Planetary roller screw pair

Abstract

The utility model discloses a planetary roller lead screw pair, and relates to the technical field of transmission devices, the planetary roller lead screw pair comprises a nut, a lead screw, a plurality of planetary rollers and two retainers, the lead screw is arranged in the nut in a penetrating mode, and the axis of the lead screw coincides with the axis of the nut; the multiple planetary rollers are evenly installed on the outer circumference of the lead screw in a surrounding mode, each planetary roller comprises a first threaded section, threaded sections coaxially connected to the two ends of the first threaded section and supporting columns coaxially connected to the two ends of the threaded sections, and the threaded sections of the planetary rollers are meshed with external threads of the lead screw and internal threads of the nut at the same time; the two retainers are located on the two sides in the nut respectively, each retainer is provided with a plurality of positioning holes evenly distributed in the circumferential direction, and the end, away from the threaded section, of each supporting column is correspondingly supported on the retainer on the corresponding side in a penetrating and inserting mode. The transmission device can be easily connected with application occasions, and is high in transmission rigidity, stable in transmission, high in reliability, long in service life and the like.

Description

Technical Field

[0001] The utility model relates to the technical field of transmission devices, in particular to a planetary roller screw pair. Background Art

[0002] Planetary roller screw pair is a mechanical transmission device that can convert rotational motion and linear motion into each other. It is composed of screw, nut, rolling element, planet carrier, inner gear ring, etc. The rolling element of planetary roller screw pair is planetary roller. Compared with the commonly used ball screw pair, planetary roller screw pair has the transmission characteristics of multi-point, multi-pair and multi-body, which determines its advantages of large thrust, high precision, high rigidity, long life, good dynamic performance, easy installation and maintenance, etc.

[0003] At present, under the action of large load, the traditional planetary roller screw pair will generate large contact stress and contact deformation at the threaded meshing of the screw and roller, and the roller and nut, because the conventional nut and the inner teeth of the nut are two independent parts. Therefore, a certain axial transmission clearance will be generated on the opposite side of the contact point of the thread raceway. Especially at starting, stopping and especially reversing time, the axial transmission clearance of the planetary roller screw pair will lead to adverse phenomena such as creeping and impact, thereby reducing the accuracy, transmission stiffness and service life of the roller screw pair.

[0004] In addition, the separate assembly structure of the nut and the inner teeth of the nut requires a certain radial dimension of the nut when the inner gear ring is installed and fixed to the inner wall of the nut (such as fastening with a pin), resulting in a non-compact structure and low space utilization. Utility Model Content

[0005] The main purpose of the utility model is to provide a planetary roller screw pair, aiming to solve the technical problems of the existing planetary roller screw pair that easily lead to unstable transmission, non-compact structure and low space utilization.

[0006] In order to achieve the above-mentioned purpose, the utility model proposes a planetary roller screw pair, comprising:

[0007] Nuts;

[0008] A lead screw is inserted into the nut, and the axis of the lead screw coincides with the axis of the nut;

[0009] A plurality of planetary rollers, the plurality of planetary rollers are evenly mounted around the outer circumference of the lead screw, each of the planetary rollers comprises a first thread segment, a thread segment coaxially connected to both ends of the first thread segment, and a support column coaxially connected to both ends of the thread segment, and the thread segment of the planetary roller is meshed with the external thread of the lead screw and the internal thread of the nut at the same time;

[0010] Two retaining frames are respectively located on both sides of the nut, each retaining frame is provided with a plurality of positioning holes evenly distributed in the circumferential direction, and one end of each support column away from the threaded section is correspondingly inserted and supported on the retaining frame on the corresponding side.

[0011] Optionally, the nut includes a nut seat, two nut internal teeth integrally connected to the inner wall of the nut seat in a circumferential direction, and a nut flange integrally connected to the outer circumferential direction of the nut seat; the two nut internal teeth are symmetrically located on both sides of the nut seat, the nut internal teeth are respectively engaged with the corresponding threaded sections, and the nut internal teeth have the same number of teeth and module as the threaded sections.

[0012] Optionally, a wire retaining ring is provided between the nut seat and the retaining frame, and annular grooves in the axial direction are respectively opened on the inner walls on both sides of the nut seat, and the wire retaining ring is suitable for being accommodated in the annular groove to axially position the retaining frame and install it in the nut seat.

[0013] Optionally, the screw includes a screw body, a screw thread integrally connected to the screw body, a screw spline connected to one end of the screw body, and a screw pin hole radially penetrated through the screw body, the screw thread is meshed with the threaded section of the planetary roller, and the screw thread has the same number of teeth and module as the threaded section, the screw spline is suitable for connecting to an external driving mechanism, and the screw pin hole is suitable for inserting a pin shaft.

[0014] Optionally, the thread profiles of the lead screw thread and the inner teeth of the nut are both triangular, and the thread profile of the thread section is a convex arc.

[0015] Optionally, a single-start thread is provided on the outer side of the threaded section, and multiple-start threads are provided on the outer side of the lead screw thread and the inner side of the inner teeth of the nut, and the number of thread starts is the same.

[0016] Optionally, the threaded section and the internal teeth of the nut have the same helix angle.

[0017] Optionally, the diameter of the first thread segment is smaller than the minor diameter of the external thread of the thread section.

[0018] Optionally, the number of the planetary rollers is nine.

[0019] Optionally, the length of the first thread segment is greater than 1 thread pitch.

[0020] Compared with the prior art, the beneficial effects of the utility model are:

[0021] 1. In the technical solution of the utility model, the planetary roller screw pair is composed of a screw, a plurality of planetary rollers, a nut and two retaining frames. The screw is inserted into the nut, and the axis of the screw coincides with the axis of the nut, so that power is input through the screw, one end of the screw is connected to the motor, and the output of the motion is connected to the actuator through the nut; a plurality of planetary rollers are evenly mounted around the outer circumference of the screw, the threaded sections of the planetary rollers are coaxially connected to the two ends of the first threaded section, the support column is coaxially connected to the two ends of the threaded section, and the threaded sections of the planetary rollers are meshed with the external thread of the screw and the internal thread of the nut at the same time, thereby reducing the contact stress and contact deformation generated at the meshing point; the two retaining frames are respectively located on both sides of the nut, each retaining frame is provided with a plurality of positioning holes evenly distributed in the circumferential direction, and one end of each support column away from the threaded section is correspondingly inserted and supported on the retaining frame on the corresponding side, ensuring that the plurality of planetary rollers are evenly distributed in the circumferential direction of the screw, making the assembly more stable and reducing the phase error. The above structure can simultaneously eliminate the bilateral axial transmission clearance between the roller and the screw, and between the roller and the nut thread, making the preload force in the planetary roller screw pair symmetrical and uniform, eliminating adverse phenomena such as reverse creep and impact, thereby improving the axial transmission stiffness, reverse transmission accuracy and service life of the planetary roller screw pair. The structure is simple and there is no need to increase the nut structure and the complexity of production. It has smooth transmission, compact structure and high space utilization.

[0022] 2. The integrated nut structure avoids the assembly phase error of the inner gear ring in the split structure, as well as the assembly deformation problem of the inner gear ring when the inner gear ring is radially fixed, which can achieve higher assembly accuracy, thereby improving the overall transmission accuracy, transmission efficiency and service life of the screw pair. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0024] Figure 1 A schematic diagram of the three-dimensional structure of a planetary roller screw pair provided in an embodiment of the utility model;

[0025] Figure 2 This is a schematic diagram of the main structure of the planetary roller screw pair in the embodiment of the utility model;

[0026] Figure 3 for Figure 2 Schematic diagram of the cross-sectional structure in the middle DD direction;

[0027] Figure 4It is a side view structural diagram of a planetary roller screw pair in an embodiment of the utility model;

[0028] Figure 5 It is a schematic cross-sectional view of the planetary roller screw pair in the embodiment of the utility model;

[0029] Figure 6 This is a schematic diagram of the structure of the lead screw in the embodiment of the utility model;

[0030] Figure 7 This is a schematic diagram of the structure of the planetary rollers, the cage and the wire retaining ring in the embodiment of the utility model;

[0031] Figure 8 It is a schematic diagram of the cross-sectional structure of the nut in the embodiment of the utility model.

[0032] Description of Figure Numbers:

[0033] 1-screw; 11-screw body; 12-screw thread; 13-screw spline; 14-screw pin hole;

[0034] 2-planetary roller; 21-first thread segment; 22-thread segment; 23-support column;

[0035] 3-nut; 31-nut seat; 311-annular groove; 32-nut inner teeth; 33-nut flange;

[0036] 4-cage; 41-first cage; 42-second cage; 43-positioning hole;

[0037] 5-Wire retaining ring. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0039] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0040] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the utility model, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the utility model.

[0041] At present, the existing standard planetary roller screw consists of four major components: screw, roller, nut and inner gear ring. The two inner gear rings are independent parts of the nut and need to be assembled into the inner holes of the corresponding nuts at the same phase angle, which requires a very high assembly accuracy of the inner gear rings; if there is a slight deviation in the assembly, it will directly affect the transmission performance, and even cause jamming, damaging the thread teeth and tooth structure.

[0042] On the one hand, due to space limitations, the outer circle of the inner gear ring cannot be made very large, so the inner gear ring parts are often thin, which greatly increases the difficulty of gear ring processing and easily causes gear ring deformation.

[0043] On the other hand, the internal gear ring is often fixed by means of pins. In the process of drilling pin holes and pressing pins, there is also the risk of damaging parts and movement of the internal gear ring.

[0044] Finally, due to the need to fix the inner gear ring, many threaded holes and pin holes for assembly need to be drilled on the corresponding outer cylindrical surface of the nut, which is more complicated in process.

[0045] To solve the above technical problems, please refer to Figure 1-8 As shown, the utility model provides a planetary roller screw pair, which includes a screw 1, a plurality of planetary rollers 2, a nut 3 and two retaining frames 4, wherein:

[0046] The lead screw 1 is passed through the nut 3, and the axis of the lead screw 1 coincides with the axis of the nut 3; a plurality of planetary rollers 2 are evenly mounted around the outer circumference of the lead screw 1, each planetary roller 2 comprises a first threaded section 21, a threaded section 22 and a support column 23, the threaded section 22 is coaxially connected at both ends of the first threaded section 21, the support column 23 is coaxially connected at both ends of the threaded section 22, and the threaded section 22 of the planetary roller 2 is simultaneously meshed with the external thread of the lead screw 1 and the internal thread of the nut 3; two retaining frames 4 are respectively located on both sides of the nut 3, each retaining frame 4 is provided with a plurality of positioning holes 43 evenly distributed in the circumferential direction, and one end of each support column 23 away from the threaded section 22 is correspondingly inserted and supported on the retaining frame 4 on the corresponding side.

[0047] like Figure 1-4 The planetary roller screw pair shown in the figure is composed of a screw 1, a plurality of planetary rollers 2, a nut 3 and two retaining frames 4. The screw 1 and the two retaining frames 4 in this embodiment are attached Figure 3 The first retainer 41 and the second retainer 42 are respectively installed at the two ends of the nut 3, and are used to support the support column 23 of the planetary roller 2 to ensure that the nut 3 and the threaded section 22 of the planetary roller 2 are stably engaged. In addition, the threaded section 22 of the planetary roller 2 is engaged with the internal teeth at both ends of the nut 3, and the threaded section 22 of the planetary roller 2 is engaged with the threaded part of the nut 3 and the screw 1 at the same time. The power is input through the screw 1, one end of the screw 1 is connected to the motor, and the output of the motion is connected to the actuator through the nut 3. The motor drives the screw 1 to rotate, and drives the planetary roller 2 to rotate in the opposite direction through the friction torque. At the same time, the planetary roller 2 revolves in the same direction, thereby driving the nut 3 to move linearly. Since the nut 3 is circumferentially free, the nut 3 also has rotational motion while moving linearly.

[0048] The planetary roller screw pair adopting the above structure converts rotational motion into linear motion while eliminating the bilateral axial transmission clearance between the roller and the screw, and between the roller and the nut thread, so that the preload force in the planetary roller screw pair is symmetrical and uniform, eliminating adverse phenomena such as reverse creep and impact, thereby improving the axial transmission stiffness, reverse transmission accuracy and service life of the planetary roller screw pair. The structure is simple, and there is no need to increase the nut structure and the complexity of production. It has smooth transmission, compact structure and high space utilization.

[0049] Furthermore, the nut 3 includes a nut seat 31, two nut internal teeth 32 and a nut flange 33. The two nut internal teeth 32 are integrally connected in the circumferential direction of the inner wall of the nut seat 31, and the nut flange 33 is integrally connected in the outer circumferential direction of the nut seat 31. The two nut internal teeth 32 are symmetrically located on both sides of the nut seat 31, and the nut internal teeth 32 are respectively meshed with the corresponding threaded sections 22, and the nut internal teeth 32 have the same number of teeth and module as the threaded sections 22.

[0050] In addition, a threaded section meshing with the first threaded section 21 of the planetary roller 2 is also provided inside the nut seat 31 to further ensure the accuracy of the meshing transmission.

[0051] See also Figure 5 , 8As shown, in the specific embodiment of the utility model, compared with the traditional planetary roller screw pair structure, the conventional nut 3 and the conventional nut inner teeth 32 are two independent parts. In this embodiment, they are combined into an integral part (nut 3) including the nut inner teeth 32. The nut 3 is composed of an integrally connected nut seat 31, two nut inner teeth 32 and a nut flange 33. The nut 3 and the inner gear ring are designed as an integrated structure, so that the outer diameter of the nut 3 can be designed to be smaller to adapt to the use environment with a smaller installation space; the overall rigidity of the planetary roller screw pair is significantly improved, thereby improving the overall performance; effectively avoiding the risk of plastic deformation of the inner gear ring of the nut inner teeth 32 during the processing; and effectively avoiding the assembly phase error and assembly deformation of the inner gear ring in the independent split structure, thereby obtaining higher assembly accuracy, thereby improving the overall transmission accuracy, transmission efficiency and service life of the screw pair.

[0052] Furthermore, a wire retaining ring 5 is provided between the nut seat 31 and the retaining frame 4, and an annular groove 311 in the axial direction is respectively opened on the inner walls on both sides of the nut seat 31. The wire retaining ring 5 is suitable for being accommodated in the annular groove 311 to axially position the retaining frame 4 in the nut seat 31.

[0053] For more details, see Figure 3 , 5 As shown in Figures 7 and 8, in a specific embodiment of the utility model, two retaining frames 4 are respectively installed at both ends of the nut 3, and each retaining frame 4 is connected to the support columns 23 of multiple planetary rollers 2 to ensure that the multiple planetary rollers 2 are evenly distributed in the circumferential direction of the screw 1. The two retaining frames 4 are axially positioned in the nut 3 by two wire retaining rings 5.

[0054] Furthermore, the screw 1 includes a screw body 11, a screw thread 12, a screw spline 13 and a screw pin hole 14. The screw thread 12 is integrally connected to the screw body 11, the screw spline 13 is connected to one end of the screw body 11, and the screw pin hole 14 is radially penetrated on the screw body 11. The screw thread 12 is meshed with the threaded section 22 of the planetary roller 2, and the screw thread 12 and the threaded section 22 have the same number of teeth and module. The screw spline 13 is suitable for connecting to an external driving mechanism, and the screw pin hole 14 is suitable for inserting a pin shaft.

[0055] See also Figure 1 , 5 As shown in Figures 6, in a specific embodiment of the utility model, the lead screw 1 is composed of a lead screw body 11, a lead screw thread 12, a lead screw spline 13 and a lead screw pin hole 14. One end of the lead screw 1 is provided with a lead screw spline 13 for connecting with an external driving mechanism, and the outer cylindrical surface of the lead screw 1 is provided with a lead screw pin hole 14 for installing a pin to connect with an external structure, so as to lock the lead screw and prevent the lead screw from rotating under load when it stops working.

[0056] Furthermore, the thread profiles of the lead screw thread 12 and the nut internal teeth 32 are both triangular, and the thread profile of the thread section 22 is a convex arc.

[0057] For details, please refer to Figure 5 As shown, in the specific embodiment of the utility model, the thread profiles of the screw thread 12 and the nut internal teeth 32 are both triangular, and the axial section of the thread profile is a right-angled triangle, which is simpler and more intuitive among the existing truncated shapes, and is easy to turn; the normal section shape of the thread section 22 is an arc, the center of the arc is located on the roller axis, and is an outward convex arc. The actual mean diameter of the thread of the screw 1 can be reduced, while meeting the conditions of strong load-bearing capacity and a single degree of freedom.

[0058] Furthermore, a single-start thread is provided on the outer side of the threaded section 22 , and multiple-start threads are provided on the outer side of the lead screw thread 12 and the inner side of the nut internal teeth 32 , and the number of thread starts is the same.

[0059] At present, the three-element threads in the existing planetary roller screw pair are usually: the number of starts of the nut internal teeth 32 of the nut 3 is the same as the number of starts of the screw thread 12 of the screw 1; the planetary roller 2 is a single-start thread; the thread section 22 of the planetary roller 2 and the thread lead angle of the nut internal teeth 32 of the nut 3 are the same. Figure 7 As shown, in the specific embodiment of the utility model, as the preferred embodiment of this embodiment, the outer side of the threaded section 22 is provided with a single-start thread, the outer side of the screw thread 12 and the inner side of the nut internal teeth 32 are provided with multi-start threads, and the number of thread heads is the same, which improves the meshing quality and reduces the difficulty of the processing technology.

[0060] Furthermore, the helix angles of the threaded section 22 and the nut internal teeth 32 are the same.

[0061] Furthermore, in a specific solution of the present invention, the diameter of the first thread segment 21 is smaller than the minor diameter of the external thread of the thread segment 22 .

[0062] Preferably, the number of the planetary rollers 2 is nine, and the length of the first thread segment 21 of the planetary roller 2 is greater than 1 pitch.

[0063] The above description is only a preferred embodiment of the utility model, and does not limit the patent scope of the utility model. All equivalent structural changes made by using the contents of the utility model specification and drawings under the utility model concept, or directly / indirectly used in other related technical fields are included in the patent protection scope of the utility model.

Claims

1. A planetary roller screw pair, characterized in that: include: Nut (3); A lead screw (1) is inserted into the nut (3), and the axis of the lead screw (1) coincides with the axis of the nut (3); A plurality of planetary rollers (2), wherein the plurality of planetary rollers (2) are evenly mounted around the outer circumference of the lead screw (1), each of the planetary rollers (2) comprises a first threaded section (21), a threaded section (22) coaxially connected to both ends of the first threaded section (21), and a support column (23) coaxially connected to both ends of the threaded section (22), and the threaded section (22) of the planetary roller (2) is simultaneously meshed with the external thread of the lead screw (1) and the internal thread of the nut (3); Two retaining frames (4) are respectively located on two sides of the nut (3), each retaining frame (4) is provided with a plurality of positioning holes (43) evenly distributed in the circumferential direction, and one end of each support column (23) away from the threaded section (22) is correspondingly inserted and supported on the retaining frame (4) on the corresponding side.

2. The planetary roller screw pair according to claim 1, characterized in that: The nut (3) comprises a nut seat (31), two nut internal teeth (32) integrally connected to the inner wall of the nut seat (31) in a circumferential direction, and a nut flange (33) integrally connected to the outer circumferential direction of the nut seat (31); the two nut internal teeth (32) are symmetrically located on both sides of the nut seat (31), the nut internal teeth (32) are respectively meshed with the corresponding threaded sections (22), and the nut internal teeth (32) and the threaded sections (22) have the same number of teeth and module.

3. The planetary roller screw pair according to claim 2, characterized in that: A wire retaining ring (5) is also provided between the nut seat (31) and the retaining frame (4), and an annular groove (311) in the axial direction is respectively provided on the inner walls on both sides of the nut seat (31), and the wire retaining ring (5) is suitable for being accommodated in the annular groove (311) so as to axially position the retaining frame (4) and install it in the nut seat (31).

4. The planetary roller screw pair according to claim 2, characterized in that: The lead screw (1) comprises a lead screw body (11), a lead screw thread (12) integrally connected to the lead screw body (11), a lead screw spline (13) connected to one end of the lead screw body (11), and a lead screw pin hole (14) radially penetrated through the lead screw body (11); the lead screw thread (12) is meshed with a threaded section (22) of the planetary roller (2), and the lead screw thread (12) and the threaded section (22) have the same number of teeth and module; the lead screw spline (13) is suitable for connection with an external driving mechanism; and the lead screw pin hole (14) is suitable for inserting a pin shaft.

5. The planetary roller screw pair according to claim 4, characterized in that: The thread profiles of the lead screw thread (12) and the nut internal teeth (32) are both triangular, and the thread profile of the thread section (22) is a convex arc.

6. The planetary roller screw pair according to claim 4, characterized in that: The outer side of the threaded section (22) is provided with a single-start thread, and the outer side of the lead screw thread (12) and the inner side of the nut internal teeth (32) are both provided with multiple-start threads, and the number of thread starts is the same.

7. The planetary roller screw pair according to claim 2, characterized in that: The threaded section (22) and the nut internal teeth (32) have the same helix angle.

8. The planetary roller screw pair according to any one of claims 1 to 7, characterized in that: The diameter of the first thread segment (21) is smaller than the minor diameter of the external thread of the thread section (22).

9. The planetary roller screw pair according to any one of claims 1 to 7, characterized in that: The number of the planetary rollers (2) is nine.

10. The planetary roller screw pair according to claim 9, characterized in that: The length of the first thread segment (21) is greater than one thread pitch.

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