjusting the pitch circle diameter, number of helixes, and pitch of the main screw 1, the nut 2, and the roller 31, respectively.

[0058] In summary, the planetary roller screw of the present invention, by having the nut / internal thread and the roller / second external thread in the same helical direction, and the main screw / first external thread in opposite helical directions, and in accordance with the configuration rules (the ratio of the pitch circle diameter between the driven members to the ratio of the number of helixes is the same, and the number of helixes of the nut is not equal to the number of helixes of the main screw plus the number of helixes of the two rollers), ensures that no relative displacement occurs between the two driven members in the axial direction when a specific driving member rotates, and enables the driven members to generate stable and smooth axial displacement relative to the driving member, thereby increasing the corresponding displacement reduction ratio and achieving more precise displacement control. In particular, through the kinematic relationship between the driving and driven members in the planetary roller screw of the present invention, the planetary roller screw of the present invention can replace the hydraulic cylinder and be applied to various machine tools, braking devices, robots, and other situations requiring precise control of linear motion.

[0059] It should be noted that, according to the above-mentioned configuration rules, especially based on the specific relationship between the pitch circle diameter and the number of helixes between the main screw, the nut and the roller, the planetary roller screw of the present invention can still achieve smooth operation without the need for the configuration of the main screw teeth, the nut teeth and the roller teeth, that is, without the need for any of the main screw teeth, the nut teeth and the roller teeth.

[0060] Although the present invention has been disclosed using the above preferred embodiments, it is not intended to limit the invention. Any modifications and alterations made by those skilled in the art to the above embodiments without departing from the spirit and scope of the invention still fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention includes all changes within the meaning and equivalent scope of the appended claims. Furthermore, when the above embodiments can be combined, the present invention includes any combination of embodiments.

Claims

1. A planetary roller screw, characterized in that, include: A main screw, the outer circumference of which has a first external thread extending along an axial direction; A nut having an axially extending through hole, the nut having an internal thread extending axially on the inner wall surface of the through hole; all or part of the first external thread of the main screw is located within the through hole of the nut; and A planetary assembly has a plurality of rollers, each roller extending axially and having a second external thread on its outer periphery; each roller is at least partially located in the through hole of the nut, and the second external thread of each roller is respectively screwed into the first external thread and the internal thread; The pitches of the first external thread, the internal thread, and the second external thread are equal; the helical direction of the first external thread is opposite to that of the internal thread, and the helical direction of the internal thread is the same as that of the second external thread; one of the main screw or the nut is designated as a driving member, and the main screw, the nut, and the other two members of the planetary set that are not driving members are defined as driven members respectively. According to a configuration rule, when the driving member rotates, the driving member generates relative displacement in the axial direction to each driven member, and no relative displacement occurs between the two driven members in the axial direction; the configuration rule is that the ratio of the pitch circle diameter between the driven members is the same as the ratio of the number of helixes, and the number of helixes of the nut is not equal to the number of helixes of the main screw plus the number of helixes of the two rollers.

2. The planetary roller screw as described in claim 1, characterized in that, In this configuration rule, the nut is the driving member, and the ratio of the pitch circle diameter of the main screw to the pitch circle diameter of the roller is the same as the ratio of the number of helixes of the main screw to the number of helixes of the roller. When the driving member is rotated, the planetary set produces a relative displacement to the nut in the axial direction, and there is no relative displacement between the main screw and the planetary set in the axial direction.

3. The planetary roller screw as described in claim 1, characterized in that, In this configuration rule, the ratio of the pitch circle diameter of the nut to the pitch circle diameter of the roller is the same as the ratio of the number of helixes of the nut to the number of helixes of the roller; when the driving member is rotated, the planetary set produces a relative displacement to the main screw in the axial direction, and there is no relative displacement between the nut and the planetary set in the axial direction.

4. The planetary roller screw as described in any one of claims 1 to 3, characterized in that, The planetary assembly also has a ring frame portion disposed between the main screw and the nut. The ring frame portion has several receiving portions, the number of which is at least equal to the number of rollers, and each roller is received in one of the corresponding receiving portions.

5. The planetary roller screw as described in claim 4, characterized in that, The ring frame is an annular body, and the plurality of receiving parts each form a plurality of through holes in the radial direction of the ring frame; in the case where each roller receives one of the plurality of receiving parts, there is a circumferential gap between each roller and the corresponding receiving part.

6. The planetary roller screw as described in any one of claims 1 to 3, characterized in that, Each roller has a protrusion at both ends in the axial direction; the planetary assembly also has a ring frame portion disposed between the main screw and the nut, the ring frame portion having two ring bodies arranged opposite each other in the axial direction, the two ring bodies each having a plurality of recesses opposite each other in the axial direction; the protrusion of each roller is partially fitted into the corresponding recess.

7. The planetary roller screw as described in claim 6, characterized in that, Each protrusion of each roller is provided with a corresponding elastic element, and each elastic element abuts between the ring frame and the roller.

8. The planetary roller screw as described in any one of claims 1 to 3, characterized in that, The tooth belly of any one of the first external thread of the main screw, the internal thread of the nut, and the second external thread of each roller is arc-shaped.

9. The planetary roller screw as described in any one of claims 1 to 3, characterized in that, The first external thread of the main screw has at least one main screw tooth, and the second external thread of each roller of the planetary assembly has at least one roller tooth; in the case of engagement rotation between the first external thread and the second external thread, engagement rotation occurs between the at least one main screw tooth and the at least one roller tooth.

10. The planetary roller screw as described in any one of claims 1 to 3, characterized in that, The internal thread of the nut has at least one nut tooth, and the second external thread of each roller of the planetary assembly has at least one roller tooth; in the case where engagement rotation occurs between the internal thread and the second external thread, engagement rotation occurs between the at least one nut tooth and the at least one roller tooth.

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