Planetary roller lead screw structure, machining method and assembling method of planetary roller lead screw structure

Abstract

The planetary roller lead screw structure comprises a nut sleeve, a roller set and a lead screw, the roller set comprises a plurality of rollers, each roller comprises a first section and a second section, the nut sleeve comprises an internal thread part, the lead screw is in threaded fit with the first section, and the first section is in threaded fit with the internal thread part; the planetary roller lead screw structure comprises a gear ring, the gear ring is matched with the second section in a meshed mode, and the gear ring and the nut sleeve are an integrated piece. In the invention, the gear ring and the nut sleeve are integrated, so that the step of interference assembly of the gear ring and the nut sleeve is reduced, and the assembly convenience is improved.

Description

Technical Field

[0001] This application relates to the field of actuators, and particularly to the planetary roller screw structure of an actuator. Background Art

[0002] An actuator includes a planetary roller screw structure, and the output action of the actuator is realized through the planetary roller screw structure. In related technologies, the planetary roller screw structure includes a nut sleeve, a screw rod, and a roller group composed of multiple rollers. The roller group is in threaded cooperation with the nut sleeve and the screw rod respectively, and also includes a gear ring. The gear ring is in meshing cooperation with the rollers. During assembly, the gear ring needs to be interference-fitted with the nut sleeve, and then a part of the rollers is in meshing cooperation with the gear ring, making the assembly process rather troublesome. Summary of the Invention

[0003] This application provides a planetary roller screw structure, which includes a nut sleeve, a roller group, and a screw rod. The roller group includes multiple rollers. Each roller includes a first section and a second section. The nut sleeve includes an internal thread portion. The screw rod is in threaded cooperation with the first section, and the first section is in threaded cooperation with the internal thread portion.

[0004] The planetary roller screw structure includes a gear ring, which is in meshing cooperation with the second section, and the gear ring and the nut sleeve are an integral part.

[0005] In this application, since the gear ring and the nut sleeve are an integral part, the step of interference-fitting the gear ring and the nut sleeve is reduced, thereby improving the convenience of assembly.

[0006] This application provides a processing method for a planetary roller screw structure. A cylindrical workpiece is provided, and an internal thread portion that can be in threaded cooperation with the rollers is milled on the inner wall of the cylindrical workpiece. Along the axial direction of the cylindrical workpiece, a gear ring that can be in meshing cooperation with the rollers is milled on the inner wall of the cylindrical workpiece, and the cylindrical workpiece is processed to form a nut sleeve.

[0007] In this application, by milling the internal thread portion and the gear ring on the cylindrical workpiece, the nut sleeve and the gear ring are an integral part, thereby reducing the assembly steps of the gear ring and the nut sleeve during subsequent assembly and improving the convenience of assembly.

[0008] This application also provides an assembly method for a planetary roller screw structure. A nut sleeve, rollers, and a screw rod are provided. The internal thread portion and the gear ring are pre-milled on the inner wall of the nut sleeve. A cage is provided and placed into the nut sleeve. When the rollers are correspondingly installed into the cage, the rollers are in threaded cooperation with the internal thread portion and in meshing cooperation with the gear ring, and then the screw rod is assembled into the nut sleeve and in threaded cooperation with the rollers.

[0009] In this application, when assembling the planetary roller screw structure, while the roller is in threaded fit with the internal thread portion, it is also in meshing fit with the gear ring, reducing the steps of connecting the gear ring and the nut sleeve, thereby improving the convenience of assembly. Description of the Drawings

[0010] Figure 1 is a three-dimensional view of the planetary roller screw structure in this application;

[0011] Figure 2 is a cross-sectional view of the planetary roller screw structure in this application;

[0012] Figure 3 is a three-dimensional view of the cage and the roller set in cooperation in this application;

[0013] Figure 4 is a side view of the cage and the roller set in cooperation in this application;

[0014] Figure 5 is a front view of the cage and the roller set in cooperation in this application;

[0015] Figure 6 is a cross-sectional view of the cage and the roller set in cooperation in this application;

[0016] Figure 7 is a three-dimensional view of the cage in this application;

[0017] Figure 8 is an exploded view of the planetary roller screw structure in this application;

[0018] Figure 9 is a cross-sectional view of the planetary roller screw structure in another embodiment of this application. Detailed Description of the Embodiments

[0019] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0020] It should be clear that the described embodiments are only a part of the embodiments of this application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts shall fall within the scope of protection of this application.

[0021] In the related art, the actuator includes a planetary roller screw structure. The planetary roller screw structure includes a nut sleeve, a roller set composed of a plurality of rollers, and a screw rod. The roller set is in threaded cooperation with the nut sleeve, and the roller set is also in threaded cooperation with the screw rod. The roller includes a threaded section and a gear section, and the threaded section mainly cooperates with the screw rod and the nut sleeve in terms of threading. During the machining process, a tool withdrawal transition section will be left between the gear section and the threaded section so that when machining one of the gear section and the threaded section, the other will not be damaged. The planetary roller screw structure further includes a cage and a retaining ring. When the roller is machined, on its axial direction, a part for connecting the cage is reserved on the side where the gear section is far from the threaded section. At the same time, in order to limit and fix the cage in the axial direction, a retaining ring is provided on one side of the cage. However, the size of the planetary roller screw structure in the axial direction will increase, and further increase the structural size of the actuator as a whole in the axial direction.

[0022] More specifically, the cage is annular, and an arc-shaped opening is formed on its inner ring wall for installing, positioning, and limiting the rollers. When connecting the rollers to the cage, the rollers are placed at the opening position and can be limited in the circumferential direction. Therefore, during assembly, additional tooling is required to temporarily fix the rollers. Not only does it require providing tooling, but also since additional tooling is needed to fix and limit the cage, the space for the tooling for fixing the rollers is very limited, making the assembly very troublesome. (To facilitate understanding of the technical features in this application and those in the related art, the same technical feature names in this application are used as much as possible for the technical features described in the related art. Similarly, to distinguish the technical features of the related art and this application, the descriptions of the technical features in the related art are not numbered.)

[0023] In the first embodiment, the present application provides a planetary roller screw structure, as Figure 1 、 2 shown in FIGS. 6 to 8, including a nut sleeve 1, a roller set 2, and a screw rod 3. The screw rod 3 is in threaded cooperation with the roller set 2, and the roller set 2 is in threaded cooperation with the inner wall of the nut sleeve 1; the planetary roller screw structure includes a cage 5. The roller set 2 includes a plurality of rollers 200. The cage 5 is connected to the rollers 200. The cage 5 has a card slot 501, and at least part of the roller 200 is located in the card slot 501; the cage 5 includes a retaining arm 502. The cage 5 has an opening 503. At least part of the retaining arm 502 forms the wall of the opening 503. The minimum distance of the opening 503 is smaller than the diameter of the part of the roller 200 located in the card slot 501.

[0024] The threaded fit between the roller 200 and the lead screw 3, the threaded fit between the roller 200 and the nut sleeve 1, and the principle of the planetary roller screw structure are the same as those in the related art, and will not be elaborated here. The setting of the retaining arm 502 can limit the roller 200 when it is assembled and connected to prevent the roller 200 from disengaging during the assembly process. The rollers 200 are installed one by one on the cage 5 during installation, specifically installed in the card slots 501 of the cage 5. The setting of the card slots 501 can play a role in positioning the rollers 200 during installation on the one hand, and can also play a certain limiting role in the circumferential direction of the rollers 200 on the other hand, preventing uneven arrangement of the multiple rollers 200, resulting in misalignment or interference.

[0025] During actual installation, align the roller 200 with the opening 503 of the cage 5, and then snap the roller 200 into the card slot 501 from the opening 503. At this time, the retaining arm 502 can limit the roller 200 to prevent it from falling off. Without the retaining arm 502, during the installation process, after the roller 200 is placed in the card slot 501, there is no limit, and it is very easy to fall off from the card slot 501, reducing the assembly efficiency. Otherwise, external tooling needs to be used to temporarily position the roller 200, which undoubtedly further reduces the assembly operation space and increases the assembly difficulty.

[0026] The roller 200 includes a transition section 203, and the transition section 203 is connected to the cage 5. The transition section 203 is at least partially located in the card slot 501. In the radial direction of the roller 200, the retaining arm 502 can abut against the transition section 203. The roller 200 includes a first section 201 and a second section 202. The first section 201 is connected to the transition section 203, and the second section 202 is connected to the transition section 203. The transition section 203 is located between the first section 201 and the second section 202.

[0027] Specifically, when the cage 5 is assembled and connected to the roller 200, the cage 5 is connected to the transition section 203. The transition section 203 can facilitate the processing of one of the first section 201 and the second section 202 of the roller set 2 without damaging the other. The first section 201 is in threaded fit with the nut sleeve 1, and the first section 201 is also in threaded fit with the lead screw 3, thereby realizing the transmission fit; it is connected to the transition section 203, thereby reducing the space occupied in the axial direction and reducing the size in the axial direction.

[0028] Among them, compared with the first section 201 and the second section 202, the diameter of the transition section 203 is smaller. As a result, steps are formed between the transition section 203 and the first section 201, and between the transition section 203 and the second section 202. When the cage 5 is connected to the transition section 203, the steps formed between them can play an axial limiting role on the cage 5. Moreover, when the cage 5 is located in this part of the transition section 203, while reducing the axial dimension, it will not affect the thread fit between the first section 201 and the nut sleeve 1 or the meshing between the second section 202 and the gear ring 4.

[0029] As Figure 6 and 7 shown, the retaining arm 502 is an elastic member. The number of retaining arms 502 is two. The opening 503 is located between the two retaining arms 502. The transition section 203 is cylindrical. The minimum distance between the two retaining arms 502 is less than the diameter of the transition section 203.

[0030] The retaining arm 502 is an elastic member, which facilitates the roller 200 to be snapped into the card slot 501 from the opening 503. If the retaining arm 502 is a rigid structure, the roller 200 cannot be installed. The retaining arm 502 and the main body forming the cage 5 are an integral part, thus jointly forming the cage 5. Moreover, the gap between the two retaining arms 502 forms the opening 503. The minimum distance between the two retaining arms 502 is less than the diameter of the transition section 203, which can prevent the roller 200 from easily falling off the card slot 501, and the retaining arm 502 will abut and limit the transition section 203.

[0031] Among them, the elasticity of the retaining arm 502 can satisfy the following relationship with the size of the opening 503. The greater the elastic deformation of the retaining arm 502, the smaller the size of the opening 503. The smaller the elastic deformation of the retaining arm 502, the larger the size of the opening 503. Because the roller 200 has a certain weight, it can prevent the roller 200 from falling off during the assembly process and also facilitate the installation. For example, when the elastic deformation is small and its deformation displacement is small, if the opening of the opening 503 is small, a large external force is required to press or snap the roller 200 into the card slot 501 during assembly, which is not only inconvenient for assembly but may also cause damage and deformation of the structure.

[0032] Define the area of the transition section 203 as S. On the projection plane perpendicular to the axial direction of the roller 200, define the area of the region enclosed by the projection of the connection line between the two retaining arms 502 and the wall forming the card slot 501 as S1. Among them, S and S1 satisfy the following relationship: S1 > S / 2.

[0033] The cage 5 is integrally annular. In the axial direction of the cage 5, the card slot 501 penetrates through the cage 5. When viewed from the axial direction of the cage 5, the card slot 501 is generally circular, and the wall forming the card slot 501 can also fit with the transition section 203. The area enclosed by the connection line between the wall of the card slot 501 and the two retaining arms 502 is larger than half of the cross-sectional area of the transition section 203. Thus, when the transition section 203 is assembled into the card slot 501, the wall forming the card slot 501 and the retaining arms 502 can surround most of the transition section 203, which can further improve the fixing and limiting effects on the rollers 200. At the same time, during the assembly process, there is no need to temporarily support the rollers 200 with additional tooling. During the assembly, there is a hoop action on the transition section 203, and then the limiting effect is achieved.

[0034] If the area enclosed by the connection line between the wall of the card slot 501 and the two retaining arms 502 is less than half of the cross-sectional area of the transition section 203, although the circumferential limiting of the rollers 200 can still be achieved, the effect is poor. And during the assembly, most of the transition section 203 cannot be located within the card slot 501, and the retaining arms 502 cannot limit the transition section 203 to achieve the hoop action. It is still necessary to fix multiple rollers 200 with additional tooling. Otherwise, the positions of the rollers 200 cannot be fixed and they are likely to slide out and fall from the card slot 501.

[0035] The cage 5 is annular. In the circumferential direction of the cage 5, the rollers 200 are evenly spaced, and the roller group 2 is arranged in an annular shape. The maximum diameter of the cage 5 is smaller than the maximum diameter of the roller group 2.

[0036] Multiple rollers 200 are evenly spaced in the circumferential direction and enclose an annular roller group 2. The maximum diameter of the roller group 2 is larger than the maximum diameter of the cage 5, so that when the roller group 2 is threadedly engaged with the nut sleeve 1, the edge part of the cage 5 will not touch the inner wall of the nut sleeve 1, and no interference and wear will occur.

[0037] The planetary roller screw structure includes a gear ring 4. The second section 202 has an external tooth part, and the gear ring 4 includes an internal tooth part 401. The internal tooth part 401 is meshed and cooperated with the external tooth part. In this application, the tooth part mentioned refers to a gear, and the meshed cooperation also refers to the meshing between the teeth of the gears.

[0038] The maximum diameter of the cage 5 can be greater than the minimum diameter of the gear ring 4, but not greater than the maximum diameter of the gear ring 4, otherwise it will touch the inner wall of the nut sleeve 1 and cause interference and inability to install. Therefore, on the projection plane perpendicular to the axial direction of the gear ring 4, the projection of the cage 5 can coincide with the projection of the internal tooth part 401. The larger diameter of the cage 5 can make the overall strength of the cage 5 higher than that of a smaller diameter, and can also improve the structural stability, better limit and position the rollers, and will not affect the assembly. During specific assembly, the cage 5 can be first placed into the nut sleeve 1, then the rollers are assembled into the card slots 501, and while assembling, the rollers are threadedly engaged with the inner wall of the nut sleeve 1. Then the gear ring 4 can be assembled into the nut sleeve 1, and finally the lead screw 3 is assembled into the nut sleeve 1.

[0039] In another embodiment, if the gear ring 4 is to be installed first, then the maximum diameter of the cage 5 at this time should be less than the minimum diameter of the gear ring 4, otherwise the cage 5 cannot be installed into the nut sleeve 1 after the gear ring 4 is installed.

[0040] The nut sleeve 1 includes an internal thread part 101. In the axial direction of the nut sleeve 1, the internal thread part 101 extends from the inner wall of the nut sleeve 1 towards the direction close to the axis center line of the nut sleeve 1; the internal thread part 101 includes an end part 102, and the gear ring 4 abuts against the end part 102.

[0041] When the roller set 2 is threadedly engaged with the inner wall of the nut sleeve 1, it is mainly achieved by the threaded engagement between the first section 201 of the roller set 2 and the internal thread part 101. The internal thread part 101 protrudes from the inner wall surface of the nut sleeve 1. Therefore, the internal thread part 101 forms protruding end parts 102 at both ends thereof. The end parts 102 can limit the gear ring 4 and can also position the gear ring 4 during the assembly of the gear ring 4. There is no need to use an additional positioning tooling to position the gear ring 4, thereby reducing the error generated by the tooling during the assembly process, improving the accuracy of the fit between components, and thus improving the overall accuracy and transmission efficiency of the planetary roller screw structure.

[0042] As Figure 2 and 8 shown, the gear ring 4 includes a relief section 402. The relief section 402 is annular, and the relief section 402 is closer to the internal thread part 101 than the internal tooth part 401; in the direction from the inner wall of the gear ring 4 to the axis center line of the gear ring 4, the internal tooth part 401 protrudes from the relief section 402. In the projection along the radial direction of the gear ring 4, at least part of the projection of the cage 5 falls onto the projection of the relief section 402.

[0043] On the one hand, the function of the relief section 402 can keep the internal tooth portion 401 of the gear ring 4 at a certain distance from the internal thread portion 101, so that when the internal tooth portion 401 meshes with the second section 202, it will not interfere with the thread fit between the internal thread portion 101 and the first section 201. On the other hand, since there is a transition section 203 between the first section 201 and the second section 202, the transition section 203 has a certain length, and the transition section 203 needs to be connected to the cage 5. When the first section 201 corresponds to and mates with the internal thread portion 101, and the second section 202 corresponds to and mates with the internal tooth portion 401, the transition section 203 can correspond to the relief section 402, making the mating between the first section 201 and the internal thread portion 101, and between the second section 202 and the internal tooth portion 401 more precise. The first section 201 and the internal thread portion 101, the second section 202 and the internal tooth portion 401, and the transition section 203 and the relief section 402 are respectively in one-to-one corresponding mating in terms of positional relationship.

[0044] And the internal tooth portion 401 protrudes radially from the relief section 402, as Figure 2 and 8 shown, so that a stepped space is also formed between the internal tooth portion 401 and the relief section 402. In the radial direction, the stepped space provides more installation space for the cage 5. The transition section 203 and the relief section 402 also provide installation space for the cage 5 in the axial direction.

[0045] In the axial direction of the roller 200, there is a gap L between at least one of the first section 201 and the second section 202 and the cage 5.

[0046] The setting of the gap L allows for a certain production tolerance of the cage 5. Otherwise, in the axial direction, if the length of the transition section 203 is the same as the thickness of the cage 5, the production tolerance of the cage 5 needs to be controlled within a very small range, otherwise it is easy to cause the rollers 200 to be misaligned during installation, or even unable to be installed. This is not only inconvenient for installation but also increases the production cost.

[0047] In one embodiment, as Figures 3 to 5 shown, in the circumferential direction of the cage 5, a plurality of second sections 202 are arranged in a uniformly spaced annular pattern. The maximum diameter of the cage 5 is smaller than the maximum diameter of the annular arrangement of the plurality of second sections 202, and the maximum diameter of the cage 5 is smaller than the minimum diameter of the internal tooth portion 401.

[0048] Since the rollers 200 are arranged at equal intervals in a ring shape, the second sections 202 are also arranged at equal intervals in a ring shape. Therefore, after the multiple second sections 202 are arranged, they also have a maximum diameter. The maximum diameter of the cage 5 being smaller than the maximum diameter of the ring-shaped arrangement of the second sections 202 can prevent the edge of the cage 5 from exceeding the ring-shaped edge formed by the second sections 202 after being connected and assembled with the rollers 200, thereby reducing the interference of the cage 5 on other structures and improving the compactness of the structure.

[0049] In another embodiment, in the circumferential direction of the cage 5, the multiple second sections 202 are arranged at equal intervals in a ring shape. The maximum diameter of the cage 5 is larger than the maximum diameter of the ring-shaped arrangement of the multiple second sections 202, and the maximum diameter of the cage 5 is larger than the minimum diameter of the internal tooth portion 401.

[0050] The maximum diameter of the cage 5 can also be larger than the maximum diameter of the multiple second sections 202. In this case, the size of the cage 5 is larger, so that its overall structural strength is greater and the supporting effect on it is better.

[0051] During assembly, the gear ring 4 is in interference fit with the inner wall of the nut sleeve 1.

[0052] In the second embodiment, as Figure 9 shown, the present application also provides a planetary roller screw structure, including a nut sleeve 1, a roller set 2 and a screw rod 3. The roller set 2 includes a plurality of rollers 200. Each roller 200 includes a first section 201 and a second section 202. The nut sleeve 1 includes an internal thread portion 101. The screw rod 3 is in threaded engagement with the first section 201, and the first section 201 is in threaded engagement with the internal thread portion 101. The planetary roller screw structure includes a gear ring 4. The gear ring 4 is in meshing engagement with the second section 202, and the gear ring 4 and the nut sleeve 1 are an integral part.

[0053] The gear ring 4 and the nut sleeve 1 being an integral part can reduce the assembly of the gear ring 4 during the assembly process. In the related art, when assembling the gear ring 4, additional tooling is required to position the installation position of the gear ring 4, which will result in certain installation errors. Coupled with the possible production tolerances of the gear ring 4 itself, the assembly accuracy will be even worse. However, the gear ring 4 and the nut sleeve 1 being an integral part can also improve the assembly accuracy, thereby improving the cooperation and transmission accuracy between the components of the overall structure of the planetary roller screw structure.

[0054] The gear ring 4 includes an internal tooth portion 401. The internal tooth portion 401 is in meshing engagement with the second section 202. The planetary roller screw structure includes a cage 5. The cage 5 is connected to the rollers 200. The maximum diameter of the cage 5 is smaller than the minimum diameter of the internal tooth portion 401. On the projection plane perpendicular to the axial direction of the nut sleeve 1, the projection of the internal tooth portion 401 coincides with the projection of the internal thread portion 101.

[0055] It should be noted that since the gear ring 4 and the nut sleeve 1 are integral parts in this embodiment, the maximum diameter of the cage 5 should be smaller than the minimum diameter of the gear ring 4 to ensure that the cage 5 can be assembled into the nut sleeve 1. Otherwise, if the maximum diameter of the cage 5 is larger, the gear ring 4 will cause interference and obstruction to it. In addition, the projection of the internal tooth part 401 coincides with the projection of the internal thread part 101, that is, the size of the internal tooth part 401 is the same as the size of the internal thread part 101, and their diameters are the same in the radial direction because both are formed by machining on the inner wall of the nut sleeve 1 and both protrude from the inner wall of the nut sleeve 1, which facilitates the machining of the two.

[0056] In the axial direction of the nut sleeve 1, there is a relief area S between the internal tooth part 401 and the internal thread part 101. On the projection plane along the radial direction of the nut sleeve 1, at least part of the projection of the cage 5 falls into the relief area S.

[0057] The roller 200 includes a transition section 203. The first section 201 is connected to the transition section 203, the second section 202 is connected to the transition section 203, and the cage 5 is connected to the transition section 203. On the projection plane along the radial direction of the nut sleeve 1, the transition section 203 falls into the relief area S.

[0058] The setting of the relief area S can, on the one hand, also separate a certain distance between the internal tooth part 401 and the internal thread part 101, so that when machining one of them, it will not affect the other. At the same time, since there is also a transition section 203 between the first section 201 and the second section 202, the setting of the relief area S also enables them to correspond to each other one by one. Specifically, the first section 201 is in threaded fit with the internal thread part 101, and the external tooth part of the second section 202 is in meshing fit with the internal tooth part 401. The relief area S corresponds to the transition section 203 in position, so that the positional correspondence between the first section 201 and the internal thread part 101, and between the second section 202 and the internal tooth part 401 will be more accurate. And the relief area S also provides a larger installation space for the cage 5, improving the convenience of assembly between components.

[0059] In the circumferential direction of the cage 5, the rollers 200 are evenly spaced. The roller set 2 is in an annular shape, and the maximum diameter of the cage 5 is smaller than the maximum diameter of the roller set 2.

[0060] Among them, the cage 5 can adopt the cage 5 in the first embodiment. It should be noted that as described above, the maximum diameter of the cage 5 is smaller than the minimum diameter of the internal tooth part 401. And the maximum diameter of the cage 5 being smaller than the maximum diameter of the roller set 2 also has the same function as in the first embodiment, preventing the edge of the cage 5 from exceeding the roller set 2 and thus interfering with external components, etc., which will not be elaborated here.

[0061] The ring gear 4 has two, in the axial direction of the nut sleeve 1, and the two ring gears 4 are respectively located at both ends of the internal thread portion 101.

[0062] Similarly, the second section 202 and the transition section 203 also each have two, respectively corresponding to being located at both ends of the first section 201, thereby forming a stable fit and improving the stability of the overall structure.

[0063] The present application also provides a processing method for a planetary roller screw structure. A cylindrical workpiece is provided, and an internal thread portion 101 that can be threadedly engaged with the roller 200 is prefabricated on the inner side of the cylindrical workpiece. Along the axial direction of the cylindrical workpiece, a ring gear 4 that can be meshed with the roller 200 is prefabricated on the inner side of the cylindrical workpiece, and the cylindrical workpiece is processed to form the nut sleeve 1.

[0064] When milling one of the internal thread portion 101 or the ring gear 4 on the inner wall of the cylindrical workpiece, a spacing of the avoidance area S is left along the axial direction of the cylindrical workpiece. After milling the space of the avoidance area S on the inner wall of the cylindrical workpiece, then milling the other of the internal thread portion 101 or the ring gear 4 on the inner wall of the cylindrical workpiece.

[0065] Among them, for whether to prefabricate the internal thread portion 101 first or the ring gear 4 first, the processing sequence is not limited herein, but both are processed and formed in the same cylindrical workpiece, so that the ring gear 4 and the nut sleeve 1 are integral parts, thereby improving the convenience of assembly. The prefabrication method can be milling, tapping, grinding, etc., which is not limited herein.

[0066] In addition, the present application also provides an assembly method for a planetary roller screw structure. The nut sleeve 1, the roller 200, and the screw rod 3 are provided. The inner side of the nut sleeve 1 is prefabricated with an internal thread portion 101 and a ring gear 4. The cage 5 is provided. The cage 5 is placed into the nut sleeve 1. When the roller 200 is correspondingly installed into the cage 5, the roller 200 is threadedly engaged with the internal thread portion 101, and the roller 200 is meshed with the ring gear 4, and then the screw rod 3 is assembled into the nut sleeve 1 and threadedly engaged with the roller 200.

[0067] At the position between the internal thread portion 101 and the ring gear 4, an avoidance area S is also pre-milled. When the cage 5 is placed into the nut sleeve 1 along the axial direction of the nut sleeve 1, the cage 5 is fixed at the depth position of the avoidance area S through a tooling.

[0068] Among them, the nut sleeve 1 is formed by the above processing method. During assembly, since the ring gear 4 and the nut sleeve 1 are integral parts, it is not necessary to assemble the ring gear 4 as in the related art, which improves the convenience of assembly.

[0069] The above embodiments are only used to illustrate the present application and do not limit the technical solutions described in the present application. The understanding of this specification should be based on those skilled in the art. For example, the directional descriptions such as "front", "rear", "left", "right", "up", and "down" are only used to describe the relationship between objects and are not substantive limitations. "Multiple" means at least two or more.

[0070] Although this specification has described the present application in detail with reference to the above embodiments, those of ordinary skill in the art should understand that those skilled in the art can still modify or equivalently replace the present application, and all technical solutions and their improvements that do not depart from the spirit and scope of the present application should be covered within the scope of the claims of the present application.

Claims

1. A planetary roller screw structure, characterized in that, It includes a nut sleeve (1), a roller set (2) and a lead screw (3). The roller set (2) includes a plurality of rollers (200). The roller (200) includes a first section (201) and a second section (202). The nut sleeve (1) includes an internal thread portion (101). The lead screw (3) is in threaded fit with the first section (201), and the first section (201) is in threaded fit with the internal thread portion (101). The planetary roller lead screw structure includes a gear ring (4). The gear ring (4) is in meshing fit with the second section (202), and the gear ring (4) and the nut sleeve (1) are integral parts.

2. The planetary roller screw structure according to claim 1, characterized in that, The gear ring (4) extends from the inner wall of the nut sleeve (1) towards the center of the nut sleeve (1). The gear ring (4) includes an internal tooth portion (401). The second section (202) includes an external tooth portion. The internal tooth portion (401) is in meshing fit with the external tooth portion. The planetary roller lead screw structure includes a cage (5). The cage (5) is connected to the roller (200). The maximum diameter of the cage (5) is smaller than the minimum diameter of the tooth portion (401). On the projection plane perpendicular to the axial direction of the nut sleeve (1), the projection of the tooth portion (401) coincides with the projection of the internal thread portion (101).

3. The planetary roller screw structure according to claim 2, wherein, In the axial direction of the nut sleeve (1), there is a relief zone (S) between the tooth portion (401) and the internal thread portion (101). On the projection plane along the radial direction of the nut sleeve (1), at least part of the projection of the cage (5) falls into the relief zone (S).

4. The planetary roller screw structure according to claim 3, characterized in that, The roller (200) includes a transition section (203). The first section (201) is connected to the transition section (203), and the second section (202) is connected to the transition section (203). The cage (5) is connected to the transition section (203). On the projection plane along the radial direction of the nut sleeve (1), the transition section (203) falls into the relief zone (S).

5. The planetary roller screw structure according to claim 2 or 4, characterized in that, In the circumferential direction of the cage (5), the rollers (200) are evenly spaced. The roller set (2) is in a circular ring shape. The maximum diameter of the cage (5) is smaller than the maximum diameter of the roller set (2).

6. The planetary roller screw structure according to claim 2 or 4, characterized in that, There are two gear rings (4). In the axial direction of the nut sleeve (1), the two gear rings (4) are respectively located at both ends of the internal thread portion (101).

7. A processing method for a planetary roller screw structure, characterized in that, A tubular workpiece is provided. An internal thread portion (101) that can be in threaded fit with the roller (200) is prefabricated on the inner side of the tubular workpiece. In the axial direction of the tubular workpiece, a gear ring (4) that can be in meshing fit with the roller (200) is prefabricated on the inner side of the tubular workpiece. The tubular workpiece is processed to form a nut sleeve (1).

8. The processing method of the planetary roller screw structure according to claim 7, characterized in that, When milling one of the internal thread portion (101) or the gear ring (4) on the inner wall of the cylindrical workpiece, a spacing for the avoidance area (S) is left along the axial direction of the cylindrical workpiece. After milling the space of the avoidance area (S) on the inner wall of the cylindrical workpiece, the other of the internal thread portion (101) or the gear ring (4) is milled on the inner wall of the cylindrical workpiece.

9. An assembly method for a planetary roller screw structure, characterized in that, A nut sleeve (1), rollers (200) and a lead screw (3) are provided. The inner side of the nut sleeve (1) is prefabricated with an internal thread portion (101) and a gear ring (4). A cage (5) is provided. When the cage (5) is placed into the nut sleeve (1) and the rollers (200) are correspondingly installed on the cage (5), the rollers (200) are threadedly engaged with the internal thread portion (101) and meshed with the gear ring (4). Then, the lead screw (3) is assembled into the nut sleeve (1) and threadedly engaged with the rollers (200).

10. The assembling method of the planetary roller screw structure according to claim 9, characterized in that, An avoidance area (S) is also pre-milled at a position between the internal thread portion (101) and the gear ring (4). When the cage (5) is placed into the nut sleeve (1) along the axial direction of the nut sleeve (1), the cage (5) is fixed at the depth position of the avoidance area (S) by a tooling.

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