Double-row planetary threaded roller bearing and axial pre-tightening adjusting method thereof
By designing annular groove threads with zero helix angle and round nuts to adjust the preload in planetary thread roller bearings, the problem of difficult preload application in planetary thread roller bearings is solved, the axial stiffness and radial load capacity of the bearings are improved, and simple preload adjustment and efficient axial stiffness are achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-06
- Publication Date
- 2026-03-10
AI Technical Summary
The existing planetary threaded roller bearings have difficulty in applying preload, resulting in insufficient axial stiffness and affecting their performance.
A double-row planetary threaded roller bearing was designed, which consists of a smooth shaft, a round nut, inner and outer bearing rings, a cage, and rollers. By setting annular groove threads with a helix angle of zero on the roller surface and the bearing surface, and adjusting the preload with the round nut, the relative axial displacement between the inner and outer rings of the bearing is achieved, simplifying the preload adjustment.
It improves the axial stiffness and radial load capacity of the bearing, reduces the rotational resistance torque, has an excellent load-volume ratio and fatigue service life, is easy to install, and reduces the complexity of the shaft system.
Smart Images
Figure CN121630898A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a double-row planetary thread roller bearing and its axial preload adjustment method, belonging to the field of bearing technology. Background Technology
[0002] Planetary threaded roller bearings are special bearings suitable for heavy-duty linear transmission mechanisms. They use threaded rollers as rolling elements and can simultaneously withstand axial and radial loads. Internally, planetary threaded roller bearings transmit loads through threads, with all thread contacts being point contacts. Compared to traditional ball bearings, planetary threaded roller bearings have more contact points within the same dimensions, enabling them to provide greater static limit load and rated dynamic load, and a single bearing can achieve bidirectional axial positioning. However, planetary threaded roller bearings require high thread machining precision. Machining errors can lead to some internal thread teeth not engaging under load, significantly affecting the axial stiffness of the bearing. Therefore, in practical applications, a certain preload needs to be applied to planetary threaded roller bearings to eliminate the clearance between the internal rolling elements and the inner and outer rings, increasing the number of effectively engaging internal thread teeth and thus improving axial stiffness.
[0003] Currently, as a novel type of bearing, planetary threaded roller bearings are still in the early stages of research, including their design methods, structural optimization, processing technology, performance analysis, and testing. Furthermore, there are no practical application cases yet. Currently, most bearings are used in practical applications by applying preload to increase their axial stiffness. However, due to structural limitations, applying preload to existing planetary threaded roller bearings is difficult. Therefore, there is an urgent need for a new type of planetary threaded roller bearing that allows for easy preload adjustment to maintain the bearing's axial stiffness. Summary of the Invention
[0004] The present invention aims to solve the problem of difficulty in applying preload in existing planetary thread roller bearings, and thus provides a double-row planetary thread roller bearing.
[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: A double-row planetary threaded roller bearing includes a shaft, a round nut, an outer bearing ring, two inner bearing rings, two cages, and several roller assemblies. The shaft is a hollow cylindrical structure. The two inner bearing rings are coaxially arranged along the axial direction and coaxially mounted on the shaft. One end of the shaft has a shoulder machined into it. The round nut is threaded onto the other end of the shaft, with one end of one inner bearing ring abutting against the shoulder surface and the round nut abutting against one end of the other inner bearing ring. The outer bearing ring is radially arranged outside the two inner bearing rings. The two cages are coaxially arranged and... It should be set between the outer ring of the bearing and the two inner rings of the bearing. The roller assembly includes main rollers and auxiliary rollers arranged coaxially along the axial direction, and the opposite ends of the main rollers and auxiliary rollers are connected. Several main rollers and several auxiliary rollers are arranged circumferentially between the outer ring of the bearing and the two inner rings of the bearing. The other end of the main rollers and the other end of the auxiliary rollers are respectively mounted on two cages. The outer surface of the main rollers, the outer surface of the auxiliary rollers, the outer surface of the inner ring of the bearing, and the inner surface of the outer ring of the bearing are respectively provided with annular groove threads with a helix angle of zero.
[0006] Furthermore, a first shaft segment is machined at one end of the main roller, and a second shaft segment is machined at the other end. A third shaft segment and a fourth shaft segment are machined at both ends of the auxiliary roller, respectively. A limiting groove is machined on the second shaft segment, and the third shaft segment is fitted into the limiting groove. The main roller and the auxiliary roller are mounted on two cages through the first shaft segment and the fourth shaft segment, respectively.
[0007] Furthermore, the axial depth of the limiting groove is greater than the axial length of the third shaft segment that it mates with, and there are axial clearances between the main roller and the auxiliary roller, as well as between the two bearing inner rings.
[0008] Furthermore, elastic washers are provided between one end of the inner ring of one bearing and the shoulder surface of the optical shaft, and between one end of the inner ring of the other bearing and the round nut.
[0009] Furthermore, annular grooves are respectively formed on opposite ends of the inner rings of the two bearings, and the elastic washers are installed in the corresponding annular grooves.
[0010] Furthermore, the primary roller is rotatably connected to one cage, and the secondary roller is rotatably connected to the other cage.
[0011] Furthermore, a flange is coaxially fixed to one end of the outer ring of the bearing, and several mounting through holes are provided on the flange along its circumference.
[0012] Furthermore, the inner walls of both ends of the outer ring of the bearing are machined with first annular grooves, and the inner walls of the opposite ends of the two inner rings of the bearing are machined with second annular grooves. Each cage is installed in the first annular groove and the second annular groove on the same side.
[0013] Furthermore, an elastic retaining ring is provided between the retainer and the first annular groove.
[0014] A method for adjusting the axial preload of the above-mentioned double-row planetary thread roller bearing includes the following steps: Step 1: Assemble the double-row planetary threaded roller bearing; Step 2: Using the flange end face as the measurement reference for the dial indicator, make the probe of the dial indicator contact the end face of the main roller that is away from the auxiliary roller, and zero the dial indicator. Step 3: Determine the magnitude of the preload based on the preload-stiffness variation curve and working conditions of the double-row planetary thread roller bearing, and calculate the axial displacement of the end face of the main roller under the action of the preload. Step 4: Continue to tighten the round nut while observing the dial indicator reading. Once the displacement of the end face of the main roller away from the secondary roller relative to the flange end face of the bearing outer ring is the calculated distance, the preload adjustment of the double-row planetary thread roller bearing is complete.
[0015] Compared with the prior art, the present invention has the following advantages: This invention proposes a novel double-row planetary threaded roller bearing, wherein the inner bore of the bearing inner ring mates with a smooth shaft, and the axial load is transmitted to the bearing inner ring through the shoulder of the smooth shaft and a round nut, and the applied preload can be adjusted using the round nut.
[0016] The outer surfaces of the main rollers, the auxiliary rollers, the inner ring of the bearing, and the inner ring of the bearing are respectively provided with annular groove threads with a helix angle of zero, which are used to transmit axial and radial loads. At the same time, since the helix angle is zero, there is no axial relative displacement between the inner ring and the outer ring of the bearing.
[0017] The annular groove threads on the main and auxiliary rollers in each roller set simultaneously mesh with the annular groove threads on the inner wall of the same bearing outer ring, and also respectively mesh with the annular groove threads on the outer walls of the two bearing inner rings. This allows for relative axial displacement between the two bearing inner rings, facilitating preload. Since both the main and auxiliary rollers contact the same bearing outer ring, bidirectional preload is possible for a single bearing in the axial direction, simplifying installation, reducing shaft system complexity, and improving axial stiffness. The double-row planetary thread roller bearing of this invention has high axial and radial load capacity, high axial stiffness, low rotational resistance torque, and excellent load-to-volume ratio and fatigue service life. Attached Figure Description
[0018] Figure 1 This is a first perspective sectional view of the double-row planetary thread roller bearing of the present invention; Figure 2 This is a second perspective sectional view of the double-row planetary thread roller bearing of the present invention; Figure 3This is a first three-dimensional structural schematic diagram of the double-row planetary thread roller bearing of the present invention; Figure 4 This is a schematic diagram of the second three-dimensional structure of the double-row planetary thread roller bearing of the present invention; Figure 5 This is a schematic front sectional view of the double-row planetary thread roller bearing of the present invention; Figure 6 A schematic sectional view of the main roller; Figure 7 This is a three-dimensional structural diagram of the auxiliary roller; Figure 8 This is a schematic sectional view of the inner ring of the bearing. Figure 9 A three-dimensional structural diagram of the cage; Figure 10 This is a three-dimensional structural diagram of the bearing outer ring; Figure 11 for Figure 5 Enlarged schematic diagram of point P.
[0019] In the picture: 1. Shaft; 11. Shoulder; 2. Round nut; 3. Bearing outer ring; 31. First annular groove; 32. Flange; 4. Bearing inner ring; 41. Annular groove; 42. Second annular groove; 5. Cage; 51. Limiting through hole; 52. Oil injection hole; 61. Main roller; 611. First shaft section; 612. Second shaft section; 613. Limiting groove; 62. Secondary roller; 621. Third shaft section; 622. Fourth shaft section; 7. Elastic washer; 8. Elastic retaining ring. Detailed Implementation
[0020] Specific implementation method one: Combining Figures 1-11 This description of embodiments provides a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0021] A double-row planetary threaded roller bearing includes a shaft 1, a round nut 2, an outer bearing ring 3, two inner bearing rings 4, two cages 5, and several roller assemblies. The shaft 1 is a hollow cylindrical structure. The two inner bearing rings 4 are coaxially arranged along the axial direction and are coaxially mounted on the shaft 1. One end of the shaft 1 is machined with a shoulder 11. The round nut 2 is threaded to the other end of the shaft 1, with one end of one inner bearing ring 4 abutting against the shoulder 11 and the round nut 2 abutting against one end of the other inner bearing ring 4. The outer bearing ring 3 is radially arranged outside the two inner bearing rings 4. The two cages 5 are coaxially arranged and correspondingly positioned. Between the outer ring 3 of the bearing and the two inner rings 4 of the bearing, the roller assembly includes main rollers 61 and auxiliary rollers 62 arranged coaxially along the axial direction. The main rollers 61 and the auxiliary rollers 62 are connected at opposite ends. A number of main rollers 61 and auxiliary rollers 62 are arranged circumferentially between the outer ring 3 of the bearing and the two inner rings 4 of the bearing. The other ends of the main rollers 61 and the auxiliary rollers 62 are respectively mounted on two cages 5. The outer surfaces of the main rollers 61, the auxiliary rollers 62, the inner rings 4 of the bearing, and the inner surface of the outer ring 3 of the bearing are respectively provided with annular groove threads with a helix angle of zero.
[0022] The cage 5 prevents the roller assembly from skewing.
[0023] The inner hole of the bearing inner ring 4 is fitted with the optical shaft 1. The axial load is transmitted to the bearing inner ring 4 through the shoulder 11 of the optical shaft 1 and the round nut 2. The applied preload can be adjusted by using the round nut 2.
[0024] The outer surfaces of the main roller 61, the auxiliary roller 62, the inner ring 4, and the outer ring 3 are respectively provided with annular groove threads with a helix angle of zero, which are used to transmit axial and radial loads. At the same time, since the helix angle is zero, there is no axial relative displacement between the inner ring 4 and the outer ring 3.
[0025] The annular groove threads on the main roller 61 and auxiliary roller 62 in each roller group simultaneously engage with the annular groove threads on the inner wall of the same bearing outer ring 3, and respectively engage with the annular groove threads on the outer walls of the two bearing inner rings 4. This allows for relative axial displacement between the two bearing inner rings 4, facilitating preload. Since both the main roller 61 and auxiliary roller 62 are in contact with the same bearing outer ring 3, bidirectional preload is possible for a single bearing in the axial direction, simplifying installation, reducing shaft system complexity, and improving axial stiffness. The double-row planetary thread roller bearing of this invention has high axial and radial load capacity, high axial stiffness, low rotational resistance torque, and excellent load-to-volume ratio and fatigue service life.
[0026] In use, the outer wall of the structural component is connected to the inner wall of the optical shaft 1. When the double-row planetary thread roller bearing rotates, the optical shaft 1 and the inner ring 4 of the bearing rotate, while the outer ring 3 of the bearing remains stationary.
[0027] The part of the optical shaft 1 that mates with the inner ring 4 of the bearing is smooth, while the part that mates with the round nut 2 is threaded.
[0028] The optical axis 1 and the inner ring of the shaft are interference fit.
[0029] The main roller 61 has a first shaft segment 611 machined at one end and a second shaft segment 612 machined at the other end. The auxiliary roller 62 has a third shaft segment 621 and a fourth shaft segment 622 machined at both ends. A limiting groove 613 is machined on the second shaft segment 612, and the third shaft segment 621 is fitted into the limiting groove 613. The main roller 61 and the auxiliary roller 62 are mounted on two cages 5 through the first shaft segment 611 and the fourth shaft segment 622, respectively. With this design, the main roller 61 and the auxiliary roller 62 are kept coaxial by the cooperation between the limiting groove 613 on the second shaft segment 612 and the third shaft segment 621. Several limiting through holes 51 are opened on the cages 5 along their circumference. The first shaft segment 611 and the fourth shaft segment 622 are respectively fitted into the limiting through holes 51 on the two cages 5 to achieve axial limiting of the roller assembly. The retainer 5 is also provided with a number of oil injection holes 52, and the number of oil injection holes 52 and the number of limiting through holes 51 are arranged at intervals. The oil injection holes 52 are used to inject grease and have the function of ventilation and heat dissipation.
[0030] The axial depth of the limiting groove 613 is greater than the axial length of the third shaft segment 621 that it mates with. There are axial clearances between the main roller 61 and the auxiliary roller 62, as well as between the two bearing inner rings 4. With this design, the axial clearances between the main roller 61 and the auxiliary roller 62, as well as between the two bearing inner rings 4, are compensation clearances. This is to compensate for the deformation and relative displacement of the roller assembly when adjusting the bearing preload. The structure is simple, the design is reasonable, and it is easy to assemble.
[0031] An elastic washer 7 is provided between one end of the inner ring 4 of one bearing and the shoulder 11 of the optical shaft 1, and between one end of the inner ring 4 of the other bearing and the round nut 2.
[0032] Annular grooves 41 are respectively formed at opposite ends of the inner rings 4 of the two bearings, and the elastic washers 7 are installed in the corresponding annular grooves 41. This design facilitates the installation of the elastic washers 7.
[0033] The main roller 61 is rotatably connected to one cage 5, and the auxiliary roller 62 is rotatably connected to the other cage 5. This design allows the main roller 61 and the auxiliary roller 62 to rotate on their own axis.
[0034] A flange 32 is coaxially fixed to one end of the outer ring 3 of the bearing, and several mounting through holes are formed along the circumference of the flange 32. In this design, the central axis of each mounting through hole is arranged parallel to the central axis of the outer ring 3 of the bearing. These mounting through holes are used to install screws in bolts to achieve axial positioning and fixation of the bearing.
[0035] The inner walls of both ends of the outer ring 3 of the bearing are machined with a first annular groove 31, and the inner walls of the opposite ends of the two inner rings 4 of the bearing are machined with a second annular groove 42. Each cage 5 is installed in the first annular groove 31 and the second annular groove 42 on the same side.
[0036] An elastic retaining ring 8 is provided between the retainer 5 and the first annular groove 31.
[0037] A method for adjusting the axial preload of the above-mentioned double-row planetary thread roller bearing includes the following steps: Step 1: Assemble the double-row planetary threaded roller bearing; First, connect the flange 32 of the outer ring 3 of the bearing to the bearing housing with several bolts or screws, specifically by tightening diagonally; Place elastic washers on the opposite end faces of the two inner rings 4 of the bearing, install the optical shaft 1, and tighten the round nut 2 until it is in close contact with the elastic washers. Step 2: Using the flange 32 end face as the measurement reference of the dial indicator, make the probe of the dial indicator contact the end face of the main roller 61 away from the auxiliary roller 62, and zero the dial indicator. Step 3: Determine the magnitude of the preload based on the preload-stiffness variation curve and operating conditions of the double-row planetary thread roller bearing, and calculate the axial displacement of the end face of the main roller 61 under the action of the preload; the formula for calculating the axial displacement is as follows:
[0038] In the formula, The maximum contact deformation of the thread teeth that contact the main roller 61 or auxiliary roller 62 with the outer ring 3 of the bearing. The tooth profile half-angle of the thread; The maximum axial deformation of the thread teeth.
[0039] Step 4: Continue to tighten the round nut 2 while observing the dial indicator reading. Once the displacement of the end face of the main roller 61 away from the auxiliary roller 62 relative to the flange 32 end face of the outer ring 3 of the bearing is the calculated distance, the preload adjustment of the double-row planetary thread roller bearing is complete.
[0040] The preload method of the present invention is applicable to double-row planetary thread roller bearings of various sizes and models.
[0041] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A double-row planetary thread roller bearing characterized by: The application relates to a hollow shaft bearing assembly, which comprises an optical shaft (1), a circular nut (2), a bearing outer ring (3), two bearing inner rings (4), two retainers (5) and a plurality of roller groups, wherein the optical shaft (1) is in a hollow cylinder structure, the two bearing inner rings (4) are coaxially arranged along the axial direction and are coaxially sleeved on the optical shaft (1), an end of the optical shaft (1) is provided with a shaft shoulder (11), the circular nut (2) is threadedly connected to the other end of the optical shaft (1), one end of one of the bearing inner rings (4) abuts against the surface of the shaft shoulder (11), and the circular nut (2) abuts against the other end of the other bearing inner ring (4), the bearing outer ring (3) is arranged on the outer side of the two bearing inner rings (4) along the radial direction, the two retainers (5) are coaxially arranged and are correspondingly arranged between the bearing outer ring (3) and the two bearing inner rings (4), the roller group comprises main rollers (61) and auxiliary rollers (62) which are coaxially arranged along the axial direction, and the opposite ends of the main rollers (61) and the auxiliary rollers (62) are butted and arranged, the plurality of main rollers (61) and the plurality of auxiliary rollers (62) are arranged between the bearing outer ring (3) and the two bearing inner rings (4) along the circumferential direction, and the other ends of the main rollers (61) and the other ends of the auxiliary rollers (62) are correspondingly mounted on the two retainers (5), and the outer surfaces of the main rollers (61), the outer surfaces of the auxiliary rollers (62), the outer surfaces of the bearing inner rings (4) and the inner surfaces of the bearing outer ring (3) are respectively provided with ring groove threads with zero helix angle.
2. A double-row planetary thread roller bearing according to claim 1, characterized in that: One end of the main roller (61) is provided with a first shaft section (611), the other end is provided with a second shaft section (612), both ends of the auxiliary roller (62) are respectively provided with a third shaft section (621) and a fourth shaft section (622), the second shaft section (612) is provided with a limiting groove (613), the third shaft section (621) is inserted into the limiting groove (613), and the main roller (61) and the auxiliary roller (62) are respectively mounted on the two retainers (5) through the first shaft section (611) and the fourth shaft section (622).
3. A double-row planetary thread roller bearing according to claim 2, characterized in that: The axial depth of the limiting groove (613) is greater than the axial length of the third shaft section (621) matched with the limiting groove (613), and there are axial gaps between the main roller (61) and the auxiliary roller (62) and between the two bearing inner rings (4).
4. A double-row planetary thread roller bearing according to claim 1, characterized in that: An elastic washer (7) is arranged between one end of one of the bearing inner rings (4) and the surface of the shaft shoulder (11) of the optical shaft (1) and between the other end of the other bearing inner ring (4) and the circular nut (2).
5. A double-row planetary thread roller bearing according to claim 4, characterized in that: Opposite ends of the two bearing inner rings (4) are respectively provided with annular grooves (41), and the elastic washers (7) are correspondingly mounted in the annular grooves (41).
6. A double-row planetary thread roller bearing according to claim 1, characterized in that: The main roller (61) and one of the retainers (5) and the auxiliary roller (62) and the other retainer (5) are rotationally connected.
7. A double-row planetary thread roller bearing according to claim 1, characterized in that: One end of the bearing outer ring (3) is coaxially fixedly provided with a flange (32), a plurality of mounting through holes are formed in the flange (32) along the circumferential direction of the flange (32).
8. A double-row planetary thread roller bearing according to claim 1, characterized in that: The inner wall of both ends of the bearing outer ring (3) is processed with a first annular clamping groove (31), the inner wall of the opposite end of each bearing inner ring (4) is processed with a second annular clamping groove (42), and each retainer (5) is installed in the first annular clamping groove (31) and the second annular clamping groove (42) on the same side.
9. A double-row planetary thread roller bearing according to claim 8, characterized in that: An elastic retainer (8) is arranged between the retainer (5) and the first annular clamping groove (31).
10. A method of adjusting the axial preload of a double-row planetary thread roller bearing according to any one of the preceding claims 1 to 9, characterized in that: The method comprises the following steps: Step one, assembling the double-row planetary threaded roller bearing; Step two, taking the end face of the flange (32) as the measuring datum of the micrometer, contacting the measuring head of the micrometer with the end face of the main roller (61) away from the secondary roller (62), and returning the micrometer to zero; Step three, determining the pre-tightening force according to the pre-tightening force-stiffness curve of the double-row planetary threaded roller bearing and the working condition, and calculating the axial displacement of the end face of the main roller (61) under the pre-tightening force; Step four, continue to tighten the round nut (2), and observe the reading of the micrometer at the same time, and when the end face of the main roller (61) away from the secondary roller (62) is displaced from the end face of the flange (32) of the bearing outer ring (3) by the calculated distance, the pre-tightening force adjustment of the double-row planetary threaded roller bearing is completed.