Planetary roller screw and electric cylinder

Abstract

The utility model relates to the technical field of screw nut mechanism, specifically relates to planet roller screw pair and electric cylinder. Planet roller screw pair includes nut, screw and roller, and the axial both sides of thread section on roller are equipped with limit section respectively, the diameter of limit section is less than the diameter of thread section, and the thread section of roller is all screwed with nut and screw, and the thread rotation direction of nut is opposite with the thread rotation direction of roller, the part of limit section of roller and corresponding limit section of nut is equipped with the ring groove around the axis, the inner diameter of the part of nut and is equipped with ring groove is less than the inner diameter of its part and is equipped with thread, and the part between the ring groove of roller and the adjacent two ring grooves of nut cooperates to restrict roller, makes the revolution and rotation movement of roller around screw, and this structure is simple to process, and the technology is easy to realize, and it is favorable for reducing production manufacturing cost.

Description

Technical Field

[0001] This utility model relates to the field of lead screw and nut mechanism technology, specifically to planetary roller lead screw pairs and electric cylinders. Background Technology

[0002] There are many ways to convert rotary motion into linear motion in mechanical transmission, such as threaded drives, ball screw drives, and planetary roller screw drives. Among these, planetary roller screws, compared to ball screws, have advantages such as higher load-bearing capacity and longer service life, and are increasingly valued and widely used, for example in electric cylinders, where a motor works in conjunction with the planetary roller screw pair to achieve telescopic motion. The main structure of a planetary roller screw pair includes a screw, a nut, and multiple rollers located between the screw and the nut. In a standard planetary roller screw pair, there is no axial movement between the rollers and the nut; the rollers and the nut move axially relative to the screw. To constrain the rollers to perform planetary motion (revolution and rotation), gear structures are usually machined on the outer circumference of both ends of the rollers, and internal gear rings are installed at both ends inside the nut. The meshing of the gears and gear rings provides constraint force on the movement of the rollers. However, due to the high precision requirements of planetary roller screw pairs, the structure and machining of the gears and gear rings are relatively complex and difficult, resulting in higher production costs. Utility Model Content

[0003] The purpose of this invention is to provide a planetary roller screw pair to solve the problem that the current planetary roller screw pair uses gears and gear rings to constrain the movement of the roller planets, which is difficult to process. The purpose of this invention is also to provide an electric cylinder that uses this planetary roller screw pair.

[0004] The technical solution of this utility model of planetary roller screw pair is:

[0005] The planetary roller screw pair includes a nut, a screw, and rollers. The rollers have limiting sections on both sides of their threaded sections. The diameter of the limiting sections is smaller than the diameter of the threaded sections. The threaded sections of the rollers are threadedly engaged with the nut and the screw. The limiting sections are structured in either of the following two forms: (1) The screw thread of the nut is opposite to the screw thread of the roller. The limiting sections and the corresponding limiting sections of the nut are provided with annular grooves around the axis. The inner diameter of the part of the nut with annular grooves is smaller than the inner diameter of the part with threads. The partial engagement between the annular groove of the roller and the two adjacent annular grooves of the nut constrains the roller. (2) The screw thread is opposite to the screw thread. The limiting sections and the corresponding limiting sections of the screw are provided with annular grooves around the axis. The inner diameter of the part of the screw with annular grooves is larger than the inner diameter of the part with threads. The partial engagement between the annular groove of the roller and the two adjacent annular grooves of the screw constrains the roller.

[0006] Beneficial effects: This utility model modifies existing planetary roller screw pairs by adding a smaller diameter limiting section to the rollers and an annular groove to the limiting section. Corresponding annular grooves are also provided at corresponding locations on the nut or screw. After the nut, screw, and rollers are assembled, the roller threads form threaded engagements with the nut and screw threads, respectively. The annular grooves of the nut or screw and rollers also engage, with the portion between two adjacent annular grooves on one roller extending into the annular groove on the other and able to rotate within it. The engagement between the annular groove areas of the nut and roller, or the screw and roller, does not interfere with the threaded engagement. During rotation of the nut or screw... When the annular grooves engage, the rollers are constrained, causing them to revolve and rotate around the lead screw. When the nut's annular groove engages with the roller's annular groove, there is no axial movement between the nut and the rollers, converting the nut's rotational motion into the lead screw's linear motion. Conversely, when the lead screw's annular groove engages with the roller's annular groove, there is no axial movement between the lead screw and the rollers, converting the nut's rotational motion into the lead screw's linear motion, with the rollers and lead screw moving axially relative to the nut. This structure, which utilizes the engagement of annular grooves to constrain the planetary motion of the rollers, is relatively simple to manufacture, easy to implement, and convenient to install, thus reducing production costs.

[0007] Furthermore, each roller is fitted with a cage at both ends, and the same end of each roller is mounted on the same cage to maintain their relative positions.

[0008] Furthermore, the two cages are fixedly connected by a connecting rod, which is located between the nut and the lead screw. There is a space between the nut and the lead screw for the cage to be installed and rotated. The nut or lead screw is provided with a structure for axially limiting the cage.

[0009] Furthermore, multiple rollers and multiple connecting rods are staggered and evenly distributed in the circumferential direction.

[0010] Furthermore, the rollers use single-start threads, and the screw pitch, roller pitch, and nut pitch are the same. The diameter of the screw thread section is an integer multiple of the roller thread section diameter, and this multiple is equal to the number of starts of the screw thread.

[0011] Furthermore, the rollers use single-start threads, while the nuts use multi-start threads, with the number of thread starts in the nut being n. p The number of threads on the lead screw is n s , where n p =n s +2.

[0012] Furthermore, the outer circumferential surface of the limiting section of the roller is machined with three or more of the aforementioned annular grooves, and the inner circumferential surfaces of both ends of the nut or the outer circumferential surfaces of both ends of the lead screw are correspondingly machined with multiple of the aforementioned annular grooves. The annular grooves on the roller are misaligned with the annular grooves on the nut or lead screw to form an engagement and constrain the roller.

[0013] The technical solution of the electric cylinder of this utility model is as follows:

[0014] An electric cylinder includes a cylinder body, a motor, and a planetary roller screw pair installed in the cylinder body. The motor is connected to the planetary roller screw pair for transmission. The planetary roller screw pair includes a nut, a screw, and rollers. Limiting sections are provided on both sides of the threaded section of the roller. The diameter of the limiting section is smaller than the diameter of the threaded section. The threaded section of the roller is threadedly engaged with the nut and the screw. The structure of the limiting section adopts either of the following two forms: (1) The thread direction of the nut is opposite to that of the roller thread. The corresponding limiting sections of the limiting section and the nut are located at the same position. All are provided with annular grooves around the axis. The inner diameter of the part of the nut with annular groove is smaller than the inner diameter of the part with thread. The annular groove of the roller and the part between two adjacent annular grooves of the nut partially fit together to constrain the roller. (2) The screw thread direction is opposite to the roller thread direction. The corresponding limit section of the limit section and the screw are provided with annular grooves around the axis. The inner diameter of the part of the screw with annular groove is larger than the inner diameter of the part with thread. The annular groove of the roller and the part between two adjacent annular grooves of the screw partially fit together to constrain the roller.

[0015] Beneficial Effects: This utility model modifies the elements of the existing planetary roller screw pair of an electric cylinder by setting a smaller diameter limiting section on the roller and an annular groove on the limiting section. Corresponding annular grooves are also set at the corresponding positions of the nut or screw. After the nut, screw, and roller are assembled together, the roller thread forms a threaded engagement with the nut thread and the screw thread, respectively. The annular grooves of the nut or screw and the roller also engage, with the portion between two adjacent annular grooves on one extending into the annular groove on the other and able to rotate within the groove. The engagement between the annular groove areas of the nut and roller or the screw and roller does not interfere with the threaded engagement. During the rotation of the nut or screw... During rotation, the rollers are constrained by the fit of the annular groove regions, causing them to revolve and rotate around the lead screw. When the nut annular groove region fits with the roller annular groove region, there is no axial movement between the nut and the rollers, allowing the rotational motion of the nut to be converted into the linear motion of the lead screw. When the lead screw annular groove region fits with the roller annular groove region, there is no axial movement between the lead screw and the rollers, allowing the rotational motion of the nut to be converted into the linear motion of the lead screw, with the rollers and lead screw moving axially relative to the nut together. This structure, which uses the fit between annular grooves to constrain the planetary motion of the rollers, is relatively simple to manufacture, easy to implement, and convenient to install, thus helping to reduce production costs.

[0016] Furthermore, each roller is fitted with a cage at both ends, and the same end of each roller is mounted on the same cage to maintain their relative positions.

[0017] Furthermore, the two cages are fixedly connected by a connecting rod, which is located between the nut and the lead screw. There is a space between the nut and the lead screw for the cage to be installed and rotated. The nut or lead screw is provided with a structure for axially limiting the cage.

[0018] Furthermore, multiple rollers and multiple connecting rods are staggered and evenly distributed in the circumferential direction.

[0019] Furthermore, the rollers use single-start threads, and the screw pitch, roller pitch, and nut pitch are the same. The diameter of the screw thread section is an integer multiple of the roller thread section diameter, and this multiple is equal to the number of starts of the screw thread.

[0020] Furthermore, the rollers use single-start threads, while the nuts use multi-start threads, with the number of thread starts in the nut being n. p The number of threads on the lead screw is n s , where n p =n s +2.

[0021] Furthermore, the outer circumferential surface of the limiting section of the roller is machined with three or more of the aforementioned annular grooves, and the inner circumferential surfaces of both ends of the nut or the outer circumferential surfaces of both ends of the lead screw are correspondingly machined with multiple of the aforementioned annular grooves. The annular grooves on the roller are misaligned with the annular grooves on the nut or lead screw to form an engagement and constrain the roller.

[0022] Furthermore, the lead screw of the planetary roller screw pair is used to form the telescopic rod of the electric cylinder. The motor is a frameless motor mounted on the cylinder body. The stator of the frameless motor is fixed to the cylinder body, and the rotor is fixed to the nut of the planetary roller screw pair. The nut of the planetary roller screw pair is rotatably mounted on the cylinder body through bearings. The end of the cylinder body through which the telescopic rod passes is the rod end, and both the frameless motor and the nut are mounted on the rod end.

[0023] Furthermore, a guide block is installed at one end of the lead screw located inside the cylinder, and the guide block is guided and engaged with the inner wall of the cylinder along the axial direction of the lead screw. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of an embodiment of the electric cylinder of this utility model;

[0025] Figure 2 for Figure 1 A schematic diagram of the internal structure of the electric cylinder in the diagram;

[0026] Figure 3 for Figure 2 A schematic diagram of the mounting base after removing the planetary roller screw assembly;

[0027] Figure 4 for Figure 2 A schematic diagram of a planetary roller screw pair;

[0028] Figure 5 for Figure 4 A schematic diagram of the nut in the diagram;

[0029] Figure 6 for Figure 2 A schematic diagram of the rollers in the process;

[0030] Figure 7 for Figure 2 A schematic diagram of the installation of the cage and connecting rod;

[0031] Figure 8 for Figure 2 A schematic diagram of the lead screw in the circuit.

[0032] In the diagram: 11. Cylinder barrel; 12. Cylinder seat; 13. Mounting seat; 14. Fixed tie rod; 21. Lead screw; 22. Nut; 221. Nut thread; 222. Nut annular groove; 23. Roller; 231. Roller thread; 232. Roller annular groove; 24. Cage; 25. Connecting rod; 30. Frameless motor; 40. Bearing; 51. Large washer; 52. Small washer; 60. Guide block. Detailed Implementation

[0033] The basic concept of this utility model of planetary roller screw pair is to use the nut or screw and the annular groove of the roller to form a misaligned fit, thereby constraining the roller to make it move in a planetary manner, simplifying the structure, facilitating processing, and reducing the difficulty of manufacturing.

[0034] The present invention will be described in detail below with reference to specific embodiments.

[0035] Embodiments of the electric cylinder of this utility model:

[0036] This electric cylinder uses a planetary roller screw pair to achieve telescopic motion. The specific structure is as follows: Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, the electric cylinder includes a cylinder body, a motor, and a planetary roller screw pair. The cylinder body includes a cylinder barrel 11, a cylinder seat 12, and a mounting base 13. The motor is a frameless motor 30 and includes a driver. The planetary roller screw pair includes a screw 21, a nut 22, and rollers 23. The frameless motor 30 and the driver are integrated with the planetary roller screw pair to form a linear motion cylinder.

[0037] The cylinder base 12 and mounting base 13 are respectively fixed to both ends of the cylinder barrel 11 and are fixedly connected by multiple fixed tie rods 14 surrounding the cylinder barrel 11. The cylinder base 12 is closed and has fixing holes for fixing to other components. The mounting base 13 is a ring structure, and a frameless motor 30 and a planetary roller screw pair are installed in its central hole, so that the planetary roller screw pair is installed in the cylinder body, and the frameless motor 30 is drivenly connected to the planetary roller screw pair. The screw 21 of the planetary roller screw pair is used to form the telescopic rod of the electric cylinder. The end of the cylinder body through which the telescopic rod passes is the rod end. The stator of the frameless motor 30 is fixed to the cylinder body, and the rotor is fixed to the nut 22 of the planetary roller screw pair. The nut 22 of the planetary roller screw pair is rotatably installed on the rod end of the cylinder body through a bearing 40. The end where the mounting base 13 is located is the rod end of the cylinder body, which helps to simplify the structure and ensure reliable use. In other embodiments, the frameless motor and nut can also be installed at the other end of the cylinder body, as long as the stroke meets the requirements.

[0038] In this embodiment, bearing 40 is a crossed roller bearing, and nut 22 in the planetary roller screw pair is mounted on mounting base 13 via the crossed roller bearing. Only one crossed roller bearing is needed, reducing the overall size of the electric cylinder while achieving relatively ideal radial, axial, and bending load-bearing capacity. In other embodiments, other types of slewing bearings capable of withstanding axial forces can also be used.

[0039] With the side closest to the inner cavity of cylinder 11 as the axial inner side and the side furthest from the inner cavity of cylinder 11 as the axial outer side, the inner circumferential surface of the mounting base 13 is provided with a step. The bearing 40 is installed on the axial outer side of the step, and a large washer 51 is installed on the axial outer side of the bearing 40. The large washer 51 is fixed on the mounting base 13, and the outer diameter of the large washer 51 is adapted to the inner diameter of the corresponding part of the mounting base 13. It is fixedly connected by radially installed screws. The stepped surface of the inner circumferential surface of the mounting base 13 and the large washer 51 cooperate with each other on both sides of the bearing 40 to axially limit the outer ring of the bearing 40. The frameless motor 30 is installed inside the bearing 40 and spaced apart from the bearing 40. The stator of the frameless motor 30 is fixed to the inner wall of the mounting base 13.

[0040] The outer circumferential surface of nut 22 is a stepped surface with an inner step and an outer step. The outer diameter of the outer step is larger than that of the inner step. The rotor of frameless motor 30 is fixedly sleeved on the circumferential surface of the inner step of nut 22. The inner ring of bearing 40 is fixedly sleeved on the circumferential surface of the outer step of nut 22. A stop ring platform is also provided on the outer side of bearing 40 on nut 22. A small washer 52 is installed on the inner side of bearing 40 on nut 22. The small washer 52 is fixedly sleeved on the circumferential surface of the outer step of nut 22 and can be fixed by radial screws. The small washer 52, in conjunction with the stop ring platform, axially limits the inner ring of bearing 40 on both sides of bearing 40.

[0041] The outer end of the lead screw 21 extends out of the cylinder body and is provided with a fastening thread or screw hole for easy connection between the lead screw 21 and moving parts. A guide block 60 is installed at the inner end of the lead screw 21 located inside the cylinder 11. The guide block 60 and the inner wall of the cylinder 11 are axially guided and engaged along the lead screw 21, increasing the bending resistance of the entire cylinder body. The guide block 60 has axial through holes, with multiple through holes distributed circumferentially, allowing connection between the two sides. A frameless motor 30 is used as the power source. The motor rotor is securely connected to the nut 22 of the planetary roller lead screw pair. The nut 22 rotates with the rotor, and the nut 22 drives the lead screw 21 to move linearly via the rollers 23. The thread length of the lead screw 21 meets the stroke requirements of the telescopic rod.

[0042] Combination Figure 5 , Figure 6 , Figure 7 , Figure 8 The specific structure of the planetary roller screw pair is described below. In this embodiment, the roller 23 of the planetary roller screw pair has limiting sections on both sides of its threaded section. The diameter of the limiting section is smaller than the diameter of the threaded section. The roller thread 231 is located on its threaded section. The threaded section of the roller 23 is threadedly engaged with the nut 22 and the screw 21. The rotation direction of the nut thread 221 is opposite to that of the roller thread 231. The limiting sections of the roller 23 and the corresponding limiting sections of the nut 22 are provided with annular grooves around the axis. The annular groove on the roller 23 is called the roller annular groove 232, and the annular groove on the nut 22 is called the nut annular groove 222. The inner diameter of the part of the nut 22 with the annular groove is smaller than the inner diameter of the part with the thread. The annular groove on one of the nut 22 and the part between two adjacent annular grooves on the other roller 23 are inserted to form a fitting. The roller 23 is constrained by the axial limiting fit between the annular groove of the roller 23 and the part between two adjacent annular grooves of the nut 22.

[0043] After the nut 22, lead screw 21, and roller 23 are assembled together, the roller thread 231 forms a threaded fit with the nut thread 221 and the lead screw thread 21, respectively. The annular groove regions of the nut 22 and roller 23 form a misaligned engagement, allowing relative rotation without interfering with the threaded fit. When the nut 22 rotates, the annular groove constrains the roller 23, causing it to revolve and rotate around the lead screw 21. There is no axial movement between the nut 22 and roller 23, converting the rotational motion of the nut 22 into the linear motion of the lead screw 21. The annular groove constraint allows for the bearing of larger axial loads. This structure, which uses annular grooves to constrain the planetary motion of the roller 23, is relatively simple to manufacture, easy to implement, and convenient to install, thus reducing production costs.

[0044] In this embodiment, one form of the roller limiting section structure is that the roller annular groove 232 and the nut annular groove 222 cooperate to constrain the roller. The nut 22 and the roller 23 have no axial movement, while the roller and the nut together have relative axial movement with the lead screw. In other embodiments, the roller limiting section structure can also take another form, that is: the screw thread direction is opposite to the roller thread direction, and the corresponding limiting sections of the limiting section and the lead screw are provided with annular grooves around the axis. The inner diameter of the part of the lead screw with annular grooves is larger than the inner diameter of the part with threads. The roller annular groove and the part between two adjacent annular grooves of the lead screw cooperate to constrain the roller. At this time, the annular groove area of ​​the lead screw and the annular groove area of ​​the roller form a misaligned fit. The lead screw and the roller have no axial movement, while the roller and the lead screw together have axial movement relative to the nut. At this time, the axial dimension of the nut is large, and the length of its threaded part meets the axial movement stroke of the lead screw and the roller together relative to the nut.

[0045] In this embodiment, the roller annular groove 232 is formed by machining an annular groove on the limiting section of the roller 23. Correspondingly, the nut annular groove 222 is formed by machining an annular groove on a corresponding part of the inner wall of the nut 22. The portion between two adjacent annular grooves on one of the nut and roller forms a fitting protrusion that extends into the annular groove on the other. The cross-sections of both the nut annular groove 222 and the roller annular groove 232 are triangular, and the fitting protrusion formed between two adjacent annular grooves is triangular and fits the annular grooves. The annular grooves are machined in three or more places on the outer circumferential surface of the limiting section of the roller 23, and multiple annular grooves are correspondingly provided on the inner circumferential surface of the nut 22, thereby improving structural stability.

[0046] The roller 23 has a threaded section of roller thread 231 that connects to a limiting section with roller annular groove 232. The threaded section is located in the middle, and the two limiting sections are located near the two ends. The roller annular groove 232 is arranged around the axis of the roller 23, and the annular grooves in the same section are evenly distributed axially. The axial length of the threaded section is greater than the axial length of the limiting section, and the maximum diameter of the limiting sections at both ends of the roller 23 is smaller than the nominal diameter of the threaded section, to avoid interference between the roller 23 groove and the screw 21 thread. Correspondingly, the inner diameter of the portion of the inner circumference surface of the nut 22 with nut thread 221 is larger, while the inner diameter of the portion with nut annular groove 222 is smaller. The nut thread 221 is adapted to the roller thread 231, and the two sections of nut annular groove 222 are adapted to the two sections of roller annular groove 232.

[0047] The dimensions and number of threads of the rollers 23, nut 22, and screw 21 are selected and set according to the load-bearing capacity, high-speed adaptability, stability, and rigidity of the planetary roller screw pair.

[0048] In this embodiment, the roller 23 adopts a single-start thread. The pitch of the lead screw 21, the pitch of the roller 23, and the pitch of the nut 22 are the same. The diameter of the threaded portion of the lead screw 21 is an integer multiple of the diameter of the 1-segment diameter of the roller thread 23. The nominal diameter φ of the lead screw 21 thread is...g It is a roller thread with a nominal diameter of φ231. zw The multiple m, where m is a positive integer, is equal to the number of threads n of the 21-thread screw. s That is, m=n s This ensures that the roller 23 can roll smoothly on the lead screw 21.

[0049] The number of threads n of nut thread 221 p Unlike the roller thread 231, the nut thread 221 is a multi-start thread, and the number of starts of the nut thread 221 depends on the number of starts (n) of the lead screw 21. s n p =n s +2, ensuring that there is no axial movement between the nut 22 and the roller 23 during transmission.

[0050] To ensure the stability of the roller 23's movement, a cage 24 is installed at each end of the roller 23. The same end of each roller 23 is mounted on the same cage 24 to maintain the relative position of each roller 23. The cage 24 is annular, with a central hole through which the lead screw 21 passes. Both ends of the roller 23 are also provided with a smooth shaft section, located on the side of the limiting section away from the threaded section. The cage 24 has mounting holes for mounting the smooth shaft section of the roller 23. The roller 23 can rotate relative to the cage 24, and simultaneously drives the cage 24 to rotate within the nut 22 during its revolution.

[0051] Two retainers 24 are fixedly connected by a connecting rod 25. The connecting rod 25, retainers 24, and each roller 23 are located between a nut 22 and a lead screw 21. A space is provided between the nut 22 and the lead screw 21 for the retainers 24 to be inserted and rotated. The nut 22 has a structure for axially limiting the retainers 24. This structure includes stop steps and slots located on the inner walls at both ends of the nut 22. The retainers 24 are fitted into the nut 22, with inward stop formed by the stop steps and outward stop formed by a retaining spring installed in the slot, preventing axial movement of the retainers 24. The two retainers 24 have fixing holes for fixed connection at both ends of the connecting rod 25. The connecting rod 25 fixes the two retainers 24 together, and the multiple evenly distributed rollers 23 are combined with the two retainers 24, resulting in a stable structure. In other embodiments, the connecting rod may be omitted.

[0052] Multiple rollers 23 and multiple connecting rods 25 are staggered and evenly distributed in the circumferential direction. Mounting holes and fixing holes are evenly distributed on the cage 24. The number of mounting holes is the same as the number of rollers 23, and the number of fixing holes is the same as the number of connecting rods 25. The number of connecting rods 25 is the same as the number of rollers 23. The diameter of the connecting rods 25 is smaller than the diameter of the rollers 23. The even distribution of all connecting rods 25 and rollers 23 in the circumferential direction contributes to smooth operation. In other embodiments, different numbers of connecting rods can be provided as needed.

[0053] An embodiment of the planetary roller screw pair of this utility model:

[0054] The planetary roller screw pair in this embodiment has the same structure as the planetary roller screw pair described in the above embodiment of the electric cylinder, and will not be repeated here.

[0055] Finally, it should be noted that the above description is only a preferred embodiment of this utility model and is not intended to limit this utility model. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still make modifications to the technical solutions described in the foregoing embodiments without creative effort, or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A planetary roller screw pair, characterized in that, The roller includes a nut, a lead screw, and rollers. The rollers are provided with limiting sections on both sides of their threaded sections. The diameter of the limiting sections is smaller than the diameter of the threaded sections. The threaded sections of the rollers are threadedly engaged with the nut and the lead screw. The limiting sections are constructed in either of the following two ways: (1) The thread direction of the nut is opposite to that of the roller. The limiting sections and the corresponding limiting sections of the nut are provided with annular grooves around the axis. The inner diameter of the part of the nut with annular grooves is smaller than the inner diameter of the part with threads. The roller's annular grooves and the two adjacent annular grooves of the nut partially engage to constrain the roller. (2) The thread direction of the lead screw is opposite to that of the roller. The limiting sections and the corresponding limiting sections of the lead screw are provided with annular grooves around the axis. The inner diameter of the part of the lead screw with annular grooves is larger than the inner diameter of the part with threads. The roller's annular grooves and the two adjacent annular grooves of the lead screw partially engage to constrain the roller.

2. The planetary roller screw assembly according to claim 1, characterized in that, Each roller is fitted with a cage at both ends, and the same end of each roller is mounted on the same cage to maintain their relative positions.

3. The planetary roller screw pair according to claim 2, characterized in that, Two cages are fixedly connected by a connecting rod, which is located between a nut and a lead screw. There is a space between the nut and the lead screw for the cage to be inserted and rotated. The nut or lead screw has a structure for axially limiting the cage.

4. The planetary roller screw pair according to claim 3, characterized in that, Multiple rollers and multiple connecting rods are staggered and evenly distributed in the circumferential direction.

5. The planetary roller screw assembly according to any one of claims 1-4, characterized in that, The rollers use single-start threads. The screw pitch, roller pitch, and nut pitch are the same. The diameter of the screw thread section is an integer multiple of the roller thread section diameter, and this multiple is equal to the number of starts of the screw thread.

6. The planetary roller screw assembly according to any one of claims 1-4, characterized in that, The rollers use single-start threads, while the nuts use multi-start threads, with n being the number of thread starts on the nut. p The number of threads on the lead screw is n s , where n p =n s +2.

7. The planetary roller screw assembly according to any one of claims 1-4, characterized in that, The roller has three or more annular grooves machined on its outer peripheral surface of the limiting section. The inner peripheral surfaces of the two ends of the nut or the outer peripheral surfaces of the two ends of the lead screw have multiple annular grooves machined on them. The annular grooves on the roller are misaligned with the annular grooves on the nut or lead screw to form an engagement and constrain the roller.

8. An electric cylinder, comprising a cylinder body, a motor, and a planetary roller screw assembly mounted within the cylinder body, wherein the motor is connected to the planetary roller screw assembly via a transmission connection, characterized in that, The planetary roller screw pair is the planetary roller screw pair described in any one of claims 1-7.

9. The electric cylinder according to claim 8, characterized in that, The lead screw of the planetary roller screw pair is used to form the telescopic rod of the electric cylinder. The motor is a frameless motor mounted on the cylinder body. The stator of the frameless motor is fixed to the cylinder body, and the rotor is fixed to the nut of the planetary roller screw pair. The nut of the planetary roller screw pair is rotatably mounted on the cylinder body through a bearing. The end of the cylinder body through which the telescopic rod passes is the rod end, and both the frameless motor and the nut are mounted on the rod end.

10. The electric cylinder according to claim 9, characterized in that, A guide block is installed at one end of the lead screw inside the cylinder, and the guide block is guided and engaged with the inner wall of the cylinder along the axial direction of the lead screw.

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