Differential planetary roller screw assembly tooling

Abstract

This utility model discloses a differential planetary roller screw assembly fixture. A boss is provided on the front end face of the disc seat, with the front end face of the boss serving as the contact surface. Several stepped grooves, evenly distributed on the same circumferential surface, are formed on the contact surface. These stepped grooves extend axially forward, and their front ends are located on the disc seat. The openings of the stepped grooves are radially outward. By setting six evenly distributed stepped grooves on the contact surface of the boss on the disc seat, a circumferential rigid constraint can be formed on the rollers, controlling the circumferential distribution error of the rollers within ±0.5°. The three-stage design of the stepped grooves precisely matches the first, second, and third-stage steps of the rollers, with a radial positioning error ≤0.02mm, ensuring that the initial meshing position of the rollers and nut teeth meets the design requirements. The multi-stage surface contact between the stepped grooves and the rollers is a surface contact, reducing the force per unit area by more than 60%. Furthermore, the U-shaped groove opening uses a rounded corner transition to avoid scratches on the roller surface.

Description

Technical Field

[0001] This utility model relates to the assembly of differential planetary roller screws, and in particular to the assembly tooling for differential planetary roller screws. Background Technology

[0002] Differential planetary roller screws, as a high-precision, high-load-bearing transmission mechanism, are widely used in high-end equipment fields such as aerospace, CNC machine tools, and robotics. Their core structure consists of a screw, a nut, and several evenly distributed rollers. The rollers have specially machined tooth profiles that precisely mesh with the tooth grooves of the screw and nut. Furthermore, the positional accuracy of the rollers in the circumferential direction directly affects the transmission efficiency and service life.

[0003] Currently, the assembly of differential planetary roller screws faces the following technical challenges: Roller positioning is difficult: the rollers need to be evenly distributed along the inner circumference of the nut (usually 6-8). Traditional manual assembly relies on the operator's experience to adjust the position, which easily leads to uneven circumferential spacing (error can reach ±5° or more), resulting in stress concentration during transmission and reducing the equipment life.

[0004] Low tooth meshing accuracy: The tooth profiles of the roller, nut, and lead screw need to be strictly aligned. During manual assembly, it is difficult to ensure that the tooth surfaces are completely in contact, which can easily lead to incomplete connection or jamming, resulting in transmission clearance exceeding the tolerance (usually more than 0.05mm).

[0005] Low assembly efficiency: The assembly of a single set of lead screws requires repeated adjustment of the roller position, trial assembly of the retainer and retaining ring. A skilled worker can spend more than 30 minutes on a single assembly, and the pass rate is only 70%-80%.

[0006] Easy to cause assembly damage: During manual adjustment, the hard friction between the roller and the inner wall of the nut can easily cause scratches on the tooth surface, especially for high-precision tooth profiles with surface hardening (hardness HRC58-62). Even minor damage can lead to increased transmission noise or decreased precision.

[0007] Existing assembly tools are mostly general-purpose fixtures, which cannot be matched with the stepped structure of differential rollers, making it difficult to simultaneously meet the requirements for positioning accuracy and tooth profile protection. Therefore, the development of a specialized tooling that adapts to the stepped structure of rollers and enables precise positioning and efficient assembly has become an urgent need in the industry. Utility Model Content

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a differential planetary roller screw assembly fixture.

[0009] The purpose of this utility model is achieved through the following technical solution: a differential planetary roller screw assembly fixture, including a disc seat, a boss is provided on the front end face of the disc seat, the front end face of the boss is a contact surface, and a number of stepped grooves evenly distributed on the same circumferential surface are opened on the contact surface. The stepped grooves extend forward along the axial direction, and the front end face of the stepped grooves is located on the disc seat. The groove openings of the stepped grooves are radially outward.

[0010] Optional, there are six stepped slots.

[0011] Optionally, the stepped grooves are arranged from back to front as a first-level stepped groove, a second-level stepped groove, and a third-level stepped groove. In the radial direction, the depth of the first-level stepped groove is greater than the depth of the second-level stepped groove, and the depth of the second-level stepped groove is greater than the depth of the third-level stepped groove.

[0012] Optionally, on the axial projection plane, the first-level stepped groove, the second-level stepped groove, and the third-level stepped groove are all U-shaped grooves.

[0013] Optionally, a central hole is provided at the center of the contact surface, which extends axially forward and passes through the disk seat.

[0014] This utility model has the following advantages: 1. By setting six evenly distributed stepped grooves (with adjacent angles of 60°) on the contact surface of the disc seat boss, a circumferential rigid constraint can be formed on the roller, controlling the circumferential distribution error of the roller within ±0.5°. The three-stage design of the stepped groove precisely matches the first, second, and third stage steps of the roller, with a radial positioning error ≤0.02mm, ensuring that the initial meshing position of the roller and the nut tooth groove meets the design requirements; 2. The U-shaped groove design of the stepped groove (axial projection) can guide the roller to be smoothly inserted and automatically centered. Combined with the axial clamping action of the mandrel, the roller tooth surface and the nut tooth groove are completely fitted (fitting degree ≥95%), effectively eliminating the phenomenon of loose connection. After assembly, the transmission clearance can be controlled at 0.01-0.03mm, which is better than the 0.05mm standard of traditional manual assembly. 3. The tooling allows for one-time positioning of the rollers, eliminating repeated adjustments and reducing the assembly time for a single lead screw from 30 minutes to less than 10 minutes, while increasing the assembly qualification rate to over 99%. Simultaneously, the installation of the cage and the elastic retaining ring for the hole can be completed directly while the tooling is positioned, reducing process connection time. 4. The multi-step surface contact between the stepped groove and the roller is a surface contact rather than a line contact, which reduces the force per unit area by more than 60%, and the U-shaped groove uses rounded corners to avoid scratches on the roller surface. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the present invention. Figure 1 ; Figure 2 This is a schematic diagram of the structure of the present invention. Figure 2 ; Figure 3 A schematic diagram showing the tooling and ball bearings installed inside the nut; Figure 4 This is a schematic diagram of a mandrel installed inside a nut. Figure 5 A schematic diagram showing the installation of the retainer and hole on the rear side of the nut using an elastic retaining ring; Figure 6 A schematic diagram of the mandrel ejection fixture; Figure 7 A schematic diagram showing the installation of the retainer and hole on the front side of the nut using an elastic retaining ring; In the figure, 1-disc seat, 2-boss, 3-abutting surface, 4-stepped groove, 41-first-level groove, 42-second-level groove, 43-third-level groove, 5-lead screw, 6-nut, 7-roller, 8-cage, 9-elastic retaining ring for hole. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can typically be arranged and designed in various different configurations.

[0017] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0018] It should be noted that, where there is no conflict, the embodiments and features in the embodiments of this utility model can be combined with each other.

[0019] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0020] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this utility model is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0021] In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0022] like Figure 1 and Figure 2 As shown, the differential planetary roller screw assembly fixture includes a disc seat 1. A boss 2 is provided on the front end face of the disc seat 1. The front end face of the boss 2 is a contact surface 3. Several stepped grooves 4 are evenly distributed on the same circumferential surface on the contact surface 3. The stepped grooves 4 extend forward axially, and the front end face of the stepped grooves 4 is located on the disc seat 1. The groove openings of the stepped grooves 4 are radially outward. In this embodiment, there are six stepped grooves 4. The six stepped grooves 4 are evenly distributed on the same circumferential surface, so the included angle between two adjacent stepped grooves 4 is 60°. Furthermore, the stepped grooves 4 are arranged sequentially from back to front as a first-level stepped groove 414, a second-level stepped groove 42, and a third-level stepped groove 43. Upward, the depth of the first-level stepped groove 414 is greater than the depth of the second-level stepped groove 42, and the depth of the second-level stepped groove 42 is greater than the depth of the third-level stepped groove 43. In this embodiment, the roller 7 has a symmetrical structure, with a first-level stepped column, a second-level stepped column, and a third-level stepped column arranged sequentially from the middle to both sides. During installation, the first-level stepped column is placed on the first-level stepped groove 414, the second-level stepped column is placed on the second-level stepped groove 42, and the third-level stepped column is placed on the third-level stepped groove 43. Furthermore, on the axial projection plane, the first-level stepped groove 414, the second-level stepped groove 42, and the third-level stepped groove 43 are all U-shaped grooves, which facilitates the easy insertion of the roller 7 into the stepped groove 4.

[0023] In this embodiment, a central hole is provided in the center of the contact surface 3. The central hole extends axially forward and penetrates the disc seat 1. The central hole has the function of venting. When the mandrel 10 abuts against the contact surface 3 during installation, the gas in the nut 6 is discharged from the central hole, thereby avoiding air resistance and allowing the mandrel 10 and the contact surface 3 to fit smoothly.

[0024] The working process of this utility model is as follows: Figures 3-7 As shown, the tooling is inserted into the front end of the nut 6, and the six rollers 7 are sequentially inserted into the nut 6, such that the first-stage stepped roller at the front end of the ball is supported by the first-stage stepped groove 41, the second-stage stepped roller is supported by the second-stage stepped groove 42, and the third-stage stepped roller is supported by the third-stage stepped groove 43. Then, the mandrel 10 is inserted into the nut 6 from back to front, so that the front end face of the mandrel 10 contacts the contact surface 3. At this time, the mandrel 10 presses against the first-stage stepped roller at the rear end of the ball, so that the roller 7 is supported by the mandrel 10, and the tooth profile of the roller 7 meshes with the tooth profile of the nut 6. However, the front end of the mandrel 10 is still in the corresponding stepped groove 4. The stepped groove 4 can restrict the position of the ball in the circumferential direction, thereby ensuring that the position of the six rollers 7 in the circumferential direction is fixed. Then, the cage 8 is inserted into the rear end of the nut 6. Inside the cavity, the three-stage stepped column is installed in the mounting hole of the cage 8, and the stepped surface between the three-stage stepped column and the second-stage stepped column abuts against the front end face of the cage 8. Finally, the elastic retaining ring 9 is used to hold the rear end cavity of the nut 6, thereby abutting against the rear end face of the cage 8. The rear end cavity of the nut 6 is also provided to abut against the front end face of the cage 8, thereby preventing the cage 8 from moving axially. Then, the mandrel 10 is pushed forward, causing the disc seat 1 to exit the cavity of the nut 6. Then, the tooling is removed, and then the cage 8 and the elastic retaining ring 9 are installed in sequence in the front end cavity of the nut 6. Preferably, the elastic retaining ring 9 is a retaining spring, thereby completing the installation of the roller 7. Finally, the mandrel 10 is removed, and the lead screw 5 is installed into the nut 6, thereby completing the assembly of the differential planetary roller 7 lead screw 5.

[0025] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A differential planetary roller screw assembly tooling fixture, characterized by: The device includes a disc base, a boss is provided on the front end face of the disc base, the front end face of the boss is a contact surface, and a plurality of stepped grooves are evenly distributed on the same circumferential surface on the contact surface. The stepped grooves extend forward along the axial direction, and the front end face of the stepped grooves is located on the disc base. The groove openings of the plurality of stepped grooves are radially outward.

2. The differential planetary roller screw assembly tooling of claim 1, wherein: There are six stepped grooves.

3. The differential planetary roller screw assembly tooling of claim 1, wherein: The stepped grooves are arranged from back to front as a first-level stepped groove, a second-level stepped groove, and a third-level stepped groove. In the radial direction, the depth of the first-level stepped groove is greater than the depth of the second-level stepped groove, and the depth of the second-level stepped groove is greater than the depth of the third-level stepped groove.

4. The differential planetary roller screw assembly tool of claim 3, wherein: On the axial projection plane, the first-level stepped groove, the second-level stepped groove, and the third-level stepped groove are all U-shaped grooves.

5. The differential planetary roller screw assembly tooling of claim 1, wherein: A central hole is provided at the center of the contact surface, and the central hole extends axially forward and penetrates the disk seat.

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