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 during precise motion control. The main screw rod is provided with an external thread; the nut is provided with an internal thread; the planet group is provided with a plurality of rollers, and the periphery of each roller is provided with a roller external thread; the thread pitch of the external thread, the thread pitch of the internal thread and the thread pitch of the roller external thread are equal; the spiral direction of the external thread of the main screw is opposite to the spiral direction of the internal thread of the nut; the main screw or the nut is used as a driving part, and when the driving part is rotated, the direction of linear movement of the planet set to the nut is opposite to the direction of linear movement of the main screw to the planet set. According to the invention, the effect of precise motion control can be achieved.

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 relates to a planetary roller screw 9, which comprises a main screw 91 and a nut 92 with a plurality of rollers 93 disposed between them. The main screw 91 has an external thread 911, and the nut 92 has an internal thread 921 and non-threaded portions 922 on both sides of the internal thread 921. The non-threaded portions 922 accommodate a collar 94, which has internal ring teeth 941 and a fixing plate 95. The plurality of rollers 93 are identical to each other and have rollers. The main screw 91 has an external thread 931 and an external toothed portion 932. The two ends of the plurality of rollers 93 are respectively fitted onto the two fixing plates 95. The plurality of rollers 93 are distributed at equal angular intervals around the main screw 91 and are coaxial with the main screw 91. The external threads 931 of the rollers 93 mesh with the internal threads 921 of the nut 92 and the external threads 911 of the main screw 91. The external teeth 932 of the rollers 93 mesh with the inner ring teeth 941 of the collar 94. Thus, with the above configuration, when the main screw 91 or the nut 92 is rotated, the nut 92 and the plurality of rollers 93 will synchronously produce the same relative displacement to the main screw 91 in the axial direction.

[0004] Based on the existing motion mechanism of the planetary roller screw 9, one of the main screw 91 or the nut 92 to be rotated is defined as the driving member, and the other of the main screw 91 or the nut 92 that produces linear movement is defined as the driven member. When the main screw 91, the nut 92, and the rollers 93 have a large pitch, the linear movement of the driven member caused by one rotation of the driving member 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 member caused by one rotation of the driving member is small, resulting in a low linear movement speed, but the movement can be precisely controlled, although the load-bearing capacity of each component is reduced.

[0005] Therefore, in applications such as electric vehicles and humanoid robots, the existing planetary roller screw 9 cannot simultaneously achieve the effects of precise control of movement and large load-bearing capacity.

[0006] In view of this, there is indeed a need to improve the existing planetary roller screw. Summary of the Invention

[0007] 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.

[0008] 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.

[0009] 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.

[0010] 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.

[0011] The planetary roller screw of the present invention comprises: a main screw having an 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 external thread of the main screw 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 an external roller thread on its outer periphery; each roller being at least partially located within the through hole of the nut, and the external roller thread of each roller engaging with both the external thread and the internal thread; the pitch of the external thread of the main screw, the pitch of the internal thread of the nut, and the pitch of the external roller thread of each roller are equal. The helical direction of the external thread of the main screw is opposite to the helical direction of the internal thread of the nut; with the main screw or the nut as a driving member, when the driving member is rotated, the direction of the linear movement of the planetary set relative to the nut is opposite to the direction of the linear movement of the main screw relative to the planetary set, causing a non-zero deceleration displacement between the main screw and the nut; the number of helical lines of the external thread of the main screw is not equal to the number of helical lines of the roller external thread multiplied by the pitch circle diameter of the external thread of the main screw divided by the pitch circle diameter of the roller external thread, and / or the number of helical lines of the internal thread is not equal to the number of helical lines of the external thread of the main screw plus the number of helical lines of two roller external threads.

[0012] Therefore, the planetary roller screw of the present invention, through the configuration and connection relationship of the main screw, the nut and the plurality of rollers, will generate a corresponding deceleration displacement when the driving member is rotated, so as to achieve the effect of precise control of the amount of movement.

[0013] The nut has multiple helixes on its internal thread, and the main screw has multiple helixes on its external thread. Thus, based on the fact that the planetary roller screw uses either the nut or the main screw as the driving element, and considering the relatively small pitch circle diameter of each roller's external thread, by using multiple helixes on the internal and external threads, and by correspondingly adjusting the relationship between the pitch circle diameter, helix count, and pitch of each of the external, internal, and roller external threads, the desired deceleration displacement can be obtained, achieving precise control of the movement.

[0014] In this embodiment, the number of helixes on the internal thread of the nut differs from the number of helixes on the external thread of the main screw. Thus, based on the implementation of the integral planetary roller screw with either the nut or the main screw as the driving element, a desired deceleration displacement can be obtained by adjusting the pitch circle diameter, number of helixes, and pitch of the external thread, internal thread, and roller external thread according to the difference in the number of helixes. In particular, it is easier to design a smaller deceleration displacement to achieve precise control of the movement.

[0015] The internal thread of the nut has the same helical direction as the external thread of each roller. Thus, the appropriate helical direction (left-hand or right-hand) can be selected based on application requirements to determine the effectiveness of the corresponding motion characteristics.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] In this design, the tooth flank of any one of the following: the external thread of the main screw, the internal thread of the nut, and the external thread of each roller. This reduces the contact area between the external thread of the roller and the external and internal threads, thereby reducing the corresponding friction and effectively reducing noise generation and improving rotational smoothness.

[0021] The main screw has at least one main screw tooth on its external thread, and each roller in the planetary assembly has at least one roller tooth on its external thread. During engagement rotation between the external thread and the roller thread, the at least one main screw tooth and the at least one roller tooth simultaneously engage rotation. This ensures that when the planetary assembly 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.

[0022] The nut has an internal thread with at least one nut tooth, and each roller in the planetary set has an external thread with at least one roller tooth. During the engagement and rotation between 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 overall smoothness of the planetary roller screw operation. Attached Figure Description

[0023] Figure 1 A cross-sectional view of the construction of an existing planetary roller screw; Figure 2 An exploded perspective view of a 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.

[0024] Explanation of reference numerals in the attached figures: [This invention] 1: Main screw 11: External thread 11a: Top of threaded portion 11b: Bottom end of threaded section 11F: Tooth ventral side 1G: Main screw teeth 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 31G: Roller tooth section 31a: Roller tip 31b: Roller bottom end 311: Roller external thread 311F: Tooth ventral side 312: Protrusion 32: Ring frame section 320: Reception Section 321: Ring body 321C: Recessed portion C: Central axis d1: First distance d2: Second distance E: Elastic element G: Gap H: Height L: Length ﹝existing﹞ 9: Planetary roller screw 91: Main Screw 911: External thread 92: Nut 921: Internal thread 922: Non-threaded 93: Roller 931: Roller External Thread 932: External teeth 94: Collar 941: Inner ring teeth 95: Fixing plate. Detailed Implementation

[0025] 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.

[0026] Please refer to Figure 2 , Figure 3 As 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, when the nut 2 rotates about its axial direction, the planetary set 3 can move linearly about its axial direction relative to the nut 2 and the main screw 1, and the direction of the linear movement of the planetary set 3 relative to the nut 2 is opposite to the direction of the linear movement of the main screw 1 relative to the planetary set 3; or, when the main screw 1 rotates about its axial direction, the planetary set 3 can move linearly about its axial direction relative to the main screw 1 and the nut 2, and the direction of the linear movement of the planetary set 3 relative to the main screw 1 is opposite to the direction of the linear movement of the nut 2 relative to the planetary set 3; that is, similarly, the direction of the linear movement of the planetary set 3 relative to the nut 2 is opposite to the direction of the linear movement of the main screw 1 relative to the planetary set 3.

[0027] The outer periphery of the main screw 1 has an external thread 11 extending axially, and the helical direction of the 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 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" as described throughout this invention.

[0028] 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 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 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 external thread 11 is aligned with the internal thread 21.

[0029] 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 circumference of each roller 31 has a roller external thread 311, the helical direction of which can be either right-handed or left-handed; in particular, the helical direction of the roller 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 roller external thread 311 is opposite to the helical direction of the 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 roller external thread 311 of each roller 31 engages with the 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.

[0030] 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.

[0031] 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 gap between each roller 31 and the corresponding receiving portion 320 to facilitate rotation between each roller 31 and the main screw 1 / 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.

[0032] 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.

[0033] Through the configuration / connection relationship between the main screw 1, the nut 2, and the planetary set 3 described above, when the nut 2 rotates axially, the planetary set 3 / each roller 31 can move linearly axially relative to the nut 2 and the main screw 1. Alternatively, when the main screw 1 rotates axially, the nut 2 and the planetary set 3 / each roller 31 can move linearly axially relative to the main screw 1 and the nut 2. Similarly, when the planetary set 3 rotates axially, the main screw 1 and the nut 2 can also move linearly axially relative to the planetary set 3, and the main screw 1 produces a relative linear movement to the nut 2. In other words, under the configuration of the planetary roller screw of the present invention, when the main screw 1 or the nut 2 rotates axially as the driving member, the direction of the linear movement of the planetary set 3 to the nut 2 is opposite to the direction of the linear movement of the main screw 1 to the planetary set 3, thereby generating a deceleration displacement to achieve precise motion control.

[0034] To elaborate, such as Figure 4 As shown, in order to achieve the above-mentioned mechanism of deceleration displacement, the pitch P1 of the external thread 11, the pitch P2 of the internal thread 21, and the pitch P3 of the roller external thread 311 are equal.

[0035] Preferably, the flange 311F of the external roller thread 311 is arc-shaped to reduce the contact area between the external roller thread 311 and the external thread 11 and the internal thread 21, respectively. This reduces the friction between the external roller thread 311 and the 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 external thread 11, the flange 21F of the internal thread 21, and the flange 311F of the external roller thread 311 may be arc-shaped; this invention is not limited thereto.

[0036] 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 6As 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.

[0037] To elaborate, such as Figure 5 As shown, to more clearly illustrate the operating mechanism of the planetary roller screw of the present invention, and particularly to explain the relationship between the rotation direction and the linear movement direction among the components, the external thread 11 of the main screw 1 is further defined to have an axially opposite threaded tip 11a and a threaded bottom end 11b, the nut 2 has an axially opposite nut tip 2a and nut bottom end 2b, and each roller 31 has an axially opposite roller tip 31a and roller bottom end 31b. The threaded tip 11a, the nut tip 2a, and the roller tip 31a define a first direction; the threaded bottom end 11b, the nut bottom end 2b, and the roller bottom end 31b define a second direction.

[0038] exist Figure 5 In the example shown, the helical direction of the internal thread 21 of the nut 2 and the helical direction of the external thread 311 of the roller 31 are both right-handed, while the helical direction of the external thread 11 of the main screw 1 is left-handed. Taking the nut 2 as the driving member rotating clockwise (i.e., in the same direction as the helical direction of the nut 2) around the central axis C of the main screw 1, the internal thread 21 will drive each roller 31 to revolve around the central axis C of the main screw 1 in the same direction (clockwise) as the nut 2. At this time, the rollers 31 / the planetary set 3 as a whole will produce relative linear movement with the nut 2 in the axial direction, and the rollers 31 will move linearly in the second direction (i.e., towards the bottom end 2b of the nut).

[0039] Next, through the connection relationship where the helical direction of the external thread 311 of each roller 31 is opposite to the helical direction of the external thread 11 of the main screw 1, the plurality of rollers 31 as a whole generate relative linear movement with respect to the main screw 1 in the axial direction, and the main screw 1 generates relative linear movement in the direction of the first direction / the thread tip 11a. It should be particularly noted that, with the above configuration, the main screw 1 can generate only linear movement in the axial direction without generating rotational movement in the circumferential direction, and the direction of linear movement of the planetary set 3 towards the nut 2 is opposite to the direction of linear movement of the main screw 1 towards the planetary set 3.

[0040] based on Figure 5 The configuration and motion relationship are shown, and a first distance d1 is defined between the top end 11a of the threaded portion and the top end 31a of the roller, and a second distance d2 is defined between the top end 31a of the roller and the bottom end 2b of the nut. When the main screw 1 moves in the first direction, the first distance d1 becomes longer, and at the same time, each roller 31 moves in the second direction, the second distance d2 becomes shorter. Since the main screw 1 is set on the planetary set 3 formed by each roller 31, a decelerated displacement will be generated between the main screw 1 and the nut 2 in the axial direction. The decelerated displacement can be defined by the difference in distance between the top end 11a of the threaded portion and the top end 2a of the nut before and after the movement. That is, the decelerated displacement can be calculated by the sum of the change in the first distance d1 and the change in the second distance d2.

[0041] Similarly, based on Figure 5 As shown in the configuration and motion relationship, when the nut 2 rotates counterclockwise, the main screw 1 will move linearly in the second direction, thus shortening the first distance d1. The several rollers 31 will move linearly in the first direction, thus lengthening the second distance d2. Similarly, the deceleration displacement will be generated in the axial direction between the main screw 1 and the nut 2.

[0042] In another example, such as Figure 6 As shown, its continuation Figure 5 The configuration is different, but taking the main screw 1 as the driving member and rotating counterclockwise around the central axis C of the main screw 1 as an example, the external thread 11 will drive each roller 31 to revolve around the central axis C of the main screw 1 in the same direction (counterclockwise) as the main screw 1; at this time, the rollers 31 as a whole will move relatively linearly with the main screw 1 in the axial direction, and the rollers 31 will move linearly in the second direction (i.e., towards the bottom end 2b of the nut).

[0043] Next, the helical direction of the external threads 311 of each roller 31 is in the same direction as the helical direction of the internal threads 21 of the nut 2. The rollers 31 / the planetary set 3 as a whole move linearly relative to the nut 2 in the axial direction, and the nut 2 moves linearly relative to the first direction (i.e., towards the tip 11a of the thread). It should be particularly noted that, with the above configuration, the nut 2 can only produce linear movement in the axial direction, without rotational movement in the circumferential direction, and the direction of linear movement of the planetary set 3 relative to the main screw 1 is opposite to the direction of linear movement of the nut 2 relative to the planetary set 3.

[0044] based on Figure 6 As shown in the configuration and motion relationship, the nut 2 can be regarded as being set on the planetary set 3 formed by each roller 31. When the rollers 31 move in the second direction, the first distance d1 becomes longer, and at the same time, the nut 2 moves in the first direction, the second distance d2 becomes shorter. Since the nut 2 is set on the planetary set 3 formed by each roller 31, the main screw 1 and the nut 2 will eventually produce the aforementioned deceleration displacement in the axial direction.

[0045] based on Figure 6 As shown in the configuration and motion relationship, when the main screw 1 rotates clockwise, the plurality of rollers 31 will move linearly in the first direction, thereby shortening the first distance d1, and the nut 2 will move linearly in the second direction, thereby lengthening the second distance d2. Similarly, the deceleration displacement will be generated in the axial direction between the main screw 1 and the nut 2.

[0046] 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 external roller thread 311 are in the same direction, while the helical direction of the external thread 11 is opposite. Therefore, although the configuration of the internal thread 21 and the external roller thread 311 of the planetary roller screw of the present invention is right-handed and the helical direction of the external thread 11 is left-handed, i.e., the configuration of the components 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], the present invention naturally includes a configuration in which the helical direction of the internal thread 21 and the external roller thread 311 is left-handed and the helical direction of the external thread 11 is right-handed; the corresponding helical direction can be represented as [left-left-right], and the rotation direction and linear movement direction of each component in the aforementioned [left-left-right] configuration and the aforementioned [right-right-left] configuration are opposite.

[0047] It should be particularly noted that, according to the planetary roller screw of the present invention Figures 2-4 Configuration, and Figure 5 , Figure 6The motion mechanism of the planetary roller screw of the present invention, regardless of whether the main screw 1 or the nut 2 is the driving member and rotates around the axial direction, will generate the deceleration displacement. Under the same or similar pitch configuration as the prior art, the relative displacement between the main screw 1 and the nut 2 can be reduced, thereby achieving more precise motion control. Furthermore, since the pitch configuration of the main screw 1, the nut 2, and the roller 31 remains unchanged (not adjusted to a tighter pitch), without additional increasing the corresponding processing costs, the main screw 1, the nut 2, and the roller 31 can maintain the same load-bearing capacity. In other words, compared with... Figure 1 Compared with existing technologies, to achieve the same displacement accuracy control, i.e., when the driven component rotates one revolution, the driven component has the same displacement, the pitch of the present invention can be larger, thus having better load-bearing capacity and saving manufacturing costs.

[0048] It should also be noted that the values ​​of the first distance d1, the second distance d2, and the deceleration displacement are dependent on the pitch circle diameter, number of thread starts, and pitch of each of the external thread 11, the internal thread 21, and the roller external thread 311. Preferably, the pitch circle diameter, number of thread starts, and pitch are designed according to the motion principle of thread engagement understood by those skilled in the art, in order to meet the requirements of the motion relationship and accuracy between the main screw 1, the nut 2, and the roller 31. In particular, the product of the number of thread starts and the pitch is the lead; that is, the configuration of the motion conditions can be considered as related to the pitch circle diameter and the lead.

[0049] Preferably, the internal thread 21 of the nut 2 has multiple helixes, and the external thread 11 of the main screw 1 has multiple helixes. Optionally, the number of helixes of the internal thread 21 of the nut 2 and the number of helixes of the external thread 11 of the main screw 1 can be the same or different. Thus, based on the general implementation of an integral planetary roller screw with either the nut 2 or the main screw 1 as the driving member, and considering the small pitch circle diameter of the external threads 311 of each roller 31, by having multiple helixes for the internal thread 21 and the external thread 11, and by correspondingly adjusting the relationship between the pitch circle diameter, number of helixes, and pitch of each of the external threads 11, the internal thread 21, and the external threads 311, the desired deceleration displacement can be obtained, achieving the effect of precise motion control.

[0050] In particular, in a practical case, the number of helical lines of the internal thread 21 of the nut 2 can be 5, the number of helical lines of the external thread 11 of the main screw 1 can be 4, and the number of helical lines of the external roller thread 311 can be 1. Thus, based on the fact that the integral planetary roller screw is usually implemented with the nut 2 or the main screw 1 as the driving member, and based on the small pitch circle diameter of the external thread 311 of each roller 31, and based on the fact that the pitch circle diameter of the internal thread 21 of the nut 2 is larger than the pitch circle diameter of the external thread 11 of the main screw 1, by making the number of helixes of the internal thread 21 different from that of the external thread 11, especially the number of helixes of the internal thread 21 being greater than that of the external thread 11, and making the number of helixes of the external roller thread one, and by correspondingly adjusting the relationship between the pitch circle diameter, number of helixes, and pitch of the external thread 11, the internal thread 21, and the external roller thread 311, it is easier to design a smaller deceleration displacement to achieve the effect of precise motion control.

[0051] It should be noted that the number of helical lines of the internal thread 21, the external thread 11, and the roller external thread 311 is not limited to those described above. Furthermore, it should be noted that the roller external thread 311 may have multiple helical lines. Additionally, it should be noted that the number of helical lines of the internal thread 21 and / or the external thread 11 may be only one.

[0052] Specifically, in a particular example, when the pitch circle diameter, number of helixes, pitch, and helix direction of the external thread 11, the internal thread 21, and the roller external thread 311 are configured in a specific way, and the pitch circle diameter of the external thread 11 is an integer multiple of the pitch circle diameter of the roller external thread 311, when the nut 2 is rotated as the driving member, no relative displacement occurs between each roller 31 and the main screw 1; under this specific configuration, when the pitch circle diameter of the external thread 11 is not an integer multiple of the pitch circle diameter of the roller external thread 311, when the nut 2 is rotated as the driving member, a relative displacement occurs between each roller 31 and the main screw 1.

[0053] 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 2-4The 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 external thread 11 and the external thread 311 of the roller are engaged in screwed rotation, the at least one main screw tooth 1G and the at least one roller tooth 31G are simultaneously engaged in 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.

[0054] exist Figure 7 In the example shown, the main screw 1 has a main screw tooth 1G disposed over the entire area of ​​the 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 external thread 11 or the main screw 1. Each roller 31 has two roller teeth 31G disposed in a local area of ​​the external thread 311 of the roller 31 axially near both ends (i.e., the top end 31a and the bottom end 31b of the roller); however, in other examples (not shown), the roller teeth 31G may also be disposed in a single segment over the entire area of ​​the external thread 311, or may be disposed in single or multiple segments over a single or multiple local areas of the 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 external thread 11, and the roller tooth 31G is a plurality of recessed structures or a plurality of protruding structures formed on the external thread 311 of each roller 31 for meshing with the main screw tooth 1G.

[0055] 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 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 roller 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 8The 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 may 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 may be configured in two segments, respectively positioned on the outer sides of both ends of the external thread 11 of the main screw 1, with the external thread 11 positioned between the two segments of the main screw tooth 1G; the roller tooth 31G with a spur gear structure may be configured in two segments, respectively positioned on the outer sides of both ends of the external thread 311 of the roller 31, with the external thread 311 positioned between the two segments of the roller tooth 31G.

[0056] similar Figure 7 , Figure 8 Please refer to Figure 9 , Figure 10 This 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 external thread 311 of the roller 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.

[0057] 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 external thread 311 of the roller 31 axially near both ends (i.e., the roller top end 31a and the roller bottom end 31b); however, in other examples (not shown), the roller tooth 31G may also be disposed in a single segment over the entire area of ​​the external thread 311, or may be disposed in single or multiple segments over a single or multiple local areas of the external thread 311 or the roller 31.

[0058] exist Figure 10 In the example shown, it is similar to Figure 9The main difference lies in the following: the nut 2 has another nut tooth portion 2G positioned outside one of the two axial ends of the internal thread 21, and this other nut tooth portion 2G has a spur gear structure; one of the two roller tooth portions 31G is positioned outside one of the two axial ends of the roller external thread 311, and this roller tooth portion 31G has a spur gear structure, meshing with the two nut tooth portions 2G as a spur gear structure. It should be noted that... Figure 10 The 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 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 external thread 311 of the roller 31, with the external thread 311 positioned between the two segments of roller teeth 31G.

[0059] 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 external thread 11, the internal thread 21 and the roller external thread 311 need to be considered, and it is preferable that the smallest of these pitch circle diameters is divisible by the others.

[0060] 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.

[0061] Additionally, please refer to Figure 11This 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 12 Although 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.

[0062] 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.

[0063] According to the configuration and motion mechanism of the planetary roller screw of the present invention, the main screw 1 or the nut 2 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 each of the main screw 1, the nut 2, and the roller 31.

[0064] In summary, the planetary roller screw of the present invention, by having the internal thread of the nut and the external thread of the roller in the same helical direction, and the external thread of the main screw in the opposite helical direction, can generate a deceleration displacement between the main screw and the nut, achieving more precise displacement control. In particular, through the kinematic relationship between the driving and driven components 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.

[0065] 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 an 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 external thread of the main screw is located within the through hole of the nut; and A planetary assembly having a plurality of rollers, each roller extending axially and having an external thread on its outer periphery; each roller is at least partially located in the through hole of the nut, and the external thread of each roller engages with both the external thread and the internal thread. The pitch of the external thread of the main screw, the pitch of the internal thread of the nut, and the pitch of the external thread of each roller are equal; the helical direction of the external thread of the main screw is opposite to the helical direction of the internal thread of the nut. With the main screw or the nut as a driving member, when the driving member is rotated, the direction of the linear movement of the planetary set relative to the nut is opposite to the direction of the linear movement of the main screw relative to the planetary set, so that a non-zero deceleration displacement is generated between the main screw and the nut. The number of helixes on the external thread of the main screw is not equal to the number of helixes on the roller external thread multiplied by the pitch circle diameter of the external thread of the main screw divided by the pitch circle diameter of the roller external thread, and / or the number of helixes on the internal thread is not equal to the number of helixes on the external thread of the main screw plus the number of helixes on two roller external threads.

2. The planetary roller screw as described in claim 1, characterized in that, The nut has multiple helixes in its internal thread, and the main screw has multiple helixes in its external thread.

3. The planetary roller screw as described in claim 2, characterized in that, The number of helixes on the internal thread of the nut is different from the number of helixes on the external thread of the main screw.

4. The planetary roller screw as described in claim 1, characterized in that, The helical direction of the internal thread of the nut is the same as the helical direction of the external thread of each roller.

5. The planetary roller screw as described in any one of claims 1 to 4, 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.

6. The planetary roller screw as described in claim 5, 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 a corresponding one of the plurality of receiving parts, there is a circumferential gap between each roller and the corresponding receiving part.

7. The planetary roller screw as described in any one of claims 1 to 4, 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.

8. The planetary roller screw as described in claim 7, 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.

9. The planetary roller screw as described in any one of claims 1 to 4, characterized in that, The tooth belly of any one of the external thread of the main screw, the internal thread of the nut, and the external thread of each roller is arc-shaped.

10. The planetary roller screw as described in any one of claims 1 to 4, characterized in that, The external thread of the main screw has at least one main screw tooth, and the external thread of each roller of the planetary assembly has at least one roller tooth; in the case of engagement rotation between the external thread and the external roller thread, engagement rotation occurs between the at least one main screw tooth and the at least one roller tooth.

11. The planetary roller screw as described in any one of claims 1 to 4, characterized in that, The internal thread of the nut has at least one nut tooth, and the 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 external thread, engagement rotation occurs between the at least one nut tooth and the at least one roller tooth.

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