ball screw nut
By differentiating between the operating and non-operating channels in the design, and only performing precision machining on the operating channel, the problem of resource waste in existing technologies is solved, enabling efficient and low-cost manufacturing of ball screw nuts and improving the stability and reliability of the transmission.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- C&U CO LTD
- Filing Date
- 2025-06-30
- Publication Date
- 2026-06-09
AI Technical Summary
Existing methods for machining ball screw nuts involve deep finishing of all internal thread areas, resulting in resource waste and low production efficiency, and failing to effectively finish the actual contact area of the balls.
Design a ball screw nut with internal thread divided into running and non-running tracks. Only the running track is precision machined, while the non-running track retains a low surface roughness. A ball circulation channel is formed by the precise connection of the circulation track and the running track, reducing unnecessary machining.
It significantly reduces processing resource consumption, improves production efficiency, reduces rework rates and product failure risks, enhances transmission stability and reliability, and conforms to the concept of green manufacturing.
Smart Images
Figure CN224339440U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to a transmission nut, and more particularly to a ball screw nut. Background Technology
[0002] Ball screw nuts are widely used in high-precision mechanical equipment, such as CNC machine tools, industrial robots, medical devices, and aerospace systems, to achieve precise linear motion conversion. In these applications, the internal thread of the nut engages with the external thread of the screw, and the rolling of the balls reduces friction and wear, thereby improving transmission efficiency and lifespan. During manufacturing, the internal thread requires precision machining to form raceways to accommodate the balls and ensure smooth movement. In use, as the screw rotates, the balls roll within the raceways of the nut's internal thread and change direction via a reversing mechanism, forming a circulating path that allows the nut to move linearly along the screw, achieving high-speed, low-friction transmission. This design is particularly suitable for industrial applications requiring high-precision positioning and reliability, such as in automated production lines or precision instruments, ensuring the stability and durability of motion control.
[0003] However, existing technologies have significant drawbacks. Because the ball screw nut has a reversing mechanism to allow the balls to circulate within the nut, certain areas of the internal thread (such as near the reversing mechanism) are not entered or contacted by the balls. Despite this, existing machining methods perform deep finishing on all internal threads, including these ineffective areas. This leads to a significant waste of machining resources, such as increased machining time, tool wear, energy consumption, and material costs, while reducing production efficiency. Optimizing the machining strategy to finish only the areas where the balls actually contact can significantly reduce waste, but existing technologies have not yet effectively solved this problem. Utility Model Content
[0004] To address the shortcomings of existing technologies, this utility model provides a ball screw nut that can save processing resources.
[0005] To achieve the above objectives, the present invention provides the following technical solution: a ball screw nut, the inner diameter surface of which is a threaded track, and the outer diameter surface of which is provided with an installation groove leading to the threaded track. A reversing device is provided in the installation groove. A circulation channel is provided on the side of the reversing device facing the threaded track, and the two ends of the circulation channel are respectively attached to the threaded track. The threaded track includes a rotating channel and a non-rotating channel. The rotating channel and the circulation channel are joined together to form a circulation channel for the ball to rotate within it. The rotating channel and the circulation channel have the same surface roughness, and the surface roughness of the two is lower than that of the non-rotating channel.
[0006] The beneficial effects of this utility model are as follows: By distinguishing between running and non-running threads, and performing high-precision finishing only on the running threads while maintaining a low surface roughness on the non-running threads, the resource consumption during processing is significantly reduced. Specifically, since the balls only move in the running and circulating threads, the non-running threads do not require fine processing. This reduces the usage time and wear of finishing tools (such as grinding wheels or grinding heads), thereby saving energy and material costs, shortening the overall processing cycle, and improving production efficiency. Furthermore, because the non-running threads are not finished, their dimensions are inconsistent with the running threads (i.e., smaller than the running threads, making it impossible to insert balls). Therefore, the balls cannot be inserted into them during assembly, thus preventing mistake-proofing during the ball insertion process in the threaded threads. This effectively reduces the probability of rework due to quality inspection and also effectively prevents product failures caused by incorrect ball assembly positions later on. As a preferred approach, during manufacturing, the entire inner diameter surface is first pre-machined using rough milling or turning to form the thread profile. Then, precision grinding equipment (such as a CNC grinder) is used to finely polish only the operating areas, ensuring a surface roughness Ra value below 0.2 μm to meet the requirements for smooth ball rolling, while non-operating areas retain a rough state with a Ra value above 1.6 μm. This selective machining method avoids over-machining by precisely positioning the operating path boundaries (e.g., using optical sensors or programmed coordinate control), achieving a highly efficient and low-cost manufacturing process. Simultaneously, this approach reduces machining waste, aligning with green manufacturing principles.
[0007] Furthermore, both ends of the circulation channel cross at least one helix in the threaded channel along the threaded channel axially.
[0008] This design ensures a smooth transition between the circulation channel and the threaded channel, allowing the balls to seamlessly transition between the running and circulation channels, avoiding jamming or skipping, thus improving the continuity and reliability of the ball movement. Specifically, after the circulation channel axially crosses multiple thread teeth, the skipped helix naturally forms a non-running channel. This simplifies the installation and positioning of the reverser, reduces the risk of assembly errors, and optimizes the geometry of the ball circulation path, reducing noise and vibration. Furthermore, this layout enhances the overall rigidity of the nut, preventing deformation under high loads. As a preferred approach, the inlet and outlet ends of the circulation channel in the reverser design employ an arc-shaped extension structure, covering at least two thread pitches axially (e.g., based on a standard leadscrew pitch design). When the reverser is inserted, the circulation channel and the running channel form a continuous curved surface, while the skipped helical area directly serves as a rough surface in the non-running channel, requiring no additional machining. This structure, through precise calculation of the span length (e.g., using CAD software to simulate the ball trajectory), ensures that the balls smoothly enter the circulation channel under centrifugal force during the transition, avoiding localized stress concentration and improving system stability.
[0009] Furthermore, the reverser includes a main body, on both sides of the main body along the axial direction of the threaded track, trunnions are provided, and the trunnions are provided with an assembly arc surface that mates with the threaded track on the side facing the threaded track. The portion of the threaded track corresponding to the assembly arc surface is a mounting arc surface, and the surface roughness of the mounting arc surface is the same as that of the running track.
[0010] This technical solution ensures that the circulation track is flush with the operating track after the reverser is installed by matching the surface roughness of the mounting arc surface with that of the operating track. This eliminates the problem of ball movement obstruction or jamming caused by uneven surfaces, thereby improving the smoothness of ball movement and the transmission efficiency of the nut. Specifically, the matching design of the mounting arc surface and the assembly arc surface prevents the circulation track from being higher or lower than the joint, reducing impact wear on the balls and extending the service life of the reverser and the nut. In addition, this simplifies the assembly process and reduces the difficulty of tolerance control. As a preferred method, the trunnion structure adopts a semi-circular protrusion design, with its assembly arc surface radius matching the curvature of the thread track (e.g., calculated based on the ball diameter). The mounting arc surface is machined using the same fine grinding process (such as diamond wheel polishing) as the operating track to ensure consistent roughness. This structure automatically aligns during assembly through the rigid support of the trunnion. When the reverser body is embedded in the mounting groove, the arc surface of the trunnion fits tightly with the thread track, forming a self-positioning mechanism to avoid micro-movement or offset, thereby maintaining the stability of the circulation track under dynamic loads.
[0011] Furthermore, the shape of the mounting groove is adapted to the main body.
[0012] This design achieves stable positioning of the reverser by matching the shape of the mounting groove with the reverser body, preventing it from detaching or shifting from the mounting groove during operation, thus ensuring the integrity of the ball circulation channel. Specifically, this adaptable structure reduces assembly clearance, improves the overall rigidity and vibration resistance of the nut, and avoids ball jamming or noise problems caused by reverser loosening. Furthermore, it simplifies the manufacturing and assembly process and reduces costs. As a preferred approach, the mounting groove is designed as a U-shaped or rectangular recess, with its inner wall contour precisely matching the shape of the reverser body (e.g., the groove width is slightly greater than the body thickness by 0.05 mm to allow for thermal expansion). After the body is inserted, mechanical locking is formed by the locking action of the trunnion. This structure, through the radial constraint of the groove wall on the body and the axial limitation of the trunnion, firmly fixes the reverser under the lateral force generated by the ball movement, avoiding radial or circumferential displacement and ensuring a seamless connection between the circulation channel and the threaded channel.
[0013] Furthermore, the circulation channel is filled with ball bearings.
[0014] This design utilizes the dense arrangement of balls to apply uniform pressure to the reverser, firmly pressing its trunnion against the threaded track. This prevents the reverser from shifting inwards or outwards in the radial direction, improving the nut's stability and load-bearing capacity. Specifically, this enhances the uniformity of ball distribution, reduces localized wear, optimizes force transmission efficiency, and avoids decreased transmission accuracy or increased noise caused by reverser wobble. Furthermore, the filled design increases the preload of the balls, adapting to high-speed or high-load conditions. As a preferred method, the balls are arranged in a standard steel ball configuration, with their diameter matching the clearance of the circulation channel (e.g., the clearance is slightly less than 1.1 times the ball diameter). When the channel is filled, the compressive force between the balls is transmitted to the trunnion through the reverser body, tightly pressing it against the threaded track. This structure, through the rigid support of the balls, creates dynamic balance during nut rotation, preventing the reverser from shifting due to centrifugal force or load changes, thus maintaining the geometric accuracy of the circulation channel.
[0015] Furthermore, the arc length of the mounting arc surface is greater than the arc length of the assembly arc surface, and the portion of the mounting arc surface arc length exceeding the assembly arc surface arc length is located on the non-operating track side.
[0016] This design effectively compensates for minor manufacturing or assembly errors by providing an additional arc length as assembly redundancy, preventing the circulation channel from protruding above the threaded channel due to positional deviations and ensuring smooth ball movement. Specifically, the excess portion is located on the non-operating channel side, avoiding interference in critical motion areas while enhancing the reverser's fault tolerance and reducing rework rates. Furthermore, this simplifies machining tolerance control and improves product yield. As a preferred approach, an extended fine grinding process is used during the machining of the mounting arc surface, increasing its arc length by 5%-10% compared to the mounting arc surface (e.g., calculated based on the standard ball radius), with the excess extending towards the non-operating channel. This structure absorbs assembly offsets (such as angular deviations during trunnion installation) by extending the arc surface. When the reverser is installed, the mounting arc surface only covers the effective area of the mounting arc surface, with the excess located on the rough non-operating channel side, not affecting the smoothness of the ball channel, thus maintaining low-friction operation under dynamic loads. Attached Figure Description
[0017] Figure 1 This is an overall structural diagram of an embodiment of the present utility model;
[0018] Figure 2 This is a partial schematic diagram of the threaded passage and circulation channel of an embodiment of the present utility model (the parts of the threaded passage with cross-sections are the non-operating passage and the mounting arc surface, respectively).
[0019] Figure 3 This is a partial schematic diagram of the threaded passage in an embodiment of the present utility model (the parts of the threaded passage with cross-sections are the non-operating passage and the mounting arc surface, respectively).
[0020] Figure 4 This is a structural diagram of the inverter according to an embodiment of the present invention. Detailed Implementation
[0021] This utility model embodiment provides a ball screw nut, such as... Figure 1-4 As shown: This ball screw nut is a mechanical component used to convert rotary motion into linear motion. Its inner diameter surface 11 is provided with a threaded passage 111. The threaded passage 111 is rough-machined into a helical groove, and then only specific parts are finished to improve efficiency. The threaded passage 111 includes a running passage 1111 and a non-running passage 1112. The running passage 1111 is the area where the ball actually rolls, while the non-running passage 1112 is the area where the ball does not enter. The non-running passage 1112 is formed by the helix that is skipped in the threaded passage 111, for example, at the crossing point of the circulation passage 133. Several mounting grooves 121 are provided on the outer diameter surface 12. Each mounting groove 121 penetrates the nut wall and leads to the threaded passage 111, for accommodating the reverser 13. The shape of the mounting groove 121 is adapted to the body 131 of the reverser 13 to ensure stable installation of the reverser 13. A reverser 13 is disposed within a mounting groove 121. The reverser 13 includes a main body 131 and a circulation channel 133 disposed on the side of the main body 131 facing the threaded passage 111. Trunnions 132 are provided on both sides of the main body 131 along the axial direction of the threaded passage 111. Each trunnion 132 has a mounting arc surface 1321 on the side facing the threaded passage 111 for mating with the threaded passage 111. The portion of the threaded passage 111 corresponding to the mounting arc surface 1321 is the mounting arc surface 1113, and the surface roughness of the mounting arc surface 1113 is the same as that of the running passage 1111. The reverser 13 has a circulation channel 133 on the side facing the threaded passage 111. Both ends of the circulation channel 133 are respectively in contact with the threaded passage 111, and both ends cross at least one helix along the axial direction of the threaded passage 111, so that the running passage 1111 and the circulation channel 133 are joined to form a circulation channel 15. The surface roughness of the running channel 1111 and the circulation channel 133 is the same and lower than that of the non-running channel 1112. This is achieved through a machining process: first, the threaded channel 111 is rough-machined as a whole, and then only the running channel 1111 and the mounting arc surface 1113 are finish-machined. The arc length of the mounting arc surface 1113 is greater than the arc length of the assembly arc surface 1321, and the excess part is located on the side of the non-running channel 1112, providing assembly redundancy. The circulation channel 15 is filled with balls (not shown in the figure), which are used to support movement and prevent displacement of the reverser 13.
[0022] In its working principle, when the lead screw rotates, the balls (not shown in the figure) roll within the circulation channel 15. The balls (not shown in the figure) enter the circulation channel 133 from the operating channel 1111, change direction under the action of the reverser 13, and return to the operating channel 1111, forming a continuous cyclic motion. Since the balls (not shown in the figure) do not roll within the non-operating channel 1112, their high surface roughness will not affect their operation, thus reducing machining requirements. The reverser 13, through the assembly arc surface 1321 of the trunnion 132, tightly engages with the mounting arc surface 1113, ensuring a smooth connection between the circulation channel 133 and the operating channel 1111, preventing the balls (not shown in the figure) from jamming. The additional arc length design of the mounting arc surface 1113 allows for assembly errors, while the filled balls (not shown in the figure) provide radial support, preventing the reverser 13 from moving.
[0023] The above embodiments are merely one preferred embodiment of the present utility model. Ordinary changes and substitutions made by those skilled in the art within the scope of the present utility model's technical solution are all included within the protection scope of the present utility model.
Claims
1. A ball screw nut, wherein its inner diameter surface is a threaded track, and its outer diameter surface is provided with a mounting groove leading to the threaded track, wherein a reversing device is provided in the mounting groove, and a circulation channel is provided on the side of the reversing device facing the threaded track, with both ends of the circulation channel respectively engaging with the threaded track, characterized in that: The threaded passage includes a running passage and a non-running passage. The running passage and the circulating passage are joined together to form a circulating channel in which the ball rotates. The running passage and the circulating passage have the same surface roughness, and the surface roughness of the two is lower than that of the non-running passage.
2. The ball screw nut according to claim 1, characterized in that: Both ends of the circulation channel cross at least one helix in the threaded channel along the axial direction of the threaded channel.
3. The ball screw nut according to claim 2, characterized in that: The reverser includes a main body, on both sides of the main body along the axial direction of the threaded track. The trunnion has an assembly arc surface that mates with the threaded track on the side facing the threaded track. The portion of the threaded track corresponding to the assembly arc surface is a mounting arc surface. The surface roughness of the mounting arc surface is the same as that of the running track.
4. The ball screw nut according to claim 3, characterized in that: The shape of the mounting groove is adapted to the main body.
5. The ball screw nut according to claim 4, characterized in that: The circulation channel is filled with ball bearings.
6. The ball screw nut according to claim 3, characterized in that: The arc length of the mounting arc surface is greater than the arc length of the assembly arc surface, and the portion of the mounting arc surface arc length that exceeds the assembly arc surface arc length is located on the non-operating track side.