Planetary roller screw

Abstract

Conventional planetary roller screws have the problem of insufficient structural strength when controlled by precision motion, and this solves that problem. [Solution] The invention includes a main screw, a nut, and a planetary unit, the main screw having a first male screw, the nut having a female screw, and the planetary unit having a plurality of rollers, each roller having a second male screw, the helical direction of the first male screw and the helical direction of the female screw being opposite, the helical direction of the female screw and the helical direction of the second male screw being the same, the ratio of the pitch circle diameters between the passive parts being the same, and the number of helical wires of the nut not being equal to the sum of the number of helical wires of the main screw and the number of helical wires of the two rollers. Based on this, when the driving part is rotated, the driving part causes relative axial displacement with respect to each passive part, and does not cause relative axial displacement between the passive parts. The present invention makes it possible to maintain precise motion and increase the strength of the structure.

Description

[Technical Field]

[0001] This invention relates to the technology of linear parallel motion, and more particularly to planetary roller screws. [Background technology]

[0002] With advancements in industrial technology, particularly in the development of electric vehicles and humanoid robots, planetary roller screws are being used to control linear parallel motion. Because they can withstand high loads, have high positioning accuracy, and move at high speeds, they can replace conventional hydraulic mechanisms.

[0003] As shown in Figure 12, a conventional planetary roller screw 9 has multiple rollers 93 between a main screw 91 and a nut 92. The main screw 91 has a first male thread 911, the nut 92 has a female thread 921, and the multiple rollers 93 form a planetary unit similarly and jointly with each other. Each of the multiple rollers 93 has a second male thread 931, and by rotating the main screw 91 as the driving force, the rollers 93 and the nut 92 move together along the axial direction of the main screw 91.

[0004] Based on the movement mechanism of the conventional planetary roller screw 9 described above, one of the main screw 91 or the nut 92 to be rotated is defined as the driving part, and the other of the main screw 91 or the nut 92 to generate linear motion is defined as the driven part. When the main screw 91, the nut 92, and the plurality of rollers 93 have a relatively large screw pitch, the linear momentum of the driven part due to one rotation of the driving part is relatively large, so it has a relatively high linear motion speed, and each member has a relatively large load-bearing / pressure-resistant capacity. When the main screw 91, the nut 92, and the plurality of rollers 93 have a relatively small screw pitch, the linear momentum of the driven part due to one rotation of the driving part is relatively small and has a relatively low linear motion speed, so the momentum can be accurately controlled, but the load-bearing capacity of each member decreases as the screw pitch decreases. Therefore, in the applications of electric vehicles and humanoid robots, the conventional planetary roller screw 9 cannot simultaneously achieve relatively accurate momentum control and relatively large load-bearing capacity.

[0005] Also, in the conventional technology, the number of threads T 91 of the main screw 91 93 is required to be the number obtained by multiplying the number of threads T 91 of the roller 93 by the pitch circle diameter pitch D 93 of the main screw 91 and dividing by the pitch circle diameter D 91 of the roller 93, that is, the corresponding formula is T 93 = T 91 (D 93 / D 92 ) and can be expressed as such. Further, at the same time, the number of threads T 91 of the nut 92 93 is limited to be the number obtained by adding the number of threads T 92 of the main screw 91 to the number of threads T 91 of two rollers 93, that is, the corresponding formula is T 93 = T

[0006] Specifically, under the limiting conditions according to the above design rules, the pitch circle diameter D of the nut 92 92 is the pitch circle diameter D of the main screw 91 91and the pitch circle diameter D of the two rollers 93 93 It must be equal to the sum of, that is, the corresponding expression is D 92 =D 91 +2D 93 It can be defined as follows. Thus, the conventional dimensional standard can be estimated as follows: [Pitch circle diameter D of main thread 91] 91 and the pitch circle diameter D of roller 93 93 The ratio of the main screw 91 is the number of helical wires T 91 And the number of spirals T of the roller 93 93 The ratio is equal to the number of helical wires of the nut 92, and T 92 The number of helical threads T of the main screw 91 91 The number of spirals T of the two rollers 93 93 It is equal to the sum of, that is, the corresponding expression is D 91 / D 93 =T 91 / T 93 , and T 92 =T 91 +2T 93 It can be expressed as follows.

[0007] However, when the planetary roller 9 manufactured according to the above design rules actually rotates the drive unit, sliding and slippage are likely to occur between the main screw 91, roller 93, and nut 92, making it impossible to effectively produce the expected rotation-to-output stroke ratio.

[0008] Based on the problems described above, it is necessary to further improve conventional planetary roller screws. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Taiwan Publication No. I673446 [Overview of the project] [Problems that the invention aims to solve]

[0010] In order to solve the above problems, the first object of the present invention is to provide a planetary roller screw that can significantly improve the motion accuracy without reducing the load-bearing pressure.

[0011] The second object of the present invention is to provide a planetary roller screw that can achieve stable motion control.

Means for Solving the Problems

[0012] The terms of direction or their approximate terms described throughout the specification of the present invention, such as "front", "rear", "left", "right", "upper (top)", "lower (bottom)", "inner", "outer", "side surface", etc. are based on the directions on the attached drawings, and each term of direction or their approximate terms are only for assisting the description and understanding of each embodiment of the present invention, and do not limit the present invention.

[0013] Throughout the specification of the present invention, the numeral words such as "one" or "a" used for parts or components are used for convenience and give the normal meaning to the scope included in the present invention, and should be interpreted as one or at least one in the present invention. Unless clearly indicating another meaning, the concept of one also includes the case of multiple.

[0014] Throughout the specification of the present invention, approximate terms such as "coupling", "combination" or "assembly" mainly include those that can be separated without destroying the members even after being connected, and those that cannot be separated after being connected. This can be selected by those with ordinary knowledge in this technical field according to the material of the members to be connected or the requirements of assembly.

[0015] The planetary roller screw of the present invention includes a main screw, a nut and a planetary unit. The main screw has a first thread formed on its outer periphery extending along the axial direction. The nut has a through hole extending in the axial direction, and a female thread extending along the axial direction is formed on the inner peripheral wall of the through hole of the nut. All or part of the first thread of the main thread is located in the through hole of the nut. The planetary unit has a plurality of rollers. Each roller extends along the axial direction, and a second thread is provided on the outer periphery of each roller. Each roller is at least partially located in the through hole of the nut, and the second thread of each roller is screwed with the first thread and the female thread respectively. The thread pitch of the first thread, the thread pitch of the female thread, and the thread pitch of the second thread are the same. The helix direction of the first thread and the helix direction of the female thread are opposite, and the helix direction of the female thread and the helix direction of the second thread are the same. One of the main thread or the nut is defined as the driving part, and the other two of the main thread, the nut and the planetary unit that are not the driving part are defined as the driven parts respectively. Based on the arrangement rule, when the driving part is rotated, the driving part causes relative displacement in the axial direction with respect to each driven part, and there is no relative displacement in the axial direction between the two driven parts. The arrangement rule is that the ratio of the pitch circle diameters between the driven parts is the same as the ratio of the number of helical lines. The number of helical lines of the nut is not equal to the sum of the number of helical lines of the main thread and the number of helical lines of the two rollers.

[0016] As a result, in the planetary roller screw of the present invention, the helical directions of the nut / female thread and the roller / second male thread are the same, and the helical directions of the main thread / first male thread are opposite. Furthermore, when combined with the above-mentioned arrangement rules (the ratio of the pitch circle diameters between the passive parts is the same as the ratio of the number of helical lines, and the number of helical lines of the nut is not equal to the sum of the number of helical lines of the main thread and the number of helical lines of the two rollers), when rotation is performed with a specific driving part, no relative displacement occurs in the axial direction between the two passive parts, and the passive parts can be subjected to stable and smooth axial displacement in the axial direction relative to the driving part. Furthermore, by increasing the reduction ratio of the corresponding displacement amount, more precise displacement control can be achieved. In particular, due to the motion relationship between the driving part and the passive part in the planetary roller screw of the present invention, the planetary roller screw of the present invention can replace a hydraulic cylinder and can be applied to various machine tools, brake devices, robots, and other situations requiring precise linear motion control.

[0017] Furthermore, in the above arrangement rule, the nut is the driving part, the ratio of the pitch circle diameter of the main screw to the pitch circle diameter of the roller is the same as the ratio of the number of helical wires of the main screw to the number of helical wires of the roller, and when the driving part is rotated, the planetary unit is subjected to relative displacement with respect to the nut in the axial direction, while no relative displacement occurs between the main screw and the planetary unit in the axial direction. In this way, by using the nut as the driving part and the main screw or the planetary unit as the output in this arrangement, it is possible to achieve control by the expected precise motion and to increase structural strength.

[0018] Furthermore, in the above arrangement rules, the main screw is the driving unit, the ratio of the pitch circle diameter of the nut to the pitch circle diameter of the roller is the same as the ratio of the number of helical wires of the nut to the number of helical wires of the roller, and when the driving unit is rotated, the planetary unit is subjected to relative displacement in the axial direction with respect to the main screw, while no relative displacement occurs in the axial direction between the nut and the planetary unit. In this way, by using the main screw as the driving unit and the nut or the planetary unit as the output in this arrangement, it is possible to achieve control by the expected precise motion and to increase structural strength.

[0019] 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

[0020] 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.

[0021] Furthermore, each of the rollers has protrusions at both ends in the axial direction, and the planetary unit also has an annular frame that is installed between the main screw and the nut, the annular frame has two annular bodies arranged relative to each other in the axial direction, and the two annular bodies each have a plurality of recesses that are opposite to each other in the axial direction, and the recesses are used to fit the protrusions of each roller into the recesses that are locally corresponding to each other. In this way, the arrangement of the annular frame 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.

[0022] Furthermore, an elastic member is installed on each of the protruding portions of each roller, and each elastic member is in contact with the annular frame portion 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.

[0023] Furthermore, one of the tooth surfaces in the first male thread of the main screw, the female thread of the nut, and the second male thread of each roller is arc-shaped. In this way, the contact area between the second male thread of the roller and the first male thread and the female thread can be reduced, thereby reducing the corresponding frictional force, decreasing noise generation, and improving the smoothness of rotation.

[0024] Furthermore, the first male thread of the main screw has at least one main screw tooth, and the second male thread of each roller of the planetary unit has at least one roller tooth, and when screw rotation occurs between the first male thread and the second male thread, meshing rotation occurs between the at least one main screw tooth and the at least one roller tooth. In this way, when the planetary unit rotates, it is possible to ensure that each roller rotates in a simple rotational state, eliminate situations in which unexpected frictional forces are generated by sliding, and further improve the smoothness of rotation of the planetary roller screw.

[0025] Furthermore, the female thread of the nut has at least one nut tooth, and the second 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 second male thread, meshing rotation occurs between the at least one nut tooth and the at least one roller tooth. In this way, when the planetary unit rotates, it is possible to ensure that each roller rotates in a simple rotational state, eliminate situations in which unexpected frictional forces are generated by sliding, and further improve the smoothness of rotation of the planetary roller screw. [Brief explanation of the drawing]

[0026] [Figure 1] This is an exploded perspective view of the first embodiment of the planetary roller screw of the present invention. [Figure 2] Figure 1 is a cross-sectional view of the assembled state. [Figure 3] This is an enlarged view of the partial structure of area A in Figure 2. [Figure 4] This is a schematic diagram of the motion relationship when the planetary roller screw of the present invention uses a nut as the driving element. [Figure 5] This is a schematic diagram of the motion relationship when the planetary roller screw of the present invention uses a main screw as the driving element. [Figure 6] This is a schematic diagram of the interlocking screw teeth of the main screw and the roller. [Figure 7]This is a schematic diagram of the meshing screw teeth and spur gears of a 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]

[0027] 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.

[0028] 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, the planetary roller screw can further have a specific mode of motion based on the arrangement rules disclosed in the present invention. In particular, based on the arrangement rules, the planetary roller screw can have a first arrangement or a second arrangement, each having a different mode of motion. Details of the above arrangement rules are described below.

[0029] The outer circumference of the main screw 1 has a first male thread 11 extending along the axial direction, and the helical direction of the first 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, preferably the first 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 throughout the text of the present invention.

[0030] 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 first 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 first 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 first external thread 11 is aligned with the internal thread 21 in the radial direction.

[0031] 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 second male thread 311, and the helical direction of the second male thread 311 may be either right-handed or left-handed. In particular, the helical direction of the second male thread 311 and the helical direction of the female thread 21 of the nut 2 are the same, that is, the helical direction of the second male thread 311 and the helical direction of the first male thread 11 of the main thread 1 are opposite. At least a portion of each roller 31 is located inside the through hole 20 of the nut 2, and the second male thread 311 of each roller 31 is screwed into the first male thread 11 and the female thread 21, respectively. Preferably, each roller 31 is uniformly distributed around the outer circumference of the main thread 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 thread 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.

[0032] 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

[0033] 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 / first 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.

[0034] 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.

[0035] More specifically, as shown in Figure 3, the thread pitch P1 of the first male thread 11, the thread pitch P2 of the female thread 21, and the thread pitch P3 of the second male thread 311 are all the same.

[0036] Preferably, the tooth surface (Flank) 311F of the second male thread 311 is arc-shaped, which reduces the contact area between the roller 31 and the first male thread 11 and the female thread 21 of the second male thread 311, thereby reducing the frictional force between the second male thread 311 and the first male thread 11 and the female thread 21, 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 first male thread 11, the tooth surface 21F of the female thread 21, and the tooth surface 311F of the second male thread 311 arc-shaped, but the present invention is not limited thereto.

[0037] 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. Selectively, 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 in order to allow each roller 31 to be easily installed between the main screw 1 and the nut 2. Alternatively, in another example (not shown), without changing the arrangement of the axial height positions of each housing 320, 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.

[0038] According to the arrangement shown in Figures 1 to 3 above, the present invention discloses one arrangement rule, based on the condition that the helical direction of the first male thread 11 of the main screw 1 and the helical direction of the female thread 21 of the nut 2 are in opposite directions, and the helical direction of the female thread 21 of the nut 2 is the same as the helical direction of the second male thread 311 of the roller 31, one of the main screw 1 or the nut 2 is designated as the driving part, and the other two parts of the main screw 1, the nut 2 and the planetary unit 3 that are not the driving part are designated as passive parts. In the arrangement rule, the ratio of the pitch circle diameters between the passive parts is the same as the ratio of the number of helical lines, and the number of helical lines of the nut 2 is not equal to the sum of the number of helical lines of the main screw 1 and the number of helical lines of the two rollers 31. Preferably, the number of helical wires of the nut 2 is equal to the number obtained by adding the number of helical wires of the two rollers 31 to the number of helical wires of the main screw 1, and then adding or subtracting 1, or the number of helical wires of the main screw 1 is equal to the number obtained by subtracting the number of helical wires of the two rollers 31 from the number of helical wires of the nut 2, and then adding or subtracting 1. In this way, according to the arrangement rules described above, when the driving part is rotated, the driving part causes a relative displacement in the axial direction with respect to each of the passive parts, and does not cause a relative displacement in the axial direction between the two passive parts.

[0039] More specifically, Figure 4 shows an example of a first arrangement based on the arrangement rules described above, where the nut 2 is the driving part, the ratio of the pitch circle diameter of the main screw 1 to the pitch circle diameter of the roller 31 is the same as the ratio of the number of helical wires of the main screw 1 to the number of helical wires of the roller 31, and the number of helical wires of the nut 2 is not equal to the sum of the number of helical wires of the main screw 1 and the number of helical wires of the two rollers 31 (or the number of helical wires of the main screw 1 is not equal to the number of helical wires of the nut 2 minus the number of helical wires of the two rollers 31). Thus, the ratio of the pitch circle diameter of the nut 2 to the pitch circle diameter of the roller 31 is different from the ratio of the number of helical wires of the nut 2 to the number of helical wires of the roller 31. To clearly show the arrangement rules, T1 and D1 represent the number of helical wires and pitch circle diameter of the main screw 1, respectively; T2 and D2 represent the number of helical wires and pitch circle diameter of the nut 2, respectively; and T3 and D3 represent the number of helical wires and pitch circle diameter of the roller 31, respectively. The first arrangement in the above arrangement rules can be expressed as D1 / D3=T1 / T3 and T2≠T1+2T3 (T1≠T2-2T3), so D2 / D3≠T2 / T3. Preferably, the number of helical wires of the nut 2 is equal to the number obtained by adding the number of helical wires of the main screw 1 to the number of helical wires of the two rollers 31, and then adding or subtracting 1, that is, T2=T1+2T3±1. Preferably, the number of helical threads of the main screw 1 is equal to the number obtained by dividing the pitch circle diameter of the main screw 1 by the pitch circle diameter of the roller 31, that is, it can be expressed as T1 = D1 / D3.

[0040] More specifically, in the concrete example of the first arrangement, the screw pitch of the main screw 1, the nut 2, and the roller 31 is all 1.5 mm. The main screw 1 has a pitch circle diameter of 18 mm and 3 helical threads. The roller 31 has a pitch circle diameter of 6 mm and 1 helical thread. The nut 2 has a pitch circle diameter of 30 mm and 6 helical threads. When the nut 2 rotates once, the main screw 1 experiences a relative displacement of approximately 0.8 mm relative to the nut 2. In other words, in this case, the lead of the nut 2 in one rotation is 9 mm when its screw pitch of 1.5 mm is multiplied by the number of helical threads (6). Dividing this by the displacement of 0.8 mm output by the main screw 1 or the planetary unit 3, it can be seen that the reduction ratio of the corresponding displacement is approximately 11.25 times.

[0041] More specifically, Figure 5 shows an example of a second arrangement based on the arrangement rules described above, where the main screw 11 is the driving part, the ratio of the pitch circle diameter of the nut 2 to the pitch circle diameter of the roller 31 is the same as the ratio of the number of helical wires of the nut 2 to the number of helical wires of the roller 31, and the number of helical wires of the nut 2 is not equal to the sum of the number of helical wires of the main screw 1 and the number of helical wires of the two rollers 31. Thus, the ratio of the pitch circle diameter of the main screw 1 to the pitch circle diameter of the roller 31 is different from the ratio of the number of helical wires of the main screw 1 to the number of helical wires of the roller 31. In other words, the second arrangement in the arrangement rules described above can be expressed as D2 / D3=T2 / T3 and T2≠T1+2T3, so D1 / D3≠T1 / T3. Preferably, the number of helical wires of the main screw 1 is equal to the number obtained by subtracting the number of helical wires of the two rollers 31 from the number of helical wires of the nut 2, and then adding or subtracting 1, that is, it can be expressed as T1 = T2 - 2T3 ± 1.

[0042] More specifically, in the second configuration example, the screw pitches of the main screw 1, the nut 2, and the roller 31 are all 4 mm. The main screw 1 has a pitch circle diameter of 30 mm and 4 helical threads. The roller 31 has a pitch circle diameter of 10 mm and 1 helical thread. The nut 2 has a pitch circle diameter of 50 mm and 5 helical threads. When the main screw 1 rotates once, the nut 2 experiences a relative displacement of approximately 2 mm relative to the main screw 1. In other words, in this case, the lead of the main screw 1 in one rotation is 16 mm when its screw pitch of 4 mm is multiplied by the number of helical threads (4). Dividing this by the displacement of 2 mm output by the nut 2 or the planetary unit 3, it can be seen that the reduction ratio of the corresponding displacement is approximately 8 times.

[0043] In another specific example of the second arrangement described above, it is preferable that the number of helical threads of the main screw 1 is equal to the number obtained by dividing the pitch circle diameter of the main screw 1 by the pitch circle diameter of the roller 31. That is, it can be expressed as T1 = D1 / D3. The screw pitches of the main screw 1, the nut 2, and the roller 31 are the same, the main screw 1 has a pitch circle diameter of 20 mm and 1 helical thread, the roller 31 has a pitch circle diameter of 20 mm and 2 helical threads, and the nut 2 has a pitch circle diameter of 60 mm and 6 helices. In this specific example, D2 / D3 = T2 / T3, T1 = D1 / D3, and T1 = T2 - 2T3 - 1 (D1 / D3 ≠ T1 / T3) are satisfied.

[0044] 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 second male thread 311 is the same, while the helical direction of the first male thread 11 is in the opposite direction. In other words, it can be considered as "nut 2 - roller 31 - main thread 1" from outside to inside, and the corresponding helical directions can be indicated as "right - right - left" or "left - left - right".

[0045] It should be noted that, according to the arrangement rules in Figures 4 and 5 for the planetary roller screw of the present invention, the planetary roller screw of the present invention, based on the same standard of the pitch circle diameters of the main screw 1, the nut 2, and the roller 31 being 3:5:1, has a displacement reduction ratio of approximately 11.25 times in the first arrangement where the nut 2 is the driving part, and a displacement reduction ratio of approximately 8 times in the second arrangement where the main screw 1 is the driving part. However, if similar arrangement conditions are applied to conventional technology where all helical directions are the same, the ratio of the pitch circle diameters of the main screw 91, the nut 92, and the roller 31 is also set to 3:5:1, the screw pitch is 4 mm, the main screw 91 has a pitch circle diameter of 30 mm and 5 helical wires, the roller 93 has a pitch circle diameter of 10 mm and 1 helical wire, and the nut 92 has a pitch circle diameter of 50 mm and 5 helical wires. When the main screw 91 is used as the driving part and rotated once on the main screw, the relative displacement of the nut 92 with respect to the main screw 91 is approximately 20 mm. In other words, in this case, the lead of the main screw 91 in one rotation is 20 mm when its screw pitch of 4 mm is multiplied by the number of helical wires (5), and when divided by the displacement of 20 mm output by the nut 92, it can be seen that the reduction ratio of the corresponding displacement is approximately 1. That is, based on similar arrangement conditions, the planetary roller screw disclosed in the present invention can have a better reduction ratio of displacement. It should be noted that the specific proportional relationships of the pitch circle diameters between each component, the screw pitch of each component, the pitch circle diameter, and / or the number of helical wires described in this invention are merely examples to more clearly illustrate the content of this invention and do not limit it.

[0046] Therefore, by operating under the same or approximate screw pitch arrangement conditions as the conventional technology, based on the helical arrangement disclosed in the present invention and the arrangement rules described above, the relative displacement between the main screw 1 and the nut 2 can be reduced by the present invention, thereby achieving even more precise motion control. Furthermore, since the corresponding screw pitch arrangement conditions of the main screw 1, the nut 2, and the roller 31 are maintained in their original state (not more tightly adjusted), the main screw 1, the nut 2, and the roller 31 can maintain similar load-bearing capacity without unnecessarily increasing the corresponding processing costs. In other words, compared to the conventional technology, when seeking control with similar displacement accuracy, that is, when the driving part completes one rotation and the passive part has the same displacement, 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] 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 first male screw 11 and the second 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.

[0048] 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 first male screw 11. However, in other embodiments (not shown), the main screw teeth 1G may be arranged in a single row or in multiple rows in one or more local areas of the first 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 second 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 second male screw 311, or in a single row or in multiple rows in one or more local areas of the second male screw 311 or the roller 31. In particular, the main screw teeth portion 1G consists of multiple concave structures or multiple protruding structures formed on the first male thread 11, and the roller teeth portion 31G is used to mesh with the main screw teeth portion 1G and consists of multiple concave structures or multiple protruding structures formed on the second male thread 311 of each roller 31.

[0049] 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 first 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 second 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 main screw teeth 1G and roller teeth 31G with spur gear structures shown in Figure 7 are arranged 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 arranged 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 first 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 first male screw 11 of the main screw 1. For example, when arranging the roller teeth 31G of a spur gear structure, the second 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 second male screw 311 of the roller 31.

[0050] 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 second 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.

[0051] 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 second male 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 second male thread 311, or in a single row or in multiple rows, respectively, in one or more local areas of the second male thread 311 or the roller 31.

[0052] 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 second 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 are located 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 located 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 second 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 second male thread 311 of the roller 31.

[0053] 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 first male screw 11, female screw 21, and second male screw 311 must be considered, and it is preferable that the smallest of these pitch circle diameters divides the others evenly.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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 passive 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 relationship of motion 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.

[0058] In summary, the planetary roller screw of the present invention, by having the helical directions of the nut / female thread and the roller / second male thread in the same direction, and the helical directions of the main thread / first male thread in opposite directions, and further combining this with the above-mentioned arrangement rules (the ratio of the pitch circle diameters between the passive parts is the same as the ratio of the number of helical lines, and the number of helical lines of the nut is not equal to the sum of the number of helical lines of the main thread and the number of helical lines of the two rollers), allows for rotation with a specific driving part without causing relative displacement in the axial direction between the two passive parts, and allows for stable and smooth axial displacement of the passive parts relative to the driving part. Furthermore, by increasing the reduction ratio of the corresponding displacement amount, more precise motion control can be achieved. In particular, due to the motion relationship between the driving part and the passive part in the planetary roller screw of the present invention, the planetary roller screw of the present invention can replace hydraulic cylinders and be applied in various situations where precise linear motion control is required, such as in various machine tools, brake devices, and robots.

[0059] Furthermore, it should be noted that the planetary roller screw of the present invention, in accordance with the arrangement rules described above, in particular, has the effect of being able to rotate smoothly even when the arrangement of the main screw teeth, nut teeth, and roller teeth is omitted, that is, when any of the main screw teeth, nut teeth, and roller teeth are not required, by arranging them in such a specific relationship that the pitch circle diameter and the number of helical lines of the main screw, nut, and roller are in a particular relationship.

[0060] 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]

[0061] 1 Main screw 11 First 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 Second male thread 311F Tooth surface 312 Protrusion 32 Ring frame section 320 Storage Unit 321 Ring-shaped body 321C recess C center axis E Elastic member G Gap H Height L Length P1 thread pitch P2 screw pitch P3 thread pitch 9 Planetary roller screw 91 Main screw 911 First male thread 92 Nuts 921 Female thread 93 Laura 931 Second male thread

Claims

1. Includes main screw, nut and planetary unit, The main screw has a first male thread formed on its outer circumference that extends axially, 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 first 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 second male thread on its outer circumference, each of which is locally located at least within the through hole of the nut, and the second male thread of each roller is screwed into the first male thread and the female thread, respectively. The screw pitch of the first male thread, the screw pitch of the female thread, and the screw pitch of the second male thread are the same, the helical direction of the first male thread and the helical direction of the female thread are opposite, and the helical direction of the female thread and the helical direction of the second male thread are the same. One of the main screw or the nut is defined as the driving part, and the other two parts of the main screw, the nut, and the planetary unit that are not the driving part are defined as passive parts, and the planetary roller screw is arranged such that when the driving part is rotated, the driving part causes a relative displacement in the axial direction with respect to each passive part, and no relative displacement in the axial direction occurs between the two passive parts. The arrangement rule is characterized in that the ratio of the pitch circle diameters between the passive parts is the same as the ratio of the number of helical wires, and the number of helical wires of the nut is not equal to the sum of the number of helical wires of the main screw and the number of helical wires of the two rollers.

2. The planetary roller screw according to claim 1, characterized in that, in the arrangement rule, the nut is the driving part, the ratio of the pitch circle diameter of the main screw to the pitch circle diameter of the roller is the same as the ratio of the number of helical wires of the main screw to the number of helical wires of the roller, and when the driving part is rotated, the planetary unit is subjected to relative displacement with respect to the nut in the axial direction, and no relative displacement occurs between the main screw and the planetary unit in the axial direction.

3. The planetary roller screw according to claim 1, characterized in that, in the arrangement rule, the main screw is the driving part, the ratio of the pitch circle diameter of the nut to the pitch circle diameter of the roller is the same as the ratio of the number of helical wires of the nut to the number of helical wires of the roller, and when the driving part is rotated, the planetary unit is subjected to relative displacement with respect to the main screw in the axial direction, and no relative displacement occurs between the nut and the planetary unit in the axial direction.

4. 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 3.

5. The planetary roller screw according to claim 4, 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.

6. The planetary roller screw according to any one of claims 1 to 3, 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.

7. The planetary roller screw according to claim 6, 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.

8. The planetary roller screw according to any one of claims 1 to 3, characterized in that the tooth surface of any one of the first male thread of the main screw, the female thread of the nut, and the second male thread of each roller is arc-shaped.

9. The planetary roller screw according to any one of claims 1 to 3, wherein the first male thread of the main screw further has at least one main screw tooth, and the second male thread of each roller of the planetary unit has at least one roller tooth, and when screw rotation occurs between the first male thread and the second male thread, meshing rotation occurs between the at least one main screw tooth and the at least one roller tooth.

10. The planetary roller screw according to any one of claims 1 to 3, characterized in that the female thread of the nut has at least one nut tooth, the second male thread of each of the rollers of the planetary unit has at least one roller tooth, and when screw rotation occurs between the female thread and the second male thread, meshing rotation occurs between the at least one nut tooth and the at least one roller tooth.

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