Planetary roller screw

Abstract

Conventional planetary roller screws have the problem of insufficient structural strength when controlled by precise movement, and this solves that problem. [Solution] The invention includes a main screw, a nut, and a planetary unit, wherein the main screw has a male thread extending along the axial direction on its outer circumference, the planetary unit has a plurality of rollers, each roller having a roller male thread on its outer circumference, the screw pitch of the male thread of the main screw, the screw pitch of the female thread of the nut, and the screw pitch of the roller male thread of each roller are the same, the helical direction of the male thread of the main screw and the helical direction of the female thread of the nut are opposite, one of the main screw, nut, and planetary unit is the driving part, and when the driving part rotates, the direction of the linear motion of the planetary unit relative to the nut and the direction of the linear motion of the main screw relative to the planetary unit are opposite. The present invention makes it possible to achieve the effect of control by precise movement.

Description

Technical Field

[0001] The present invention relates to the technology of linear translation, and particularly relates to a planetary roller screw.

Background Art

[0002] With the development of industrial technology, especially in the development of electric vehicles and humanoid robots, the planetary roller screw is used to control linear translation. It has characteristics such as being able to withstand high loads, having high positioning accuracy, and high moving speed, so it can replace the conventional hydraulic mechanism.

[0003] As shown in FIG. 12, the conventional planetary roller screw 9 has a plurality of rollers 93 provided between the main screw 91 and the nut 92. The main screw 91 has a male thread 911, and the nut 92 has a female thread 921 and threadless portions 922 on both sides of the female thread 921. The threadless portions 922 accommodate a shaft ring 94, and the shaft ring 94 has an inner annular thread 941 and a fixing plate 95 inside. The plurality of rollers 93 are similar to each other and have a roller male thread 931 and an outer thread portion 932. Also, both ends of the plurality of rollers 93 are respectively pierced through two fixing plates 95. Further, the plurality of rollers 93 are distributed around the main screw 91 at equal angular intervals and are coaxial with the main screw 91. The roller male thread 931 of the plurality of rollers 93 meshes with the female thread 921 of the nut 92 and the male thread 911 of the main screw 91, and the outer thread portion 932 of the plurality of rollers 93 meshes with the inner annular thread 941 of the shaft ring 94. Thus, when the main screw 91 or the nut 92 is rotated by the above-described arrangement, the nut 92 and the plurality of rollers 93 generate the same relative movement amount with respect to the main screw 91 synchronously in the axial direction.

[0004] Based on the motion mechanism of the conventional planetary roller screw 9 described above, if one of the main screw 91 or nut 92 intended to be rotated is defined as the driving part, and the other of the main screw 91 or nut 92 intended to generate linear motion is defined as the driven part, and when the main screw 91, nut 92 and multiple rollers 93 have a relatively large screw pitch, the amount of linear momentum of the driven part due to the rotation of the driving part is relatively large, resulting in a relatively high linear motion speed, and each component has a relatively large load-bearing / pressure-resistant capacity. When the main screw 91, nut 92 and multiple rollers 93 have a relatively small screw pitch, the amount of linear momentum of the driven part due to the rotation of the driving part is relatively small, resulting in a relatively low linear motion speed, which allows for precise control of the amount of movement, but the load-bearing capacity of each component is reduced.

[0005] Therefore, in applications such as electric vehicles and humanoid robots, conventional planetary roller screws 9 cannot simultaneously achieve relatively precise control of the amount of movement and a relatively large load-bearing capacity. Based on the above-mentioned problems, there is a need to further improve conventional planetary roller screws. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Taiwan Publication No. I673446 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] To solve the above problems, the object of the present invention is to provide a planetary roller screw that can significantly improve motion accuracy without reducing load-bearing pressure. [Means for solving the problem]

[0008] The terms describing directions or their approximate equivalents throughout the specification of this invention, such as "front," "back," "left," "right," "top (summit)," "bottom (bottom)," "inside," "outside," and "side," are based on the directions shown in the accompanying drawings. Each of these directions or similar terms is merely for the purpose of assisting in the explanation and understanding of each embodiment of the invention and does not limit the invention.

[0009] Throughout the specification of this invention, the counter words "one" or "one" used with respect to parts or components are used for convenience and to give a common meaning to the scope included in this invention, and should be interpreted as one or at least one in this invention, and unless explicitly stated otherwise, the concept of one also includes cases of multiple.

[0010] In the entirety of the specification of this invention, approximate terms such as "joining," "combining," or "assembling" mainly include those in which the members can be separated without damaging them even after joining, and those in which the members cannot be separated after joining, and these can be selected by a person with ordinary skill in the art according to the material of the members to be joined or the requirements of the assembly.

[0011] The planetary roller screw of the present invention includes a main screw, a nut, and a planetary unit. The main screw has a male thread extending along its outer circumference in the axial direction. The nut has a through hole that extends in the axial direction, and the nut has an internal thread that extends along the axial direction on the inner circumferential wall of the through hole, and all or part of the external thread of the main thread is located in the through hole of the nut. The planetary unit has a plurality of rollers, each of which extends along the axial direction and has a roller thread on its outer circumference, each of which is locally located at least within the through hole of the nut, and the roller thread of each of which is screwed into the male thread and the female thread, The thread pitch of the male thread of the main screw, the thread pitch of the female thread of the nut, and the thread pitch of the male thread of each roller are the same, and the helical direction of the male thread of the main screw and the helical direction of the female thread of the nut are in opposite directions. When one of the main screw, the nut, and the planetary unit is used as the driving element and the driving element is rotated, the direction of the linear motion of the planetary unit relative to the nut and the direction of the linear motion of the main screw relative to the planetary unit are opposite.

[0012] As a result, in the planetary roller screw of the present invention, the arrangement and connection relationship of the main screw, nut, and multiple rollers causes a corresponding reduction displacement when the driving part is rotated, thereby enabling precise control of the amount of movement.

[0013] The number of helical wires in the female thread of the nut is multiple, and the number of helical wires in the male thread of the main screw is also multiple. In this way, based on an implementation method in which the entire planetary roller screw typically uses a nut or main screw as the driving part, and based on the relationship that the pitch circle diameter of the roller male screw of each roller is relatively small, the number of helical wires in the female and male threads is made multiple, and by further adjusting the relationship between the pitch circle diameter, the number of helical wires and the screw pitch of the male screw, female thread and roller male screw, the expected deceleration displacement can be obtained, and the amount of movement can be precisely controlled.

[0014] Furthermore, the number of helical threads in the female thread of the nut is different from the number of helical threads in the male thread of the main screw. In this way, based on an implementation where the entire planetary roller screw typically uses a nut or main screw as the driving part, the number of helical threads is different, and by adjusting the pitch circle diameter, the number of helical threads, and the screw pitch of the male screw, female thread, and roller male screw to correspond, the expected deceleration displacement can be obtained, and in particular, a smaller deceleration displacement can be designed, and the amount of movement can be precisely controlled.

[0015] Furthermore, the helical direction of the female thread of the nut and the helical direction of the male thread of each roller are the same. In this way, either left-handed or right-handed helical direction can be selected according to the application requirements, and the characteristics of the corresponding motion can be determined.

[0016] Furthermore, the planetary unit further has an annular frame portion installed between the main screw and the nut, the annular frame portion having a plurality of housing portions, the number of which is at least the same as the number of which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are

[0017] Furthermore, the annular frame is an annular body, and each of the plurality of housings has multiple through holes in the radial direction of the annular frame. When each roller is housed in one of the plurality of housings, there is a gap on the circumference between each roller and the corresponding housing. In this way, there is a gap between each roller and the corresponding housing, which improves the smoothness of rotation between each roller, the main screw and the nut.

[0018] Furthermore, the planetary unit further has an annular frame portion installed between the main screw and the nut, the annular frame portion has two annular bodies arranged relative to each other in the axial direction, and each of the two annular bodies has a plurality of recesses that are opposite to each other in the axial direction, and the recesses are used to fit the protruding portions of each roller locally into the corresponding recesses. In this way, the arrangement of the annular frame portion allows each roller of the planetary unit to be firmly and uniformly distributed around the outer circumference of the main screw, and furthermore, when the planetary unit rotates, each roller can receive force uniformly, and furthermore, the smoothness of rotation of the planetary roller screw can be improved.

[0019] Furthermore, each of the rollers has protrusions at both ends in the axial direction, and a corresponding elastic member is installed on each of the protrusions of each roller, and each elastic member is in contact with the annular frame and the roller. In this way, each elastic member maintains a constant tension in the axial direction for each roller, thereby preventing each roller from being displaced upward in the axial direction during operation.

[0020] Furthermore, one of the tooth surfaces in the male thread of the main screw, the female thread of the nut, and the male thread of each roller is arc-shaped. In this way, the contact area between the male and female threads of the roller's male thread can be reduced, thereby reducing the corresponding frictional force, decreasing noise generation, and improving the smoothness of rotation.

[0021] Further, the female thread of the main screw further has at least one main screw tooth part, and the roller thread of each of the rollers of the planetary unit has at least one roller tooth part. When screw engagement rotation occurs between the female thread and the roller thread, meshing rotation occurs between the at least one main screw tooth part and the at least one roller tooth part. In this way, when the planetary unit rotates, each roller can be ensured to rotate in a simple rotation state, and the situation where unexpected frictional force is generated by sliding can be excluded, and furthermore, the smoothness during the rotation of the planetary roller screw can be improved.

[0022] Also, the female thread of the nut has at least one nut tooth part, and the roller thread of each of the rollers of the planetary unit has at least one roller tooth part. When screw engagement rotation occurs between the female thread and the roller thread, meshing rotation occurs between the at least one nut tooth part and the at least one roller tooth part. In this way, when the planetary unit rotates, each roller can be ensured to rotate in a simple rotation state, and the situation where unexpected frictional force is generated by sliding can be excluded, and furthermore, the smoothness during the rotation of the planetary roller screw can be improved.

Brief Description of the Drawings

[0023] [Figure 1] It is an exploded perspective view of the first embodiment of the planetary roller screw of the present invention. [Figure 2] It is a cross-sectional view of the assembled state of FIG. 1. [Figure 3] It is an enlarged view of the partial structure of area A in FIG. 2. [Figure 4] It is a schematic diagram of the motion relationship when the planetary roller screw of the present invention uses the nut as the driving part. [Figure 5] It is a schematic diagram of the motion relationship when the planetary roller screw of the present invention uses the main screw as the driving part. [Figure 6] It is a schematic diagram of the screw tooth parts of the main screw and the roller that mesh with each other. [Figure 7]This is a schematic diagram of the meshing screw teeth and spur gears of the main screw and roller. [Figure 8] This is a schematic diagram of the interlocking screw teeth of a nut and a roller. [Figure 9] This is a schematic diagram of the interlocking screw teeth and spur gears of a nut and roller. [Figure 10] This is a schematic diagram of a further preferred arrangement of the planetary unit of the planetary roller screw of the present invention. [Figure 11] Figure 10 is a schematic diagram showing that the protruding part of the roller has a corresponding elastic member. [Figure 12] This is a cross-sectional view of a conventional planetary roller screw structure. [Best Mode for Carrying Out the Invention]

[0024] To make the above-mentioned objectives, other objectives, features, and advantages of the present invention easier to understand, embodiments of the present invention are given below and will be described in more detail with reference to the drawings. Furthermore, if the same symbol is used in different drawings, it will be considered the same thing, and its explanation will be omitted.

[0025] As shown in Figures 1 and 2, a first embodiment of the planetary roller screw of the present invention includes a main screw 1, a nut 2, and a planetary unit 3. The planetary unit 3 is located inside the nut 2 and is formed to surround the main screw 1. With the above arrangement, when the nut 2 rotates axially, the planetary unit 3 can produce linear motion in the axial direction with respect to the nut 2 and the main screw 1, and the direction of the linear motion of the planetary unit 3 with respect to the nut 2 is opposite to the direction of the linear motion of the main screw 1 with respect to the planetary unit 3. Alternatively, when the main screw 1 rotates axially, the planetary unit 3 can produce relative linear motion in the axial direction with respect to the main screw 1 and the nut 2, and the direction of the linear motion of the planetary unit 3 with respect to the main screw 1 is opposite to the direction of the linear motion of the nut 2 with respect to the planetary unit 3. That is, in either case, the direction of the linear motion of the planetary unit 3 with respect to the nut 2 is opposite to the direction of the linear motion of the main screw 1 with respect to the planetary unit 3.

[0026] The outer circumference of the main screw 1 has a male thread 11 extending along the axial direction, and the helical direction of the male thread 11 may be either right-handed or left-handed. Selectively, the outer circumference of the main screw 1 may further have a connecting portion 12, and preferably, the male thread 11 can be installed at one end closer to the main screw 1, and the connecting portion 12 can be installed at the other end closer to the main screw 1. Furthermore, in order to clearly explain the directional arrangement in the present invention, the main screw 1 can be defined as having a central axis C, and the direction extending from the central axis C can be defined as the "axial direction" as described in the entire text of the present invention.

[0027] The nut 2 has a through hole 20 extending in the axial direction, and the nut 2 has an internal thread 21 extending axially along the inner circumferential wall of the through hole 20. The helical direction of the internal thread 21 may be either right-handed or left-handed. In particular, the helical direction of the internal thread 21 and the helical direction of the external thread 11 are opposite. At least a portion of the main thread 1 is located within the through hole 20 of the nut 2. In particular, all or part of the external thread 11 of the main thread 1 is located within the through hole 20 of the nut 2. In other words, all or part of the external thread 11 is aligned with the internal thread 21 in the radial direction.

[0028] Preferably, the planetary unit 3 has a plurality of rollers 31 and further has an annular frame portion 32. Each roller 31 extends along the axial direction, and the outer circumference of each roller 31 has a roller thread 311, and the spiral direction of the roller thread 311 may be either right-handed or left-handed. In particular, the spiral direction of the roller thread 311 and the spiral direction of the female thread 21 of the nut 2 are the same, that is, the spiral direction of the roller thread 311 and the spiral direction of the male thread 11 of the main screw 1 are opposite. At least a portion of each roller 31 is located inside the through hole 20 of the nut 2, and the roller thread 311 of each roller 31 is screwed into the male thread 11 and the female thread 21, respectively. Preferably, each roller 31 is uniformly distributed around the outer circumference of the main screw 1 according to its number. For example, if the number of plurality of rollers 31 is N, each roller 31 surrounds the outer circumference of the main screw 1 at equal angular intervals (360° divided by N). N is a positive integer greater than 1, and more preferably a number that divides 360° evenly.

[0029] Preferably, the planetary unit 3 further has a corresponding annular frame 32, which is installed between the main screw 1 and the nut 2 and has a plurality of housing sections 320, the number of which is at least the same as the number of which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are which are

[0030] In the embodiment shown in Figure 1 of the present invention, the annular frame portion 32 is formed as an annular body by extending from an annular shape having a central through-hole in the axial direction, and each of the multiple housing portions 320 has multiple through-holes that correspond to each other in the radial direction of the annular frame portion 32, and each through-hole has a contour corresponding to a roller 31, so that each roller 31 can be housed in one of the corresponding housing portions 320. For example, when each roller 31 is housed in one of the corresponding housing portions 320, there is a suitable distance on the circumference between each roller 31 and the corresponding housing portion 320, which can help in the rotation between each roller 31 and the main screw 1 / male screw 11 and the nut 2 / female screw 21. In this way, the arrangement of the multiple housing portions 320 of the annular frame portion 32 not only allows for easy installation of multiple rollers 31 between the main screw 1 and the nut 2, but also ensures that the position of each roller 31 between the main screw 1 and the nut 2 is firmly established, making displacement less likely.

[0031] Selectively, each roller 31 has projections 312 at both ends in the axial direction, the projections 312 extending outward from the corresponding roller 31 along the axial direction (particularly the central axis of the roller 31), and the diameter of the projections 312 is not larger than the diameter of the roller 31, preferably smaller than the diameter of the roller 31. In this way, when each roller 31 is installed in the corresponding housing 320, and when each roller 31 comes into contact with the annular frame 32 in the axial direction, each roller 31 comes into contact with the annular frame 32 (at the position of the edge corresponding to the housing 320) by its projection 312, thus reducing the frictional force when each roller 3 rotates within the housing 320.

[0032] Due to the arrangement / connection relationship between the main screw 1, nut 2, and planetary unit 3 described above, when the nut 2 rotates axially, the planetary unit 3 / each roller 31 can perform linear motion relative to the nut 2 and main screw 1 in the axial direction. Alternatively, when the main screw 1 rotates axially, the nut 2 and the planetary unit 3 / each roller 31 can perform linear motion relative to the main screw 1 and nut 2 in the axial direction. Similarly, when the planetary unit 3 rotates axially, the main screw 1 and nut 2 can also perform linear motion relative to the planetary unit 3 in the axial direction, and the main screw 1 performs linear motion relative to the nut 2. In other words, by arranging the planetary roller screw in the present invention, when any one of the main screw 1, nut 2, and planetary unit 3 rotates axially as the driving part, the direction of linear motion of the planetary unit 3 relative to the nut 2 is opposite to the direction of linear motion of the main screw 1 relative to the planetary unit 3, so a deceleration displacement occurs, achieving precise motion control.

[0033] More specifically, as shown in Figure 3, in order to realize the deceleration displacement mechanism described above, the screw pitch P1 of the male screw 11, the screw pitch P2 of the female screw 21, and the screw pitch P3 of the roller male screw 311 are the same.

[0034] Preferably, the tooth surface (Flank) 311F of the roller male screw 311 is arc-shaped, which reduces the contact area between the roller 31 and the male thread 11 and female thread 21 of the roller male screw 311, thereby reducing the frictional force between the male thread 11 and female thread 21 of the roller male screw 311, thus reducing noise generation and improving rotational smoothness. It should be noted that in other examples, it is possible to selectively make one of the tooth surfaces 11F of the male thread 11, the tooth surface 21F of the female thread 21, and the tooth surface 311F of the roller male screw 311 arc-shaped, but the present invention is not limited thereto.

[0035] Of particular note is that, as shown in Figures 1 to 3, the height at which each roller 31 is positioned axially between the main screw 1 and the nut 2 varies based on the lead angle of the main screw 1 and the nut 2, and the position (with a relative angle difference) at which each roller 31 is distributed on the circumference of the main screw 1 and the nut 2. In one example, each housing portion 320 of the annular frame 32 can be configured to accommodate the aforementioned change in the axial height of each roller 31 by forming a through-hole height H greater than the length L of each roller 31 in the axial direction, and a gap G (as shown in Figures 4 and 5) is formed, and the height H of the through-hole is longer than the length L of each roller 31 (not less than 0.5 screw pitches P3), preferably not less than 1 screw pitch P3. Optionally, in another example (not shown), the axial height position of each housing portion 320 of the annular frame 32 can be changed according to actual requirements to allow each roller 31 to be easily installed between the main screw 1 and the nut 2. Alternatively, in another example (not shown), while keeping the arrangement of the axial height positions of each housing 320 unchanged, the axial length of the protrusions 312 at both ends of each roller 3 can be varied so that when each roller 3 is installed in the corresponding housing 320, it has a corresponding height suitable for positioning in the axial direction for the main screw 1 and / or nut 2.

[0036] More specifically, as shown in Figure 4, in order to further clarify the motion mechanism of the planetary roller screw of the present invention, and in particular to explain the relationship between the rotational direction and the linear motion direction between each member, the male thread 11 of the main screw 1 is defined to have opposing threaded tops 11a and threaded bottoms 11b in the axial direction, the nut 2 has opposing nut tops 2a and nut bottoms 2b in the axial direction, and each roller 3 has opposing roller tops 31a and roller bottoms 31b in the axial direction. The threaded tops 11a, nut tops 2a and roller tops 31a are defined as the first direction, and the threaded bottoms 11b, nut bottoms 2b and roller bottoms 31b are defined as the second direction.

[0037] In the example shown in Figure 4, the helical direction of the female thread 21 of the nut 2 and the helical direction of the roller male thread 311 of the roller 31 are all right-handed, while the helical direction of the male thread 11 of the main screw 1 is left-handed. Furthermore, taking a viewpoint from the bottom end 2b of the nut toward the top end 2a of the nut, the central axis C of the main screw 1 rotates clockwise (i.e., in the same direction as the helical direction of the nut 2) with the nut 2 as the driving force. The female thread 21 revolves around the central axis C of the main screw 1 in the same direction (clockwise) in conjunction with each roller 31 and the nut 2. At this time, the multiple rollers 31 / planetary unit 3 as a whole undergo linear motion relative to the nut 2 in the axial direction, and the multiple rollers 31 also undergo linear motion in the second direction (i.e., the direction toward the bottom end 2b of the nut).

[0038] Next, due to the connection relationship in which the helical direction of the roller male thread 311 of each roller 31 is opposite to the helical direction of the male thread 11 of the main thread 1, the multiple rollers 31 as a whole undergo linear motion relative to the main thread 1 in the axial direction, and the main thread 1 undergoes linear motion relative to the first direction / direction of the top end 11a of the threaded portion. It is particularly important to note that, due to the above arrangement, the main thread 1 can only undergo linear motion in the axial direction, so no rotational motion occurs on the circumference, and the direction of linear motion of the planetary unit 3 relative to the nut 2 is opposite to the direction of linear motion of the main thread 1 relative to the planetary unit 3.

[0039] Based on the arrangement and motion relationship shown in Figure 4, we further define a first distance d1 between the top of the threaded portion 11a and the top of the roller 31a, and a second distance d2 between the top of the roller 31a and the bottom of the nut 2b. When the main screw 1 moves in the first direction, the first distance d1 increases, and simultaneously, when each roller 31 moves in the second direction, the second distance d2 decreases. Since the main screw 1 is installed in the planetary unit 3 formed by each roller 31, a decelerated displacement occurs in the axial direction between the main screw 1 and the nut 2. This decelerated displacement can be defined by the difference in the front-to-back distance due to the motion between the top of the threaded portion 11a and the top of the nut 2a, and 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.

[0040] Similarly, based on the arrangement and motion relationship shown in Figure 4, when the nut 2 rotates counterclockwise, the main screw 1 moves linearly in the second direction, so the first distance d1 becomes shorter, and the multiple rollers 31 move linearly in the first direction, so the second distance d2 becomes longer, and similarly a deceleration displacement can occur in the axial direction between the main screw 1 and the nut 2.

[0041] In another example, as shown in Figure 5, the arrangement in Figure 4 is used again, but instead the main screw 1 is used as the driving force, and the central axis C of the main screw 1 is rotated counterclockwise. The male screw 11 revolves around the central axis C of the main screw 1 in the same direction (counterclockwise), with each roller 31 linked to the main screw 1. At this time, the multiple rollers 31 as a whole undergo linear motion relative to the main screw 1 in the axial direction, and the multiple rollers 31 also undergo linear motion in the second direction (i.e., the direction of the nut bottom end 2b).

[0042] Next, due to the connection relationship in which the helical direction of the roller male thread 311 of each roller 31 and the helical direction of the female thread 21 of the nut 2 are the same, the multiple rollers 31 / planetary unit 3 as a whole undergo linear motion relative to the nut 2 in the axial direction, and the nut 2 undergoes linear motion relative to the first direction (i.e., the direction of the top end 11a of the threaded portion). It is particularly important to note that, due to the above arrangement, the nut 2 can only undergo linear motion in the axial direction, and therefore does not undergo rotational motion on the circumference, and the direction of linear motion of the planetary unit 3 relative to the main thread 1 is opposite to the direction of linear motion of the nut 2 relative to the planetary unit 3.

[0043] Based on the arrangement and motion relationship shown in Figure 5, the nut 2 can be considered to be installed in a planetary unit 3 formed by each roller 31. When multiple rollers 31 move in the second direction, the first distance d1 increases, and at the same time, when the nut 2 moves in the first direction, the second distance d2 decreases. Since the nut 2 is installed in a planetary unit 3 formed by each roller 31, the aforementioned deceleration displacement occurs in the axial direction between the main screw 1 and the nut 2.

[0044] Based on the arrangement and motion relationship shown in Figure 5, when the main screw 1 rotates clockwise, the multiple rollers 31 move linearly in the first direction, so the first distance d1 becomes shorter. When the nut 2 moves linearly in the second direction, the second distance d2 becomes longer, and similarly, a deceleration displacement in the axial direction can be generated between the main screw 1 and the nut 2.

[0045] It should be noted that, based on the mechanism of the planetary roller screw of the present invention, the helical direction of the female thread 21 and the roller male thread 311 is the same, while the helical direction of the male thread 11 is in the opposite direction. Therefore, the helical direction of the female thread 21 and the roller male thread 311 of the planetary roller screw of the present invention described above is right-handed, and the helical direction of the male thread 11 is left-handed. That is, the arrangement of the members can be considered as "nut 2 - roller 31 - main thread 1" from outside to inside, and the corresponding helical direction can be shown as "right-right-left". However, the present invention naturally includes an arrangement in which the helical direction of the female thread 21 and the roller male thread 311 is left-handed, and the helical direction of the male thread 11 is right-handed. The corresponding helical direction can be shown as "left-left-right", and the rotational direction and linear motion direction of each member in the aforementioned "left-left-right" arrangement and the aforementioned "right-right-left" arrangement are opposite.

[0046] Of particular note is that, according to the arrangement of the planetary roller screw of the present invention shown in Figures 1 to 3, and furthermore, the motion mechanism shown in Figures 5 and 6, the planetary roller screw of the present invention can generate deceleration displacement regardless of whether either the main screw 1 or the nut 2 is the driving part and rotates around the axis. Furthermore, it can reduce the relative displacement between the main screw 1 and the nut 2 under the same or approximate screw pitch arrangement conditions as the conventional technology, thereby achieving more precise motion control. In addition, since the corresponding screw pitch arrangement conditions of the main screw 1, nut 2, and roller 31 are maintained in their original state (not more tightly adjusted), the main screw 1, nut 2, and roller 31 can maintain similar load-bearing capacity without increasing the corresponding processing costs. In other words, compared to the conventional technology shown in Figure 12, when seeking control with similar displacement accuracy, i.e., when the driven part has the same displacement when the driving part completes one rotation, the screw pitch of the present invention can be made even larger, resulting in better load-bearing capacity and further saving on manufacturing costs.

[0047] Another point to note is that in Figures 4 and 5, the nut 2 and the main screw 1 are used as the driving parts, respectively. However, based on the motion mechanism of the planetary roller screw of the present invention, the planetary unit 3 can also be used as the driving part, and the nut 2 and the main screw 1 can each be made to move linearly relative to the planetary unit 3 in the axial direction. In this case, the planetary unit 3 is considered to be fixed and immovable, but the linear motion of the nut 2 relative to the planetary unit 3 can also be considered as the linear motion of the planetary unit 3 relative to the nut 2, and therefore still conforms to the motion mechanism described above. The direction of the linear motion of the planetary unit 3 relative to the nut 2 (in this case, the nut 2 is considered to be fixed, and the direction of motion of the planetary unit 3 relative to this fixed object is observed) is opposite to the direction of the linear motion of the main screw 1 relative to the planetary unit 3 (in this case, the planetary unit 3 is considered to be fixed, and the direction of motion of the main screw 1 relative to this fixed object is observed).

[0048] Another point to note is that the relationship between the first distance d1, the second distance d2, and the numerical values ​​of the reduction displacement described above, and the pitch circle diameter, number of threads, and thread pitch of the male screw 11, female screw 21, and roller male screw 311, respectively, is interdependent. Preferably, the conditions such as the pitch circle diameter, number of threads, and thread pitch are designed based on the principles of motion in screw threading that are understandable to those skilled in the art, thereby realizing the motion relationship and precision requirements between the main screw 1, nut 2, and roller 31. In particular, the product of the number of threads and thread pitch described above is the lead, meaning that the arrangement of the motion conditions described above can be considered to be related to the pitch circle diameter and the lead.

[0049] Preferably, the number of helical wires in the female thread 21 of the nut 2 is multiple, and the number of helical wires in the male thread 11 of the main thread 1 is also multiple, and the number of helical wires in the female thread 21 of the nut 2 and the number of helical wires in the male thread 11 of the main thread 1 can be selected to be the same or different. In this way, based on an implementation in which the entire planetary roller screw is normally driven by the nut 2 or the main thread 1, and based on the relationship that the pitch circle diameter of the roller male thread 311 of each roller 31 is relatively small, the number of helical wires in the female thread 21 and the male thread 11 is made multiple, and by further adjusting the relationship between the pitch circle diameter, the number of helical wires and the screw pitch of the male thread 11, female thread 21 and roller male thread 311 to correspond, the expected deceleration displacement can be obtained, and thus precise motion control can be performed.

[0050] In particular, in one example, the number of helical threads in the female thread 21 of nut 2 may be 5, the number of helical threads in the male thread 11 of main thread 1 may be 4, and the number of helical threads in the roller male thread 311 may be 1. Thus, based on the implementation method in which the entire planetary roller screw typically uses either the nut 2 or the main screw 1 as the driving force, and based on the relationship that the pitch circle diameter of the roller male screw 311 of each roller 31 is relatively small, and further based on the relationship that the pitch circle diameter of the female screw 21 of the nut 2 is larger than the pitch circle diameter of the male screw 11 of the main screw 1, the number of helical wires of the female screw 21 and the number of helical wires of the male screw 11 are different, in particular the number of helical wires of the female screw 21 is greater than the number of helical wires of the male screw 11, and the number of helical wires of the roller male screw is set to 1, and further by adjusting the relationship between the pitch circle diameter, the number of helical wires and the screw pitch of the male screw 11, female screw 21 and roller male screw 311 to correspond, it is possible to design a relatively small reduction displacement more easily, and thus precise motion control can be achieved.

[0051] It should be noted that the number of helical wires in the female thread 21, male thread 11, and roller male thread 311 is not limited to those stated above. Additionally, the roller male thread 311 may have multiple helical wires. Furthermore, the number of helical wires in the female thread 21 and / or male thread 11 may also be just one.

[0052] In particular, in one specific embodiment, when the pitch circle diameter, number of helical wires, screw pitch, and helical direction of the male screw 11, female screw 21, and roller male screw 311 are formed in a specific arrangement, and the pitch circle diameter of the male screw 11 is an integer multiple of the pitch circle diameter of the roller male screw 311, and when the nut 2 is rotated with the nut 2 as the driving force, no relative displacement occurs between each roller 31 and the main screw 1. In such a specific arrangement, if the pitch circle diameter of the male screw 11 and the pitch circle diameter of the roller male screw 311 are not integer multiples, then when the nut 2 is rotated with the nut 2 as the driving force, relative displacement occurs between each roller 31 and the main screw 1.

[0053] As shown in Figures 6 and 7, preferred arrangements of the main screw 1 and each roller 31 in the planetary roller screw of the present invention are shown. Compared with Figures 1 to 3, the main screw 1 further has at least one main screw tooth 1G. Each roller 31 also has at least one roller tooth 31G, and when screwed rotation occurs between the male screw 11 and the roller male screw 311, meshing rotation occurs between at least one main screw tooth 1G and at least one roller tooth 31G. Furthermore, the meshing rotation of at least one main screw tooth 1G and at least one roller tooth 31G ensures that each roller 31 rotates in a simple rotational state when the planetary unit 3 rotates (revolves around the main screw 1 of each roller 31), eliminating situations where unexpected frictional forces are generated by sliding, and further improving the smoothness of the rotation of the planetary roller screw.

[0054] In the embodiment shown in Figure 6, the main screw 1 has a single row of main screw teeth 1G that are arranged over the entire area of ​​the male screw 11. However, in other embodiments (not shown), the main screw teeth 1G may be arranged in a single row or multiple rows in one or more local areas of the male screw 11 or the main screw 1. Each roller 31 has two rows of roller teeth 31G that are arranged in local areas of the roller male screw 311 that are close to both ends of the roller 31 in the axial direction (i.e., the roller top end 31a and the roller bottom end 31b). However, in other embodiments (not shown), the roller teeth 31G may be arranged in a single row that are arranged over the entire area of ​​the roller male screw 311, or in a single row or multiple rows in one or more local areas of the roller male screw 311 or the roller 31. In particular, the main screw teeth 1G consist of multiple concave or protruding structures formed on the male thread 11, and the roller teeth 31G are used to mesh with the main screw teeth 1G and consist of multiple concave or protruding structures formed on the roller male thread 311 of each roller 31.

[0055] In the embodiment shown in Figure 7, the main difference from Figure 6 is that the main screw 1 further has another stage of main screw teeth 1G located at one of the outer ends in the axial direction of the male screw 11, and this other stage of main screw teeth 1G has a spur gear structure. One of the two stages of roller teeth 31G is located at one of the outer ends in the axial direction of the roller male screw 311, and since the roller teeth 31G has a spur gear structure, it meshes with the spur gear structure in the two stages of main screw teeth 1G. It should be noted that in the embodiment shown in Figure 7, the main screw teeth 1G and roller teeth 31G having a spur gear structure are located corresponding to the outer positions of the bottom end 11b of the screw and the bottom end 31b of the roller, respectively, but in other embodiments, they can also be located corresponding to the outer positions of the top end 11a of the screw and the top end 31a of the roller, respectively. In other embodiments (not shown), for example, when arranging the main screw teeth 1G of a spur gear structure, the male screw 11 can be placed between the two stages of main screw teeth 1G by arranging them in a two-stage manner at the outer positions of both ends of the male screw 11 of the main screw 1. For example, when arranging the roller teeth 31G of a spur gear structure, the roller male screw 311 can be placed between the two stages of roller teeth 31G by arranging them in a two-stage manner at the outer positions of both ends of the roller male screw 311 of the roller 31.

[0056] As shown in Figures 6 and 7, another better arrangement of the nut 2 and each roller 31 in the planetary roller screw of the present invention is shown in Figures 8 and 9. The nut 2 also has at least one nut tooth 2G. Each roller 31 further has at least one roller tooth 31G, so when screw rotation occurs between the female thread 21 and the roller male thread 311, meshing rotation occurs simultaneously between at least one nut tooth 2G and at least one roller tooth 31G. Furthermore, the meshing rotation of at least one nut tooth 2G and at least one roller tooth 31G ensures that each roller 31 rotates in a simple rotational state when the planetary unit 3 rotates (each roller 31 revolves around the main thread 1), eliminating situations where unexpected frictional forces are generated by sliding, and further improving the smoothness of the rotation of the planetary roller screw.

[0057] In the embodiment shown in Figure 8, the nut 2 has a single row of nut teeth 2G that are arranged over the entire area of ​​the female thread 21. However, in other embodiments (not shown), the nut teeth 2G may be arranged in a single row or in multiple rows, respectively, in one or more local areas of the female thread 21 or the nut 2. Each roller 31 has two rows of roller teeth 31G that are arranged over local areas of the roller thread 311 as the roller 31 approaches both ends in the axial direction (i.e., the roller top end 31a and the roller bottom end 31b). However, in other embodiments (not shown), the roller teeth 31G may be arranged in a single row that covers the entire area of ​​the roller thread 311, or in a single row or in multiple rows, respectively, in one or more local areas of the roller thread 311 or the roller 31.

[0058] In the embodiment shown in Figure 9, the main difference from Figure 8 is that the nut 2 further has another stage of nut teeth 2G located at one of the outer positions on either end in the axial direction of the female thread 21, and this other stage of nut teeth 2G has a spur gear structure. One of the two stages of roller teeth 31G is located at one of the outer positions on either end in the axial direction of the roller male thread 311, and since the roller teeth 31G has a spur gear structure, it meshes with the spur gear structure in the two stages of nut teeth 2G. It should be noted that in the nut teeth 2G and roller teeth 31G with spur gear structures shown in Figure 9, they are positioned corresponding to the outer positions of the nut bottom end 2b and the roller bottom end 31b, respectively, but in other embodiments, they can also be positioned corresponding to the outer positions of the nut top end 2a and the roller top end 31a, respectively. In other embodiments (not shown), for example, when arranging the nut teeth 2G of a spur gear structure, the female thread 21 can be placed between the two stages of nut teeth 2G by arranging them in a two-stage manner at the outer positions of both ends of the female thread 21 of the nut 2. For example, when arranging the roller teeth 31G of a spur gear structure, the roller male thread 311 can be placed between the two stages of roller teeth 31G by arranging them in a two-stage manner at the outer positions of both ends of the roller male thread 311 of the roller 31.

[0059] It should be noted that, based on Figures 6 to 9, the "teeth" of the present invention can be positioned on the main screw 1 and each roller 31, or on the nut 2 and each roller 31, or on the main screw 1, nut 2 and each roller 31, so that each roller 31 forms a motion pattern of simple rotation relative to the main screw 1 and nut 2. The teeth mentioned above refer to the main screw teeth 1G, nut teeth 2G, and roller teeth 31G. In particular, the position and area / range in which the teeth mentioned above are positioned on the main screw 1, nut 2, and each roller 31 can be set based on the range of motion between the main screw 1, nut 2, and each roller 31. In particular, when forming the characteristics of the corresponding teeth, the corresponding pitch circle diameters for the male screw 11, female screw 21, and roller male screw 311 must be considered, and it is preferable that the smallest of these pitch circle diameters divides the others evenly.

[0060] Another point to note is that while the teeth shown in Figures 7 and 9 of this invention utilize a spur gear structure to achieve meshing rotation in the parallel axis direction, this invention is not limited to spur gears and includes other structures for meshing rotation in the parallel axis direction.

[0061] Furthermore, another better arrangement of the planetary unit 3 in the planetary roller screw of the present invention is shown in Figure 10. The annular frame portion 32 of the planetary unit 3 has two annular bodies 321 arranged relative to each other in the axial direction, and the two annular bodies 321 each have a plurality of recesses 321C that are opposite to each other in the axial direction, and the recesses 321C are used to fit the protrusions 312 of each roller 31 into the locally corresponding recesses 321C. In particular, each roller 31 can have the structure shown in Figures 1, 6 to 9. It should be noted that although the recesses 321C shown in Figure 11 of the present invention are through holes, the structure of the recesses 321C is not limited to this. For example, the recesses 321C can be formed as a concave shape and not a through hole.

[0062] As selectable, as shown in Figure 11, a corresponding elastic member E is installed on the protrusion 312 of the rotor 31, and each elastic member E is in contact with the annular frame 32 and the roller 31. In this way, each elastic member E maintains a constant tension in the axial direction on each roller 31, thereby preventing each roller 31 from being displaced in the axial direction during operation. Preferably, the elastic member E described above can be in the form of a coil spring.

[0063] According to the arrangement and motion mechanism of the planetary roller screw of the present invention described above, one of the main screw 1, nut 2, and planetary unit 3 can be designated as the driving part, and the other two of the main screw 1, nut 2, and planetary unit 3 can be designated as the driven parts. When the driving part is rotated, the direction of the linear motion of the planetary unit 3 relative to the nut 2 is opposite to the direction of the linear motion of the main screw 1 relative to the planetary unit 3. Furthermore, the motion relationship and precision requirements between the main screw 1, nut 2, and roller 31 can be achieved by adjusting the pitch circle diameter, the number of helical wires, and the screw pitch conditions of the main screw 1, nut 2, and roller 31, respectively.

[0064] In summary, the planetary roller screw of the present invention achieves precise motion control by generating a deceleration displacement between the main screw and the nut, as the helical directions of the female thread of the nut and the male thread of the roller are in the same direction, while the helical direction of the male thread of the main screw is in the opposite direction. In particular, due to the motion relationship between the driving part and the driven part in the planetary roller screw of the present invention, the planetary roller screw of the present invention can be applied in various situations where precise linear motion control is required, replacing hydraulic cylinders in various machine tools, brake devices, robots, and the like.

[0065] Although the present invention has been disclosed with the above embodiments, they do not limit the invention. Those skilled in the art will know that various modifications to the above embodiments will remain within the scope of the invention, as long as they do not depart from the spirit and scope of the invention. Accordingly, the scope of the invention includes all modifications that fall within the scope of the language set forth in the claims and equivalents described below. Furthermore, where the above embodiments can be combined, the present invention includes any combined embodiments. [Explanation of Symbols]

[0066] 1 Main screw 11 male thread 11a Top of threaded portion 11b Bottom end of threaded portion 11F Tooth surface 1G Main thread teeth 12 Connecting part 2 nuts 2a Nut top 2b Nut bottom end 2G Nut Teeth 20 Through holes 21 Female thread 21F Tooth surface 3 Planetary Units 31 Laura 31G Roller Teeth 31a Roller top end 31b Roller bottom end 311 Roller male screw 311F Tooth surface 312 Protrusion 32 Ring frame section 320 Storage Unit 321 Ring-shaped body 321C recess C center axis d1 first distance d2 second distance E Elastic member G Gap H Height L Length 9 Planetary roller screw 91 Main screw 911 Male thread 92 Nuts 921 Female thread 922 Threadless part 93 Laura 931 Roller male screw 932 External thread section 94 Shaft Ring 941 Internal annular thread 95 Fixed plate

Claims

1. Includes main screw, nut and planetary unit, The main screw has a male thread extending along its outer circumference in the axial direction. The nut has a through hole that extends in the axial direction, and the nut has an internal thread that extends along the axial direction on the inner circumferential wall of the through hole, and all or part of the external thread of the main thread is located in the through hole of the nut. The planetary unit has a plurality of rollers, each of which extends along the axial direction and has a roller thread on its outer circumference, each of which is locally located at least within the through hole of the nut, and the roller thread of each of which is screwed into the male thread and the female thread, The thread pitch of the male thread of the main screw, the thread pitch of the female thread of the nut, and the thread pitch of the male thread of each roller are the same, and the helical direction of the male thread of the main screw and the helical direction of the female thread of the nut are in opposite directions. A planetary roller screw characterized in that one of the main screw, the nut, and the planetary unit is the driving part, and when the driving part is rotated, the direction of linear motion of the planetary unit relative to the nut and the direction of linear motion of the main screw relative to the planetary unit are opposite.

2. The planetary roller screw according to claim 1, characterized in that the number of helical wires in the female thread of the nut is multiple, and the number of helical wires in the male thread of the main screw is multiple.

3. The planetary roller screw according to claim 2, characterized in that the number of helical wires in the female thread of the nut is different from the number of helical wires in the male thread of the main screw.

4. The planetary roller screw according to claim 1, characterized in that the helical direction of the female thread of the nut and the helical direction of the male thread of each roller are the same.

5. The planetary unit further comprises an annular frame portion installed between the main screw and the nut, the annular frame portion having a plurality of housing portions, the number of the plurality of housing portions being at least the same as the number of the plurality of rollers, and each of the rollers being housed in a corresponding one of the plurality of housing portions, as described in any one of claims 1 to 4.

6. The planetary roller screw according to claim 5, characterized in that the annular frame portion is an annular body, each of the plurality of housing portions forms a plurality of through holes in the radial direction of the annular frame portion, and when each of the rollers is housed in one of the plurality of housing portions, there is a gap on the circumference between each of the rollers and the corresponding housing portion.

7. The planetary roller screw according to any one of claims 1 to 4, wherein the planetary unit further has an annular frame portion installed between the main screw and the nut, the annular frame portion has two annular bodies arranged relative to each other in the axial direction, each of the two annular bodies has a plurality of recesses that are opposite to each other in the axial direction, and the recesses are used to fit the projections of each roller locally into the corresponding recesses.

8. The planetary roller screw according to claim 7, characterized in that each of the rollers has a projection at both ends in the axial direction, a corresponding elastic member is installed on each of the projections of each roller, and each of the elastic members is in contact with the annular frame and the roller.

9. The planetary roller screw according to any one of claims 1 to 4, characterized in that one of the tooth surfaces in the male thread of the main screw, the female thread of the nut, and the roller male thread of each roller is arc-shaped.

10. The planetary roller screw according to any one of claims 1 to 4, wherein the male thread of the main screw further has at least one main screw tooth, and the male roller thread of each of the rollers of the planetary unit has at least one roller tooth, and when screw rotation occurs between the male thread and the roller male thread, meshing rotation occurs between the at least one main screw tooth and the at least one roller tooth.

11. The planetary roller screw according to any one of claims 1 to 4, characterized in that the female thread of the nut has at least one nut tooth, the male thread of each roller of the planetary unit has at least one roller tooth, and when screw rotation occurs between the female thread and the male roller, meshing rotation occurs between the at least one nut tooth and the at least one roller tooth.

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