TWI673446B - Planetary screw and machine tool including the same - Google Patents

Abstract

A planetary screw and a machine tool with the same are used to solve the problems of complex structure and rotation noise of the conventional planetary screw. The system includes: a main screw with an external thread and a connecting portion; a nut with a hole penetrating through two end surfaces of the nut; the inner wall surface forming the hole has an internal thread; and a planetary group with a supporting structure A plurality of rollers are supported for positioning and rotation on the supporting structure, the plurality of rollers are identical to each other and have external threads, and the external threads of each of the plurality of rollers are engaged with the external threads of the main screw and the internal threads of the nut. The planetary screw system can be used in a machine tool.

Description

Planetary screw and machine tool with the planetary screw

The invention relates to a linear translation mechanism and a machine tool having the linear translation mechanism, in particular to a planetary screw for converting a rotary motion into a linear translational motion, or a linear translational motion into a rotary motion, and a planetary screw having the planetary screw. Machine tool.

Please refer to FIGS. 1 and 2, which is a conventional planetary screw 9. The planetary screw 9 is provided with a plurality of rollers 93 between a main screw 91 and a nut 92. The main screw 91 has an external thread 911. The nut 92 has an internal thread 921 and a non-threaded portion 922 on both sides of the internal thread 921 section. The non-threaded portion 922 accommodates a collar 94 having an inner ring tooth 941 and a fixing plate 95 therein. The rollers 93 are identical to each other and have external threads 931 and external teeth 932, and two ends of the rollers 93 are respectively sleeved on the two fixing plates 95, and the rollers 93 are distributed at equal angular intervals in the Around the main screw 91 and coaxial with the main screw 91, the external thread 931 of the plurality of rollers 93 and the internal thread 921 of the nut 92 and the external thread 911 of the main screw 91 mesh with each other. The tooth portion 932 is engaged with the inner ring tooth 941 of the collar 94, so that the nut 92 can be moved axially relative to the main screw 91, or the main screw 91 can be moved axially relative to the nut 92.

In addition, in order to keep the planetary stud 9 rotating smoothly, an oil seal 951 is additionally provided between the two fixing plates 95 and the collar 94, and lubricating oil is filled in the nut 92 and between the two fixing plates 95, and the The main screw 91 is further screwed with two end caps 96, which close the two end edges of the nut 92 to prevent the lubricant from being lost.

In the above-mentioned conventional planetary stud 9, in order to ensure that the plurality of rollers 93 can stably rotate around the main screw 91 and the nut 92, the outer teeth 932 are additionally processed on the plurality of rollers 93, and The two non-threaded portions 922 are machined in the nut 92 and the collar 94 is housed, and the inner ring teeth 941 are machined in the collar 94. Thus, the structure of the conventional planetary screw is complicated, and the processing cost is increased. .

In addition, the lubricating oil will still gradually drain through the external threads 911 and 931 where the main screw 91 and the rollers 93 are screwed together, resulting in noise when the planetary screw rotates, and it is necessary to disassemble the two frequently. After the end cap 96, the two fixing plates 95, the collar 94, and the rollers 93, the lubricant is filled in the nut 92 and between the two fixing plates 95, so that the filling of the lubricant is changed. Trouble and difficulty.

In view of this, the conventional planetary screw does still need to be improved.

Directionality or its approximate terms as described throughout the present invention, such as "front", "rear", "left", "right", "up (top)", "down (bottom)", "inside", "outside" , "Side", etc., are mainly referred to the directions of the attached drawings, and the directivity or its approximate terms are only used to help explain and understand the embodiments of the present invention, not to limit the present invention.

The approximate terms such as "combination", "combination" or "assembly" in the full text of the present invention mainly include types that can still be separated without damaging the components after connection, or that the components cannot be separated after connection; for example, with threaded component phases Connection methods such as screwing or welding are those who have ordinary knowledge in the art and can choose according to the material or assembly requirements of the components to be connected.

The machine tool according to the present invention is a variety of power transmission and output machines that can be used to convert rotary motion into linear translation motion, or convert linear translation motion into rotary motion. Examples include, but are not limited to, plastic molding machines, punches, linear actuators, 3D printers, and the like.

In order to solve the above problems, an object of the present invention is to provide a planetary screw, which can simplify the structure and further reduce the processing cost.

A secondary object of the present invention is to provide a planetary screw, which has a simple structure and can be easily filled with lubricating oil, and can further reduce noise when the planetary screw rotates.

Another object of the present invention is to provide a machine tool with the planetary screw, which can be easily repaired and filled with lubricating oil, and can further reduce the failure rate of the machine and the noise when the planetary screw rotates.

The planetary screw of the present invention comprises: a main screw having an external thread and a connecting portion; a nut having a hole penetrating through two end surfaces of the nut; an inner wall surface forming the hole has an internal thread; the nut has a through hole Two through holes on the inner and outer wall surfaces, each of which is connected to an oil guide pipe; and a planetary group having a supporting structure to support a plurality of rollers for positioning and rotation on the supporting structure, the plurality of rollers being the same as each other and having External threads, the external threads of each of the plurality of rollers mesh with the external threads of the main screw and the internal threads of the nut.

The planetary screw of the present invention further comprises: a main screw having an external thread and a connecting portion; a nut having a hole penetrating through two end surfaces of the nut; an inner wall surface forming the hole has an internal thread; and a planet A group has a supporting structure for supporting a plurality of rollers for positioning and rotation on the supporting structure. The plurality of rollers are identical to each other and have external threads. The external threads of each of the plurality of rollers and the external threads of the main screw and the internal of the nut. The support structure is composed of two fixing plates and a plurality of fixing posts. The central part of the two fixing plates each has a perforation and several assembly holes surrounding the perforation. The assembly holes are located in the The center of the perforation is a circle with the same radius on the center of the circle, and two ends of the plurality of fixing posts are respectively connected to the assembly hole.

According to this, the planetary screw of the present invention is mainly in contact with the main screw and the nut through the support structure, and only by the external threads of the rollers and the external thread of the main screw and the nut. The internal thread meshes so that the rollers can rotate and rotate relative to the main screw and nut. The revolution, as a whole, has a relatively simple structure and can reduce friction. In this way, the processing cost of the planetary screw can be greatly reduced, and the production and assembly efficiency can be improved. And because the support structure is not in direct contact with the main screw and the nut, the noise generated when the planetary screw rotates can be reduced, the lubricating oil can be filled into the nut cyclically, and the support structure can be stably The effect of supporting the plurality of rollers to perform positioning and rotation is supported.

Wherein, the inner wall surface is a stepped hole, the inner wall of the middle section has a first inner diameter, the inner wall surface at the two ends of the nut has a second inner diameter, and the second inner diameter portion is a close-fitting portion. The inner diameter dimension of the close portion is larger than the inner diameter dimension of the first inner diameter, and the inner thread is located at the first inner diameter portion. In this way, it is ensured that the external threads of the plurality of rollers will only engage with the internal threads of the nut, so as to avoid the effect that the external threads of the plurality of rollers collide with other internal wall surfaces of the nut.

Wherein, two ends of the plurality of fixing posts each have a joint portion protruding from one of the two fixing plates, the joint portion has external threads, and each of the joint portions is provided with a joint member for screwing and fixing. In this way, the plurality of fixed columns can be easily disassembled and combined, so that the support structure and the plurality of rollers can be easily repaired and replaced.

Wherein, the plurality of fixing posts each have external threads and are identical to each other, each of the external threads can be respectively engaged with the external thread of the main screw and the internal thread of the nut, and each of the coupling members and the two fixing plates are each There is a gap, each of which is slightly larger than the meshing gap of the external thread of each of the fixing posts with the external thread of the main screw and the internal thread of the nut. In this way, the plurality of fixing posts can be rotated and revolved relative to the main screw and the nut.

Wherein, the coupling member is sunk in the assembly hole. In this way, the coupling member has the effect that it does not protrude from the surface of the fixing plate.

Wherein, the coupling member protrudes from the outer surfaces of the two fixing plates and does not contact the nut. In this way, the system can prevent the coupling member from colliding with the nut, and the fixing column system can be easily removed.

Wherein, two ends of the plurality of rollers each have an assembling part, and each of the assembling parts can pass through the assembling holes of the two fixing plates to move and rotate. In this way, the system can ensure that the rollers are smoothly rotated between the two fixed plates.

Among them, the number of planetary rollers between any two adjacent fixed columns is the same. In this way, the plurality of fixed columns can uniformly withstand the frictional forces of the rollers and the main screw and the nut during the revolution, and has the effect of achieving a good balance of force.

Wherein, the close ends of the two ends of the nut each have a closure member, and the closure member is detachably coupled to the nut. In this way, the closure can seal the lubricating oil in the hole of the nut, to prevent the lubricating oil from leaking out, to improve the cleanliness of the working environment, and to prevent external dust or foreign objects from falling into the screwing space to avoid affecting the The effect of smooth rotation of the nut and the main screw.

The closure member is made of an elastic material. In this way, the closure member has a better sealing effect and can prevent the leakage of lubricating oil.

Wherein, the closing member and the main screw are screwed together by threads, and the closing member and the main screw have a different pitch or screw shape. In this way, the sealing member can ensure that the lubricating oil can be enclosed in the hole of the nut, and the effect of preventing the lubricating oil from leaking out from the screwing part of the sealing member and the main screw can be avoided.

In addition, the planetary screw system of the present invention can be used in a machine tool. The system can be used to convert a rotary motion into a linear translational motion, or convert a linear translational motion into a rotary motion. The planetary screw system can be easily repaired and filled. Lubricants and other effects.

〔this invention〕

1‧‧‧ main screw

11‧‧‧external thread

12‧‧‧ Connection Department

2‧‧‧ Nut

2a‧‧‧first inner diameter

2b‧‧‧Second inner diameter

2c‧‧‧Third inner diameter

21‧‧‧ Internal thread

22‧‧‧ Adhering Department

23‧‧‧Breakthrough Department

24‧‧‧through hole

25‧‧‧ plug

26‧‧‧Positioning element

3‧‧‧ planetary group

31‧‧‧Fixed plate

311‧‧‧perforation

312‧‧‧Assembly hole

32、32’‧‧‧Fixed posts

321、321’‧‧‧Combination

322, 322’‧‧‧ combination

323’‧‧‧External thread

33‧‧‧ roller

331‧‧‧Assembly Department

34‧‧‧Missing parts

4‧‧‧ closure

41‧‧‧ through hole

42‧‧‧internal thread

G‧‧‧ Clearance

〔Usually〕

9‧‧‧ planetary screw

91‧‧‧main screw

911‧‧‧external thread

92‧‧‧ Nut

921‧‧‧ Internal thread

922‧‧‧unthreaded

921‧‧‧ Internal thread

922‧‧‧unthreaded

93‧‧‧Roller

931‧‧‧external thread

932‧‧‧Outer teeth

94‧‧‧ Collar

95‧‧‧Fixing plate

951‧‧‧oil seal

96‧‧‧ end cap

[Fig. 1] A structure diagram of a conventional planetary screw.

[FIG. 2] An exploded perspective view of the first preferred embodiment of the present invention.

[Figure 3] An exploded perspective view of the planetary group of the first preferred embodiment of the present invention.

[Fig. 4] An assembled sectional view of the first preferred embodiment of the present invention.

[Fig. 5] An enlarged view of the partial structure A shown in Fig. 4.

[Fig. 6] Structure drawing of main screw and nut in part B as shown in Fig. 4.

[FIG. 7] An assembled sectional view of a second preferred embodiment of the present invention.

In order to make the above and other objects, features, and advantages of the present invention more comprehensible, the following describes the preferred embodiments of the present invention in detail with the accompanying drawings as follows: Please refer to FIG. 2, It is a first embodiment of the planetary screw of the present invention, and includes a main screw 1, a nut 2, and a planetary group 3. The planetary group 3 is located in the nut 2 and surrounds the main screw 1. The main screw 1 may be linearly moved relative to the nut 2 and the planetary group 3 in the axial direction, or the nut 2 and the planetary group 3 may be linearly moved relative to the main screw 1 in the axial direction.

The main screw 1 has an external thread 11. The external thread 11 may be located at one end of the main screw 1. The main screw 1 further has a connecting portion 12. The connecting portion 12 may be located at the other end of the main screw 1. The part 12 can be connected with a power device (not shown), so that the main screw 1 can be driven to rotate.

The nut 2 has a hole penetrating the two end surfaces, and the inner wall surface of the nut 2 forming the hole may be a hole with a single diameter, or the inner wall surface may be a stepped hole without the same diameter. In this embodiment, The inner wall surface is a stepped hole. The inner wall of the middle section has a first inner diameter 2a. The inner wall surface formed on the two ends of the nut 2 has a second inner diameter 2b and an inner diameter of the second inner diameter 2b. The size is larger than the inside diameter of the first inside diameter 2a. Preferably, there is a third inside diameter 2c between the two second inside diameter 2b and the first inside diameter 2a. The inner diameter dimension is between the first inner diameter 2a and the inner diameter dimension of the second inner diameter 2b. The inner wall surface of the nut 2 forming the first inner diameter 2a has an internal thread 21, and the inner wall surface of the nut 2 forming the second inner diameter 2b may be an abutting portion 22, and forming the third inner diameter The inner wall surface of the nut 2 in 2c may be a hollow portion 23. The nut 2 preferably has at least one through hole 24 penetrating the inner and outer wall surfaces. Each of the at least one through hole 24 can be closed by a plug member 25 so that the lubricating oil can be filled in the nut 2 with the at least one through hole 24. Inside. In addition, when the nut 2 is fixed and does not rotate, the through hole 24 can be two, and each of the two through holes 24 can be connected to an oil guide pipe (not shown), so that the lubricating oil can be passed through the two through The holes 24 form a loop, which will have better lubrication effect.

Please refer to Figures 2, 3, and 4. The planetary group 3 has a supporting structure. The supporting structure can support the positioning and rotation of a plurality of rollers 33. In this embodiment, the supporting structure is composed of two fixed plates 31. A plurality of fixing posts 32 are provided. The central portions of the two fixing plates 31 each have a perforation 311. The main screw 1 can pass through without touching the two perforations 311. Each of the fixing plates 31 further has a plurality of assembling holes 312 surrounding the perforation 311, and the plurality of assembling holes 312 are arranged on a circle with the same radius around the perforation 311.

The plurality of fixing posts 32 are respectively connected to the two fixing plates 31 at two ends, so that the plurality of fixing posts 32 and the two fixing plates 31 can form a stable support structure together, and the plurality of fixing posts 32 surround the The outer periphery of the main screw 1 is not in contact with the main screw 1 and the nut 2. In this embodiment, two ends of each of the fixing posts 32 each have a joint portion 321 protruding from the two fixing plates 31, and each of the protruding joint portions 321 can be fixedly combined with a joint piece 322. In the embodiment, the coupling portion 321 may have an external thread, and the coupling member 322 may be a nut; the coupling member 322 may be sunk in the assembly hole 312, or the coupling member 322 may protrude from the two fixing plates 31. On the outer surface, the two fixing plates 31 and the protruding coupling member 322 may correspond to the third inner diameter 2c portion of the nut 2, and the two fixing plates 31 and the coupling member 322 are not different from the third inner diameter. 2c contact.

Each of the two ends of the plurality of rollers 33 has an assembly portion 331, and the two assembly portions 331 Each of the plurality of rollers 33 is the same as each other and each has an external thread 332, and each of the external threads 332 can be externally threaded with the main screw 1 respectively. 11 and the internal thread 21 of the nut 2 mesh, so that in the case that the two fixing plates 31 and the plurality of fixing posts 32 of the supporting structure do not contact the main screw 1 and the nut 2, each of the rollers 33 is It can revolve and rotate with respect to the main screw 1 and the nut 2.

The external thread 332 of the roller 33 may be the same as the external thread 11 of the main screw 1 and the internal thread of the nut 2. In addition, the shape of the external thread 11 of the main screw 1 and the shape of the nut 2 The shape of the internal thread 21 is preferably the same, and the shape of the external thread 332 of the roller 33 is preferably different from the shape of the external thread 11 of the main screw 1 and the shape of the internal thread 21 of the nut 2, as shown in FIG. 5, The shape of the external thread 11 of the main screw 1 and the shape of the internal thread 21 of the nut 2 are formed into a mountain shape. The external thread 322 of the roller 33 forms an arc angle. In this way, the external thread of the roller 33 can be reduced. The contact area between 332 and the external thread 11 of the main screw 1 can reduce the friction between the two external threads 11, 332, and has the effects of reducing noise generation and improving smoothness of rotation. In contrast, in other embodiments, the shape of the external thread 11 of the main screw 1 and the shape of the internal thread 21 of the nut 2 can be selected to form a rounded angle, and the external thread 332 of the roller 33 is formed into a mountain shape. The form of the present invention is not limited.

The centers of the plurality of rollers 33 and the plurality of fixed columns 32 are preferably on the same radius circle, and are arranged around the outer circumference of the main screw 1 in a regular manner at an equiangular distribution, and the plurality of rollers 33 and The plurality of fixed posts 32 are preferably arranged at an integer ratio, so that any two adjacent fixed posts 32 have the same number of rollers 33. For example, in this embodiment, the total number of the rollers 33 and the fixed posts 32 is nine, and the ratio of the number of the rollers 33 to the fixed posts 32 is 2: 1. The plurality of fixing posts 32 can evenly bear the frictional force of the plurality of rollers 33 and the main screw 1 and the nut 2 in revolutions, so as to achieve a good balance of force.

Please refer to FIG. 2 and FIG. 4, the two opposite end surfaces of the nut 2 in the axial direction are each different. There is a closure member 4 which is detachably coupled to the close portion 22 of the nut 2. The closure member 4 is capable of sealing the lubricating oil in the hole of the nut 2 to avoid the lubricating oil. Leakage to improve the cleanliness of the working environment, and prevent external dust or foreign objects from falling into the screwing space of the nut 2, and avoid affecting the smoothness of the rotation of the nut 2 and the main screw 1. In this embodiment, a positioning element is used to penetrate the nut 2 to fix the closure member 4 so that the closure member 4 and the nut 2 can rotate synchronously. Preferably, the closure member 4 and the nut 2 There is preferably a leakage stopper 34 in order to avoid the leakage of lubricating oil from the joint between the closure member 4 and the nut 2. The closing member 4 has a penetrating hole 41 for the main screw 1 to penetrate and extend, so that the main screw 1 can penetrate axially through the inside of the nut 2. The penetrating hole 41 may have an internal thread 42. The main screw 1 is screwed with an external thread 11. Thereby, the closing member 4 and the nut 2 can be integrated with the main screw 1 for relative movement to be used in a machine tool, for example, in a plastic injection molding machine, the closing member 4 and the nut 2 can be formed into a single piece. Positioning rotation, the main screw 1 can make relative linear movement to eject the plastic from the nozzle; or, in other processing machinery, the main screw 1 can rotate in a positioning manner, so that the closure 4 and the nut 2 can For relative axial displacement workers.

Please refer to FIG. 6, the closure member 4 may also be made of elastic materials such as silicon rubber, rubber, so that the internal thread 42 of the closure member 4 can be attached to the external thread 11 of the main screw 1 to The leakage of lubricating oil is prevented as the main screw 1 rotates. Alternatively, the pitch D1 of the internal thread 42 of the closure 4 and the pitch D2 of the external thread 11 of the main screw 1 may be formed differently; or the spiral shape of the internal thread 42 of the closure 4 and the main screw 1 may be different. The external shape of the external thread 11 is different; by this, the internal thread 42 of the closure 4 and the external thread 11 of the main screw 1 can further form a closer fit, and the material of the closure 4 has The elasticity does not cause too much obstruction to the rotation of the main screw 1, and has the effect of improving the tightness of the closing member 4 and the main screw 1.

Please refer to FIG. 7, which is the second embodiment of the planetary screw of the present invention, and Compared with an embodiment, in this embodiment, the plurality of fixing posts 32 ′ each have an external thread 323 ′ and are the same as each other, and each of the external threads 323 ′ may be respectively the external thread 11 and the nut of the main screw 1. The internal threads 21 of 2 are engaged with each other; the plurality of fixing posts 32 ′ can extend through the two fixing plates 31 from the two ends, so that a joint portion 321 ′ of one of the plurality of fixing posts 32 ′ can protrude from the two fixings. Plate 31, and each of the two joints 321 'can be combined by a joint 322', the two joints 321 'can be external threads, each joint 322' can be a nut, each joint 322 'and There is a gap G between the two fixing plates 31, and the gap G is slightly larger than the meshing clearance between the external thread 323 'and the external thread 11 of the main screw 1 and the internal thread 21 of the nut 2. The two fixing posts 32 ′ and the two fixing plates 31 may form a stable supporting structure together, and the plurality of fixing posts 32 ′ may be moved in a slight axial direction relative to the two fixing plates 31. The coupling member 322 'can be sunk in the assembly hole 312, or the coupling member 322' can protrude from the outer surface of the two fixing plates 31, and the two fixing plates 31 and the protruding coupling member 322 'are not related to each other. The third inner diameter 2c of the nut 2 is in contact with each other.

With the above structure, when the planetary screw of the present invention is actuated, the main screw 1 can be driven to rotate, so that the plurality of rollers 33 engaged with the external thread 11 of the main screw 1 and the internal thread 21 of the nut 2 can be formed. Self-rotation and common revolution around the main screw 1, so that when the nut 2 rotates in position, the main screw 1 can make relative linear movement, and the forward and reverse rotation of the main screw 1 makes the The main screw 1 can make repeated linear movements; or when the main screw 1 rotates in a fixed position, the closure member 4 and the nut 2 can make relative axial displacements, and by the positive and negative directions of the main screw 1 By rotating, the closing member 4 and the nut 2 can be moved linearly repeatedly.

In summary, the planetary screw of the present invention is mainly in contact with the main screw and the nut through the support structure, and only by the external threads of the rollers and the external threads of the main screw and The internal thread of the nut is meshed, so that the rollers can rotate and revolve relative to the main screw and the nut. The overall structure is relatively simple and friction can be reduced. In this way, the planetary screw can be greatly reduced. Processing costs, and can improve production and assembly efficiency. And because of this support The structure is not in direct contact with the main screw and the nut, so that the noise and other effects caused by the planetary screw can be reduced. In addition, when the planetary screw of the present invention is used in a machine tool, it can also be easily maintained and easily filled with lubricating oil.

Although the present invention has been disclosed using the above-mentioned preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various changes and modifications to the above embodiments without departing from the spirit and scope of the present invention. The technical scope protected by the invention, so the scope of protection of the present invention shall be determined by the scope of the appended patent application.

Claims (13)

A planetary screw includes: a main screw having an external thread and a connecting portion; a nut having a hole penetrating through two end surfaces of the nut; an inner wall surface forming the hole has an internal thread; the nut has a through hole 2. Two through holes on the outer wall surface, each of the two through holes being connected to an oil guide pipe; and a planetary group having a supporting structure to support the positioning and rotation of a plurality of rollers on the supporting structure, the plurality of rollers being identical to each other and having external threads , The external thread of each of the plurality of rollers meshes with the external thread of the main screw and the internal thread of the nut. A planetary screw includes: a main screw having an external thread and a connecting portion; a nut having a hole penetrating through two end surfaces of the nut; an inner wall surface forming the hole has an internal thread; and a planetary group having A supporting structure supports a plurality of rollers for positioning and rotation on the supporting structure. The plurality of rollers are identical to each other and have external threads. The external threads of each of the plurality of rollers are engaged with the external threads of the main screw and the internal threads of the nut. The supporting structure is composed of two fixing plates and a plurality of fixing posts. Each of the two fixing plates has a perforation at the center and a plurality of assembly holes surrounding the perforation. The assembly holes are located at the center of the perforation. On the circumference of the same radius of the center, two ends of the plurality of fixing posts are respectively connected to the assembly hole. The planetary screw according to item 1 or 2 of the scope of the patent application, wherein the inner wall surface is a stepped hole, the inner wall of the middle section has a first inner diameter, and the inner wall surface of the two ends of the nut has a second Inner diameter, the second inner diameter portion is a close-contact portion, the inner diameter size of the close-up portion is larger than the inner diameter size of the first inner diameter, and the inner thread is located at the first inner diameter portion. The planetary screw according to item 2 of the scope of patent application, wherein two ends of the plurality of fixing posts each have a joint portion protruding from one of the two fixing plates, the joint portion has external threads, and each of the joints The joint part is used for fixing a joint member by screwing. The planetary screw according to item 4 of the scope of patent application, wherein the plurality of fixing posts each have an external thread and are the same as each other, and each of the external threads can be engaged with the external thread of the main screw and the internal thread of the nut, respectively There is a gap between each of the coupling members and the two fixing plates, and each of the gaps is larger than the engagement gap between the external thread of each of the fixing posts, the external thread of the main screw, and the internal thread of the nut. The planetary screw according to item 4 of the scope of the patent application, wherein the coupling member is sunk in the assembly hole. The planetary screw according to item 4 of the scope of patent application, wherein the coupling member protrudes from the outer surface of the two fixing plates and does not contact the nut. According to the planetary screw described in item 2 of the scope of the patent application, each of the two ends of the plurality of rollers has an assembly portion, and each of the assembly portions can pass through the assembly holes of the two fixed plates for rotation. The planetary screw according to item 8 of the scope of patent application, wherein the number of planetary rollers between any two adjacent fixed columns is the same. The planetary screw according to item 3 of the scope of the patent application, wherein each of the close ends of the nut has a closure member, and the closure member is detachably coupled to the nut. The planetary screw according to item 10 of the patent application scope, wherein the closure member is made of an elastic material. The planetary screw according to item 11 of the scope of the patent application, wherein the closure member and the main screw are screwed together, and the closure member has a different pitch or screw shape from the outer screw of the main screw. A machine tool has a planetary screw as described in claims 1, 2, 4, 5, 6, 7, 8, 9, 11, or 12.