A reverse planetary roller screw structure

Abstract

The utility model relates to a kind of transmission device.A kind of reverse planetary roller screw structure, including screw rod and nut, roller is equipped between screw rod and nut, the roller thread section is equipped on the roller, spiral tooth structure is equipped on one side of roller thread section, the screw rod thread section is equipped on the screw rod, outer gear structure is equipped on one side of screw rod thread section;Helix structure on spiral tooth structure is matched with nut thread on the inner surface of nut, tooth structure on spiral tooth structure is matched with outer gear;The nut inner still is equipped with retainer, retainer is equipped with containing groove, roller is located in containing groove.The utility model provides a kind of reverse planetary roller screw structure, processing assembly is simple, transmission ratio is stable, axial displacement cannot be generated, and it will not occur deflection;Solve the technical problem of the existing technology, roller is prone to deflection, prone to broken tooth, leading to unstable structure, high processing cost.

Description

Technical Field

[0001] This utility model relates to a transmission device, and more particularly to a reverse planetary roller screw structure. Background Technology

[0002] A standard planetary roller screw consists of a screw, several rollers, a nut, an internal gear ring, a cage, and a snap ring. The rollers are installed inside the nut and engage with the threads of the screw and nut for power transmission.

[0003] Existing reverse planetary roller screws incorporate a double-gear structure, with gears also designed at both ends of the rollers. This structure ensures that the rollers and screw do not undergo axial displacement and prevents roller deflection. However, this structure has several problems: ① The gear structure, while preventing roller deflection, is subjected to eccentric loads, making it prone to tooth breakage; ② The double-gear structure requires specific phase angles between the gears at both ends, leading to high machining costs for the rollers and screw and increasing assembly difficulty.

[0004] When there is no gear transmission mechanism on the planetary roller screw, relative axial displacement will occur between the rollers and the nut. Therefore, the structure needs to be designed with a circulating mechanism or the helical lines on both the rollers and the nut need to be designed with annular grooves. When a circulating mechanism is designed, the rollers need to change direction, which not only causes energy loss and reduces transmission efficiency, but also easily generates noise. When the helical lines on both the rollers and the nut are designed with annular grooves, slippage is prone to occur, leading to unstable transmission ratios and affecting transmission efficiency. Summary of the Invention

[0005] This utility model provides a reverse planetary roller screw structure that is simple to process and assemble, has a stable transmission ratio, does not produce axial displacement, and does not deflect; it solves the technical problems of existing technologies, such as rollers being prone to deflection and tooth breakage, resulting in structural instability and high processing costs.

[0006] The above-mentioned technical problem of this utility model is solved by the following technical solution: a reverse planetary roller screw structure, including a screw and a nut, with a roller provided between the screw and the nut, the roller having a roller thread section, and a helical tooth structure on one side of the roller thread section; the screw having a screw thread section, and an external gear structure on one side of the screw thread section; the helical structure on the helical tooth structure engages with the nut thread on the inner surface of the nut, and the tooth structure on the helical tooth structure engages with the external gear; the nut also has a retainer, and the retainer has a receiving groove, with the roller located in the receiving groove.

[0007] A helical tooth structure is designed on one side of the roller, and a matching external gear structure is designed on the side of the screw that mates with the roller. The helical tooth structure of the roller has both thread and gear features; its thread only meshes with the thread on the nut, and its gear meshes with the external gear feature on the screw. Meanwhile, the cage is designed as a cage structure, allowing the roller to rotate freely within the receiving groove designed on the side of the cage. The gear structure on the roller only serves to ensure that the roller's rotation and revolution always operate in a fixed ratio, preventing relative axial displacement between the roller and the nut, thus reducing the requirements for the gears and greatly reducing the risk of tooth breakage. Furthermore, the designed cage structure of the cage effectively prevents the roller from deflecting due to the helix angle, thereby ensuring that the planetary roller screw mechanism can transmit power stably and efficiently.

[0008] Preferably, the transmission ratio between the helical teeth of the roller and the external gear is i. g The transmission ratio between the roller thread section and the lead screw thread section is i t i g =i t Transmission ratio i g The transmission ratio i of the threaded pair of rollers and nuts t This ensures that the rollers and nuts will not experience relative axial displacement.

[0009] Preferably, the cage is cylindrical with annular end faces. U-shaped grooves are formed on both end faces, corresponding to receiving grooves. These receiving grooves and the U-shaped grooves are coaxial, with both ends of the roller located within the U-shaped grooves. The openings of the U-shaped grooves face the nut. By using a small clearance fit between the U-shaped grooves on the end faces of the cage and the rollers, and a large clearance fit between the receiving grooves and the threaded ends of the rollers, the production and installation difficulties are reduced while ensuring the rollers do not deflect. This ensures that the gear meshing mechanism does not bear off-center loads and that the planetary roller screw mechanism maintains stable transmission. The outward-facing openings of the U-shaped grooves facilitate roller installation.

[0010] Preferably, the roller includes a threaded section in the middle and bosses at both ends. A helical tooth is provided between the boss at one end and the threaded section. The clearance between the boss and the U-shaped groove is 0.05±0.02mm, and the clearance between the threaded section and the receiving groove is greater than 0.2mm. The roller is designed as a four-section structure. Each end has a boss feature that mates with the U-shaped groove feature of the cage. One of the middle sections has both threaded and gear features; the thread only meshes with the thread on the lead screw, and the gear meshes with the internal gear ring feature on the nut. The other middle section only has a threaded feature, which meshes with the threaded features on both the lead screw and the nut for transmission.

[0011] Preferably, the clearance between the receiving groove and the roller is 0.05±0.02mm.

[0012] Preferably, the nut and lead screw have ≥2 thread starts, the roller has a single-start thread, and the helix angle of the roller and the lead screw are the same.

[0013] Therefore, the reverse planetary roller screw structure of this utility model has the following advantages: the roller has helical teeth on only one side, meshing with the external gear of the screw, effectively solving the problems of tooth breakage, difficult processing, and complex assembly in the double gear ring structure; at the same time, the cage-type cage design, through a small clearance fit, can effectively prevent the roller from deflecting due to the helix angle, thereby ensuring that the gear meshing mechanism does not bear the eccentric load and ensuring the stable transmission of the planetary roller screw mechanism; and the transmission ratio i g The transmission ratio i between roller and lead screw thread pair t This ensures that the rollers and nuts will not experience relative axial displacement. Attached Figure Description

[0014] Figure 1 This is an exploded view of a reverse planetary roller screw structure according to Example 1.

[0015] Figure 2 yes Figure 1 A three-dimensional view of the rollers inside.

[0016] Figure 3 yes Figure 1 A three-dimensional view of the internal cage.

[0017] Figure 4 This is an exploded view of Example 2. Detailed Implementation

[0018] The technical solution of the utility model will be further described in detail below through embodiments and in conjunction with the accompanying drawings.

[0019] Example 1:

[0020] like Figure 1 As shown, a reverse planetary roller screw structure includes a nut 1 and a screw 4 coaxially arranged. A plurality of rollers 3 are evenly distributed between the nut 1 and the screw 4, and the rollers 3 are mounted within a cage 2. A threaded section is formed on the inner wall of the nut 1. A screw threaded section 9 is formed on the screw 4, and an external gear structure 8 is formed on one side of the screw threaded section 9. The external gear structure 8 is integrally formed with the screw 4. The nut 1 and the screw 4 have at least two thread starts, the rollers 3 have single-start threads, and the helix angles of the rollers 3 and the screw 4 are the same.

[0021] like Figure 2As shown, roller 3 consists of four sections, including a large central roller thread section 7, which mates with the threads on both the nut and the lead screw. Both ends of the roller have bosses 6, the diameter of which is smaller than that of the roller thread section 7. A helical tooth section 5 is formed between one of the bosses 6 and the roller thread section 7. The gear structure of the helical teeth of the roller meshes with the external gear structure on the lead screw. The helical structure on the helical teeth only mates with the threads on the inner wall of the nut. The transmission ratio between the helical teeth and the external gear of the roller is i. g The transmission ratio between the roller thread section and the lead screw thread section is i t i g =i t .

[0022] like Figure 3 As shown, the cage 2 is cylindrical, with U-shaped grooves 10 formed on both end faces of the cage, the openings of the U-shaped grooves facing outwards. Receiving grooves 11 are formed on the cylindrical surface of the cage, the number of receiving grooves 11 being the same as the number of rollers. The U-shaped grooves 10 are located on both sides of the receiving grooves 11, and each U-shaped groove 10 and receiving groove 11 can accommodate one roller 3. The bosses 6 at both ends of the roller 3 are located within the U-shaped grooves 10, with a small clearance fit between the bosses 6 and the U-shaped grooves 10, the clearance being 0.05±0.02mm. The receiving grooves 11 and the threaded sections 7 of the rollers have a large clearance fit, the clearance being greater than 0.2mm.

[0023] When the nut rotates and the lead screw restricts its rotational movement, the nut drives the rollers to perform planetary motion through the helical feature that mates with the rollers. The lead screw also has a threaded feature that mates with the rollers, so the rotational motion of the nut is ultimately converted into the linear motion of the lead screw.

[0024] When the roller performs planetary motion, the helical teeth of the roller also mesh with the external gear on the lead screw. According to the principle of gear transmission, the transmission ratio between the helical teeth and the external gear is fixed. Therefore, the planetary motion of the roller can be guaranteed to operate in a fixed proportion, and this transmission ratio i g The transmission ratio i of the threaded pair of rollers and lead screws t This ensures that the rollers and lead screw will not experience relative axial displacement.

[0025] The small clearance between the U-groove and the bosses at both ends of the roller effectively prevents the roller from deflecting due to the helix angle, thus ensuring that the gear meshing mechanism does not bear off-center load and that the planetary roller screw mechanism can transmit stably.

[0026] Example 2:

[0027] like Figure 4As shown, unlike Embodiment 1, the roller 3 consists of two sections: a threaded section 7 and a helical tooth section 5. The threaded section 7 engages with the threads on both the lead screw and the nut, while the helical tooth section 5 only engages with the threads on the lead screw, and the gear engages with the internal gear ring on the nut. The cage 2 is cylindrical, with a receiving groove 11 on its cylindrical surface. The roller 3 is located within the receiving groove 11, which is designed for a small clearance fit with the roller 3 (0.05 ± 0.02 mm). This prevents the roller from deflecting due to the helix angle, thus ensuring that the gear meshing mechanism does not bear eccentric loads and that the planetary roller screw mechanism maintains stable transmission.

[0028] The specific embodiments described herein are merely illustrative examples of the present invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the spirit of this invention or exceeding the scope defined by the appended claims.

Claims

1. A reverse planetary roller screw structure comprising a screw and a nut, between which a roller is provided, characterized in that: The roller is provided with a roller thread section, and a helical tooth structure is provided on one side of the roller thread section. The lead screw is provided with a lead screw thread section, and an external gear structure is provided on one side of the lead screw thread section. The helical structure on the helical tooth structure is engaged with the nut thread on the inner surface of the nut, and the tooth structure on the helical tooth structure is engaged with the external gear. The nut is also provided with a retainer, and the retainer is provided with a receiving groove, in which the roller is located.

2. The reverse planetary roller screw structure according to claim 1, characterized in that: The transmission ratio between the helical teeth of the roller and the external gear is i. g The transmission ratio between the roller thread section and the lead screw thread section is i t i g =i t .

3. The reverse planetary roller screw structure according to claim 1, characterized in that: The retainer is cylindrical, with both ends being annular surfaces. U-shaped grooves are provided on both ends of the retainer, corresponding to receiving grooves. The receiving grooves and the U-shaped grooves at both ends are located on the same axis. The two ends of the rollers are located inside the U-shaped grooves, and the openings of the U-shaped grooves face the nut.

4. The reverse planetary roller screw structure according to claim 3, characterized in that: The roller includes a threaded section in the middle and bosses at both ends. A helical tooth is provided between the boss at one end and the threaded section. The clearance between the boss and the U-shaped groove is 0.05±0.02mm, and the clearance between the threaded section and the receiving groove is greater than 0.2mm.

5. The reverse planetary roller screw structure according to claim 1, characterized in that: The clearance between the receiving groove and the roller is 0.05±0.02mm.

6. A reverse planetary roller screw structure according to any one of claims 1 to 5, characterized in that: The nut and lead screw have ≥2 thread starts, the roller has a single-start thread, and the helix angle of the roller and the lead screw is the same.

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