Planetary roller screw device
By adopting a cage-type cage and ring groove structure, the problems of numerous components and complex assembly in planetary roller screw transmission structures are solved, achieving a compact and efficient transmission design, reducing production costs and processing difficulty, and ensuring smooth motion.
Patent Information
- Application Number
- CN202520528012.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-25
- Publication Date
- 2026-02-10
- Estimated Expiration
- 2035-03-25
AI Technical Summary
Existing planetary roller screw transmission structures have many components, complex assembly processes, and high costs.
It adopts a cage-type cage and annular groove structure to replace the traditional two-end cage and snap ring. The rollers rotate freely in the roller receiving hole of the cage, and the axial position is restricted by the cooperation of the annular groove and nut to avoid deflection.
Its compact structure and high space utilization reduce processing difficulty and production costs, while ensuring smooth movement.
Smart Images
Figure CN223894915U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to a transmission structure, and more particularly to a planetary roller screw device. 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. After the rollers are installed inside the nut, they mesh with the screw and nut threads for power transmission. The axial position of the rollers is generally achieved by the internal gear ring, cage, and snap ring. These components effectively limit the axial position of the rollers within the nut and prevent roller deflection. The numerous structural components make installation complex. Summary of the Invention
[0003] This utility model provides a planetary roller screw device with a compact structure, high space utilization, reduced processing procedures, and lower production costs; it solves the technical problems of existing planetary roller screw transmission structures having many components, many assembly processes, and high costs.
[0004] The above-mentioned technical problem of this utility model is solved by the following technical solution: A planetary roller screw device includes a nut, a screw, and rollers. A cage-type cage is sleeved inside the nut. The cage is annular, and evenly distributed roller receiving holes are formed on the circumferential surface of the cage. The number of roller receiving holes is the same as the number of rollers. Rollers are installed in the roller receiving holes, and the rollers are clearance-fitted with the roller receiving holes in the axial direction. The cage-type cage replaces the original two-end cages and retaining springs, allowing the rollers to rotate freely within the roller receiving holes of the cage. Because the clearance between the roller receiving holes and the rollers is controlled within a very small range, the possibility of roller deflection is effectively avoided, ensuring the smoothness of the device's movement. Moreover, using only one cage results in a compact structure, more efficient space utilization, and a significant reduction in the machining difficulty of the planetary roller screw, reducing machining steps and thus lowering production costs.
[0005] Preferably, the inner hole of the nut is a stepped surface, with the diameters of the stepped surfaces at both ends being equal and smaller than the diameter of the stepped surface in the middle section. The stepped surface in the middle section is designed with multi-start threads. This facilitates assembly.
[0006] Preferably, inner annular grooves are provided at both ends of the nut's inner hole, and the roller is provided with an outer annular groove that mates with the inner annular grooves. The engagement of the annular grooves ensures the relative position of the roller and the nut.
[0007] Preferably, the roller has a three-section structure, with a single-start thread on the middle section of the roller that meshes with the nut and the lead screw, and outer ring grooves at both ends of the threaded section of the roller that mate with the inner ring groove on the roller.
[0008] Preferably, the threaded section of the roller has a circular arc surface to reduce friction.
[0009] Preferably, the difference between the width length of the roller receiving hole and the diameter of the roller is 'a', and the difference between the length of the roller receiving hole and the diameter of the axial length of the roller is 'b', where a > b. This effectively prevents roller deflection and improves product stability.
[0010] Therefore, the planetary roller screw device of this utility model has the following advantages: it eliminates the gear transmission part in the traditional standard planetary roller screw device, replacing it with an annular groove structure machined on the nut and rollers. The axial position is effectively restricted by the fit between the nut and rollers through the annular groove. At the same time, in terms of cage design, a cage structure is adopted, which allows the rollers to rotate freely within the groove machined on the side of the cage. Since the gap between the groove and the roller is controlled within a very small range, the possibility of roller deflection is effectively avoided, ensuring the smoothness of the device's movement.
[0011] This structure is not only compact and more efficient in space utilization, but it also effectively reduces the processing difficulty of planetary roller screws, reduces processing steps, and thus reduces production costs, providing strong support for the promotion of this type of device in practical applications. Attached Figure Description
[0012] Figure 1 This is a three-dimensional diagram of a planetary roller screw device.
[0013] Figure 2 yes Figure 1 A sectional view.
[0014] Figure 3 yes Figure 1 A cross-sectional view of the nut.
[0015] Figure 4 yes Figure 1 A cross-sectional view of the roller.
[0016] Figure 5 It is a three-dimensional diagram of the cage. Detailed Implementation
[0017] The technical solution of the utility model will be further described in detail below through embodiments and in conjunction with the accompanying drawings.
[0018] Example:
[0019] like Figure 1 and 2 As shown, a planetary roller screw device includes a nut 5, with an inner hole at the center of the nut 5, and a screw 1 coaxially arranged at the center of the nut 5. Multiple rollers 4 are evenly distributed between the screw 1 and the nut 5.
[0020] like Figure 3 As shown, the nut's inner hole is a stepped hole, with equal diameters at both ends of the stepped surface, and the diameter of the stepped surface at both ends is smaller than that of the stepped surface in the middle section. The stepped surface in the middle section has multi-start threads 45 formed for mating with the threaded section of the roller 3. The stepped surfaces at both ends have inner annular grooves 41-1 formed.
[0021] like Figure 4 As shown, the roller 4 is also designed with a three-section structure. The middle section is the threaded section 34, which meshes with the nut 5 and the lead screw. External annular grooves 31-1 are formed on both sides of the threaded section 34, and these grooves 31-1 engage with the inner annular groove 41-1 on the nut, thus ensuring the relative position of the roller 4 and the nut 5. To reduce frictional energy loss and improve transmission efficiency, the roller thread profile is designed as a circular arc surface.
[0022] like Figure 5 As shown, a cage-type retainer 3 is fitted with a clearance fit inside the nut's inner bore. The cage-type retainer 3 is annular. The axial length of the cage-type retainer 3 is greater than that of the roller. Multiple roller receiving holes 21 are evenly distributed on the circumferential surface of the cage-type retainer 3, the number of which is the same as the number of rollers 4. The roller receiving holes 21 are rectangular, and they are fitted with the rollers with a small clearance in the length direction. The difference between the width of the roller receiving hole and the diameter of the roller is 'a', and the difference between the length of the roller receiving hole and the diameter of the axial length of the roller is 'b', where a > b. This ensures that the rollers can rotate freely while preventing torsion, thus ensuring smooth movement.
[0023] Its working principle is as follows: When the lead screw rotates and the nut restricts the rotational movement, the rollers achieve planetary motion through threaded transmission, simultaneously driving the cage cage to rotate. When the rollers tend to deflect, the cage cage can correct this phenomenon, ensuring the normal operation of the screw drive. Because the rollers and the nut are fitted with annular grooves at both ends, the rollers and the nut will not have relative displacement, and ultimately the nut and rollers move axially simultaneously.
[0024] 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 planetary roller screw device, comprising a nut, a screw, and rollers, characterized in that: A cage-type retainer is fitted inside the nut. The retainer is circular and has evenly distributed roller receiving holes on its circumferential surface. The number of roller receiving holes is the same as the number of rollers. Rollers are installed in the roller receiving holes and are clearance-fitted with the roller receiving holes in the axial direction. Inner ring grooves are provided at both ends of the inner hole of the nut, and outer ring grooves that mate with the inner ring grooves are provided on the rollers.
2. The planetary roller screw device according to claim 1, characterized in that: The inner hole of the nut is a stepped surface. The diameters of the stepped surfaces at both ends are equal and smaller than the diameter of the stepped surface in the middle section. The stepped surface in the middle section is designed with multi-start threads.
3. The planetary roller screw device according to claim 1, characterized in that: The roller has a three-section structure. The middle section of the roller is provided with a single-start thread that meshes with the nut and the lead screw. The two ends of the threaded section of the roller are provided with outer ring grooves that mate with the inner ring groove on the roller.
4. A planetary roller screw device according to claim 1, 2, or 3, characterized in that: The tooth profile of the threaded section on the roller is an arc surface.
5. A planetary roller screw device according to claim 1, 2, or 3, characterized in that: The difference between the width of the roller receiving hole and the diameter of the roller is a, and the difference between the length of the roller receiving hole and the diameter of the axial length of the roller is b, where a > b.