A motor mechanism capable of fine positioning and stopping

Abstract

This invention relates to the field of planetary gear transmission technology and discloses a motor mechanism capable of precise positioning and stopping. The mechanism includes a motor, a planetary gear set, and a planetary wheel screw. The planetary gear set includes a central gear shaft and at least two planetary nuts. When the motor drives the central gear shaft to rotate, the planetary nuts move along the axial direction of the planetary wheel screw until their end faces touch the first or second positioning cover plate. At this point, the axial movement of the planetary nuts is rigidly stopped, and their rotational motion is also forcibly locked. The locking torque is then transmitted in the reverse direction to the central gear shaft and the motor's output shaft through gear meshing, stopping the entire rotational transmission chain. Because the locking occurs at a pre-set mechanical position, the stopping angle of the motor output shaft has high repeatability. Using the aforementioned structural design, precise and repeatable positioning of the endpoints of both forward and reverse rotation strokes can be achieved.

Description

Technical Field

[0001] This invention relates to the field of planetary gear transmission technology, and particularly to a motor mechanism capable of precise positioning and stopping. Background Technology

[0002] In current industrial automation and specialized machinery design, achieving high-precision stopping of rotary actuators at the end of their forward and reverse strokes typically relies on the following two technical approaches: One method involves a hydraulic motor in conjunction with a mechanical stop. For example, in the threaded core-pulling mechanism of injection molds, a hydraulic motor is commonly used to drive the mold core to rotate and retract or advance the threads. The stopping mechanism primarily relies on the mechanical interference of the mold core's own threads reaching the bottom. This method has significant drawbacks: firstly, the stopping position accuracy is low and highly susceptible to thread fit tolerances; secondly, because the hydraulic motor output torque is relatively large, it can easily lead to over-tightening of the threads, causing the mold core to jam or the threads to be damaged, making it particularly unsuitable for products with fine threads.

[0003] Secondly, servo motors combined with closed-loop control systems can achieve high-precision angle and position control, but they are expensive, have relatively small output torque, and require dedicated controllers, encoders, and complex electrical wiring and debugging processes. They also require high technical skills from operators, are inconvenient to maintain, and are difficult to widely promote in cost-sensitive or harsh operating conditions.

[0004] In addition, both of the above solutions have strong system-binding characteristics, making it difficult to flexibly attach them as independent functional modules to different types of ordinary motors (such as AC motors, DC motors, pneumatic motors, etc.). Summary of the Invention

[0005] The main objective of this invention is to provide a motor mechanism that can precisely position and stop the rotation, enabling accurate and repeatable positioning of the end point of the forward and reverse rotation stroke.

[0006] To achieve the above objectives, the present invention proposes a motor mechanism capable of precise positioning and stopping, comprising: motor; A planetary gear set includes a central gear shaft and at least two planetary nuts. The outer periphery of the central gear shaft is provided with first gear teeth, and the outer periphery of the planetary nuts is provided with second gear teeth. The first gear teeth and the second gear teeth are meshed and connected. The central gear shaft is coaxially arranged with the output shaft of the motor, and the central gear shaft is sleeved on the output shaft of the motor for receiving the rotational power input by the motor. A planetary screw rod is provided, wherein one end of the planetary screw rod is connected to a first positioning cover plate, the other end of the planetary screw rod is connected to a second positioning cover plate, a first transmission tooth is provided inside the planetary nut, and a second transmission tooth is provided on the outer periphery of the planetary screw rod, and the first transmission tooth and the second transmission tooth are meshed and connected. The first positioning cover plate and the second positioning cover plate are respectively located at the two end points of the axial movement stroke of the planetary nut. When the motor drives the central gear shaft to rotate, the planetary nut moves along the axial direction of the planetary wheel screw until its end face touches the first positioning cover plate or the second positioning cover plate, so that the central gear shaft and the motor stop rotating.

[0007] Optionally, the motor is a hydraulic motor, an electric motor, or a pneumatic motor.

[0008] Optionally, the number of planetary nuts is 2 to 6, and they are arranged at intervals along the circumferential direction of the central gear shaft.

[0009] Optionally, the central gear shaft has a module of 2 and a number of teeth of 10.

[0010] Optionally, the diameter of the central gear shaft is 24 mm.

[0011] Optionally, the tooth width of the central gear shaft is greater than or equal to the travel of the planetary nut in its axial direction.

[0012] Optionally, a fixing key is provided on the output shaft of the motor, and a keyway is provided in the central hole of the central gear shaft. At least a portion of the fixing key is embedded in the keyway, so that the output shaft of the motor and the central gear shaft are connected for transmission.

[0013] Optionally, the diameter of the star wheel screw is 12mm.

[0014] Optionally, the planetary nut has a thickness of 20 mm.

[0015] Optionally, the thickness of the first positioning cover and the second positioning cover is 5mm.

[0016] Beneficial Effects: The motor mechanism for precise positioning and stopping proposed in this invention includes a motor, a planetary gear set, and a planetary wheel screw. The planetary gear set includes a central gear shaft and at least two planetary nuts. The outer circumference of the central gear shaft is provided with first gear teeth, and the outer circumference of the planetary nuts is provided with second gear teeth. The first gear teeth and the second gear teeth mesh with each other. The central gear shaft is coaxially arranged with the output shaft of the motor and is sleeved on the output shaft of the motor to receive the rotational power input by the motor. One end of the planetary wheel screw is connected to a first positioning cover plate, and the other end of the planetary wheel screw is connected to a second positioning cover plate. The planetary nuts are provided with first transmission teeth, and the outer circumference of the planetary wheel screw is provided with second transmission teeth. The first transmission teeth and the second transmission teeth mesh with each other. The system employs a gear meshing connection. The first and second positioning cover plates are located at the two endpoints of the planetary nut's axial movement stroke. When the motor drives the central gear shaft to rotate, the planetary nut moves along the axis of the planetary wheel screw until its end face touches the first or second positioning cover plate. At this point, the axial movement of the planetary nut is rigidly stopped, and its rotation is also forcibly locked. The locking torque is then transmitted in reverse to the central gear shaft and the motor's output shaft through gear meshing, stopping the entire rotational transmission chain. Because the locking occurs at a pre-set mechanical position, the stopping angle of the motor's output shaft has high repeatability. Using the aforementioned structural design, precise and repeatable positioning of the endpoints of both forward and reverse rotation strokes can be achieved. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0018] Figure 1 This is one of the end face schematic diagrams of the motor mechanism capable of precise positioning and stopping disclosed in this application; Figure 2 This is one of the internal structural schematic diagrams of the motor mechanism capable of precise positioning and stopping disclosed in this application; Figure 3 This is the second end face schematic diagram of the motor mechanism capable of precise positioning and stopping disclosed in this application; Figure 4 This is the second schematic diagram of the internal structure of the motor mechanism capable of precise positioning and stopping disclosed in this application; Figure 5 This is the third end face schematic diagram of the motor mechanism capable of precise positioning and stopping disclosed in this application; Figure 6 This is the third schematic diagram of the internal structure of the motor mechanism capable of precise positioning and stopping disclosed in this application.

[0019] Explanation of icon numbers: 1. Motor; 2. Planetary gear set; 21. Central gear shaft; 21a. Load-bearing locking anti-slip end face; 22. Planetary nut; 3. Star wheel screw rod; 4. First positioning cover plate; 5. Second positioning cover plate; 6. Square nut; 7. Square housing; 8. Ball bearing washer; 9. Lifting screw; 10. Large nut; 11. Output gear; 12. Pressure washer; 13. Central locking component.

[0020] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0022] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0023] In this application, unless otherwise expressly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0024] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the word "and / or" throughout the text means including three parallel solutions. Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or impossible to implement, such a combination should be considered non-existent and not within the scope of protection claimed in this application.

[0025] In current industrial automation and specialized machinery design, achieving high-precision stopping of rotary actuators at the end of their forward and reverse strokes typically relies on the following two technical approaches: One method involves a hydraulic motor in conjunction with a mechanical stop. For example, in the threaded core-pulling mechanism of injection molds, a hydraulic motor is commonly used to drive the mold core to rotate and retract or advance the threads. The stopping mechanism primarily relies on the mechanical interference of the mold core's own threads reaching the bottom. This method has significant drawbacks: firstly, the stopping position accuracy is low and highly susceptible to thread fit tolerances; secondly, because the hydraulic motor output torque is relatively large, it can easily lead to over-tightening of the threads, causing the mold core to jam or the threads to be damaged, making it particularly unsuitable for products with fine threads.

[0026] Secondly, servo motors combined with closed-loop control systems can achieve high-precision angle and position control, but they are expensive, have relatively small output torque, and require dedicated controllers, encoders, and complex electrical wiring and debugging processes. They also require high technical skills from operators, are inconvenient to maintain, and are difficult to widely promote in cost-sensitive or harsh operating conditions.

[0027] In addition, both of the above solutions have strong system-binding characteristics, making it difficult to flexibly attach them as independent functional modules to different types of ordinary motors (such as AC motors, DC motors, pneumatic motors, etc.).

[0028] Based on this, this embodiment provides a motor mechanism capable of precise positioning and stopping, see [link to documentation]. Figures 1-2As shown, the motor mechanism includes a motor 1, a planetary gear set 2, and a planetary wheel screw 3. The planetary gear set 2 includes a central gear shaft 21 and at least two planetary nuts 22. The outer circumference of the central gear shaft 21 is provided with first gear teeth, and the outer circumference of the planetary nuts 22 is provided with second gear teeth. The first gear teeth and the second gear teeth mesh with each other. The central gear shaft 21 is coaxially arranged with the output shaft of the motor 1 and is sleeved on the output shaft of the motor 1 to receive the rotational power input by the motor 1. One end of the planetary wheel screw 3 is connected to a first positioning cover plate 4, and the other end of the planetary wheel screw 3 is connected to a second positioning cover plate 5. The planetary nuts 22 are provided with first transmission teeth, and the outer circumference of the planetary wheel screw 3 is provided with second transmission teeth. The first transmission teeth and the second transmission teeth mesh with each other. The connection is as follows: the first positioning cover plate 4 and the second positioning cover plate 5 are respectively located at the two end points of the axial movement stroke of the planetary nut 22. When the motor 1 drives the central gear shaft 21 to rotate, the planetary nut 22 moves along the axial direction of the star wheel screw 3 until its end face touches the first positioning cover plate 4 or the second positioning cover plate 5. At this time, the axial movement of the planetary nut 22 is rigidly stopped, and its rotational movement is also forcibly locked. Then, the locking torque is transmitted in reverse to the central gear shaft 21 and the output shaft of the motor 1 through gear meshing, so that the entire rotational transmission chain stops. Since the locking occurs at a preset mechanical position, the stopping angle of the output shaft of the motor 1 has high repeatability. With the aforementioned structural design, accurate repeatable positioning of the end points of the forward and reverse rotation strokes can be achieved.

[0029] In this embodiment, when the motor 1 drives the central gear shaft 21 to rotate, the central gear shaft 21 drives the planetary nut 22 to rotate around its own axis through gear meshing. Since the planetary nut 22 and the star wheel screw 3 are threaded together, and the star wheel screw 3 remains stationary relative to the motor 1 housing, the planetary nut 22 can generate linear displacement along the axial direction of the star wheel screw 3 while rotating. This linear displacement continues until the end face of the planetary nut 22 touches the first positioning cover plate 4 or the second positioning cover plate 5. At this time, the axial movement of the planetary nut 22 is rigidly stopped, and its rotational movement is also forcibly locked. Then, the locking torque is transmitted in reverse to the central gear shaft 21 and the output shaft of the motor 1 through gear meshing, so that the entire rotational transmission chain stops.

[0030] In this embodiment, the installation positions of the central gear shaft 21, output gear 11, clamping washer 12, central locking member 13, first positioning cover plate 4, and second positioning cover plate 5 are as follows: Figure 2 As shown.

[0031] exist Figure 2In this design, the central gear shaft 21 is a monolithic structure. "Monolithic" means that the shaft and the gear formed on it are manufactured using a single molding process, rather than combining separate gears and shafts through keys, pins, or welding. The main purpose of this monolithic structure is to significantly improve its torque-bearing capacity while meeting compact design requirements and reducing the overall radial or axial dimensions of the component. This is particularly beneficial when subjected to large and evenly distributed dynamic torque, effectively avoiding stress concentration and relative rotation problems common in split structures.

[0032] A bearing-load locking anti-slip end face 21a is formed at a predetermined locking position on the central gear shaft 21. The bearing-load locking anti-slip end face 21a is machined into a precision surface with high flatness. Furthermore, in order to prevent relative sliding or loosening, a preset anti-slip groove is engraved on the bearing-load locking anti-slip end face 21a. This anti-slip groove can be, but is not limited to, micro or macro geometric textures such as radial serrations, concentric serrations, spiral teeth, or diamond mesh patterns, to significantly increase the static friction between the locking interfaces.

[0033] The output gear 11 is mounted onto the central gear shaft 21, with one side of it facing and contacting the bearing end face of the central gear shaft 21. Then, a clamping washer 12 is fitted onto the end of the central gear shaft 21, positioned on the other side of the output gear 11. Finally, the central locking member 13 is screwed into the threaded hole at the center of the end face of the central gear shaft 21. As the central locking member 13 is gradually tightened, its nut portion applies an axial pressure downward onto the clamping washer 12, which further transmits this pressure to the corresponding end face of the output gear 11. Ultimately, the output gear 11 is firmly pressed against the bearing end face of the central gear shaft 21.

[0034] It is worth mentioning that after tightening the top screw 13, the output gear 11 installed on the central gear shaft 21 can be locked and positioned at any angle as well as the receiving output gear meshing with it.

[0035] In this locked state, the static friction between the output gear 11 and the bearing end face can overcome the circumferential torque generated during operation, thereby preventing the output gear 11 from rotating or loosening unexpectedly. After tightening the top screw 13, the output gear 11 installed on the central gear shaft 21 can be locked and positioned at any angle where it meshes with the receiving output gear. This module can also be installed on the reverse output end of a dual output shaft motor, making the output end simpler, the output shaft shorter, and the strength better.

[0036] In this embodiment, the two ends of the star wheel screw 3 are designed as square positioning heads, such as regular square or hexagonal prisms. Correspondingly, square positioning holes matching the shape are opened at corresponding positions of the first positioning cover plate 4 and the second positioning cover plate 5. During assembly, the square positioning heads at both ends of the star wheel screw 3 are inserted into the square positioning holes of the first positioning cover plate 4 and the second positioning cover plate 5 to achieve circumferential anti-rotation positioning. To further ensure the reliability of the connection, after the insertion is completed, the square positioning heads are fixedly connected to the first positioning cover plate 4 and the second positioning cover plate 5 by welding to form an integral structure. Welding can be carried out by argon arc welding, laser welding, etc., and the weld bead is ring-shaped or dot-shaped.

[0037] In another design, the two ends of the star wheel screw 3 are designed as circular threaded sections. These threaded sections pass through the central spindle holes of the first positioning cover plate 4 and the second positioning cover plate 5, and a fastening nut is screwed into their ends. By tightening the fastening nut, the star wheel screw 3 is axially pulled and fixed to the first positioning cover plate 4 and the second positioning cover plate 5. To prevent the nut from loosening due to vibration or impact, after the fastening nut is tightened in place, the junction between the fastening nut and the top of the screw is spot-welded or circumferentially welded for fixation. Alternatively, the top of the star wheel screw 3 can be directly welded to the upper surface of the first positioning cover plate 4, and the bottom of the star wheel screw 3 can be directly welded to the lower surface of the second positioning cover plate 5.

[0038] In this invention, the term "motor 1" can be defined as a power device capable of converting energy of any form into rotational mechanical energy. Depending on the specific application scenario and user requirements, the motor 1 can be a hydraulic motor, an electric motor, or a pneumatic motor.

[0039] Hydraulic motors are primarily used in high-torque, heavy-load applications, such as the thread unwinding and thread inflow operations of large threaded products in injection molds. While hydraulic motors are characterized by high power density and strong overload capacity, they typically lack precise rotational control or angle positioning capabilities. By combining the planetary gear set 2 provided in this invention with a hydraulic motor, the positioning lock occurs on a rigid limiting surface within the mechanism, rather than on the fragile core threads of the mold. Therefore, even if the hydraulic motor still outputs a large torque at the moment of locking, this torque is absorbed by the rigid contact between the planetary nut 22 and the positioning cover plate, thus preventing it from being transmitted to the working parts of the mold. This solves the problem in existing technologies where hydraulic motors easily cause core jamming and thread damage.

[0040] The application scenarios for electric motors cover various automated equipment, precision assembly lines, and small processing equipment that require frequent start-stop and positioning. Ordinary AC or DC motors are inexpensive and easy to control, but they also lack precise positioning capabilities. Traditionally, achieving precise positioning requires servo motors, which often cost several times or even tens of times more than ordinary motors and require professionals to write control programs and debug PID parameters. By installing the planetary gear set 2 and the star wheel screw 3 of this invention at the output end of an ordinary motor, the ordinary motor can achieve repeatability positioning accuracy comparable to a servo motor without any electronic closed-loop control, thereby reducing the operating cost of the equipment.

[0041] Pneumatic motors are suitable for explosion-proof environments or applications with special electrical safety requirements, such as chemical, pharmaceutical, and food processing industries. However, pneumatic motors themselves lack precise positioning capabilities, and their output speed and torque are significantly affected by fluctuations in air source pressure, making positioning even more difficult. The purely mechanical hard-limiting solution provided by this invention is unaffected by air source pressure fluctuations. As long as the torque of the pneumatic motor is sufficient to drive the planetary nut 22 to the positioning cover position, the final stopping position is always determined by the geometric accuracy of the mechanical limiting surface, independent of the air source pressure. This gives the pneumatic motor mechanism a high-precision repeatability.

[0042] In this embodiment, the planetary gear set 2 includes a central gear shaft 21 and at least two planetary nuts 22. The central gear shaft 21 serves as the driving element, used to receive the torque from the output shaft of the motor 1. The planetary nuts 22 serve as driven elements, acting as both the driven gears in the gear transmission and the driving elements in the threaded transmission, and are responsible for converting rotational motion into linear motion.

[0043] The number of planetary nuts 22 is an important parameter that determines the torque carrying capacity and structural compactness of the present invention. According to the design of the present invention, the number of planetary nuts 22 can be selected between 2 and 6, and these planetary nuts 22 are arranged at intervals along the circumferential direction of the central gear shaft 21.

[0044] When there are two planetary nuts 22, the structure is the simplest and the cost is the lowest, making it suitable for applications with small torque loads. The two planetary nuts 22 are arranged symmetrically, which can balance the radial forces on the central gear shaft 21 and reduce the off-center load on the bearing. This configuration is suitable for small automated equipment, instruments, and light transmission systems.

[0045] When there are 3 planetary nuts 22, the included angle between adjacent planetary nuts 22 is 120 degrees. This design makes the force on the central gear shaft 21 uniform, and the torque borne by each planetary nut 22 is about one-third of the total torque. It is suitable for most conventional industrial applications, such as thread unwinding of medium-sized molds and rotational positioning of packaging machinery.

[0046] When there are four planetary nuts 22, the included angle between adjacent planetary nuts 22 is 90 degrees. The four-nut configuration further distributes the total torque across four threaded pairs, thereby reducing the contact stress on each planetary nut 22 and its mating threads. Under the same total torque, the four-nut configuration can reduce the pressure on the threaded surfaces by approximately 40% to 50%, significantly extending the thread life and reducing wear and maintenance frequency. Simultaneously, because the load is distributed, the thickness of each planetary nut 22 can be reduced accordingly, making the overall mechanism more compact in axial dimensions. This configuration is particularly suitable for high-torque scenarios driven by hydraulic motors, such as threaded core-pulling mechanisms with diameters exceeding 50 mm in large injection molds.

[0047] When there are 5 or 6 planetary nuts 22, the load distribution effect is more significant, but it increases the machining accuracy requirements and assembly difficulty of the parts. The more planetary nuts 22 there are, the higher the requirements for the indexing accuracy of the central gear shaft 21 and the consistency of the thread start phase of each planetary nut 22. It is suitable for occasions that need to withstand large torque or require the transmission of large torque in an extremely thin axial space.

[0048] In this embodiment, multiple planetary nuts 22 are arranged at equal intervals. When the central gear shaft 21 drives the multiple planetary nuts 22 to rotate synchronously, the thread clearance between each planetary nut 22 and the star wheel screw 3 compensates for each other. Specifically, when the central gear shaft 21 rotates, each planetary nut 22 moves independently along the star wheel screw 3. Due to unavoidable machining errors, some planetary nuts 22 may touch the positioning cover plate first, but at this time, the other planetary nuts 22 have not yet made contact. Since the entire transmission chain is rigid, the planetary nut 22 that makes contact first will generate a slight deflection force on the central gear shaft 21 until all planetary nuts 22 are pressed against the surface of the positioning cover plate. In actual measurements, the repeatability of the stopping position of the motor mechanism using four planetary nuts 22 can reach ±0.01 mm or even higher.

[0049] In a preferred embodiment, the central gear shaft 21 has a module of 2 and 10 teeth. This design allows the central gear shaft 21 to accommodate a sufficient number of teeth within a limited gear diameter. An excessively large module can lead to overly large gears, increasing the overall size of the mechanism; an excessively small module can result in insufficient tooth strength, making it difficult to withstand the high torque impact of the hydraulic motor. A module of 2 for the central gear shaft 21 is a preferred value determined through calculation and experimental verification.

[0050] In a preferred embodiment, the diameter of the central gear shaft 21 is preferably 24 mm. This design results in a smaller moment of inertia for the central gear shaft 21, which is beneficial for rapid start-stop; at the same time, this diameter also provides sufficient installation space for the planetary nuts 22 arranged at equal intervals around it.

[0051] In this embodiment, the tooth width of the central gear shaft 21 is greater than or equal to the travel of the planetary nut 22 along its axial direction. In conventional gear transmission designs, the tooth widths of the driving gear and the driven gear are usually equal or slightly different to ensure that the meshing area covers the entire tooth width. However, in this invention, the planetary nut 22 not only rotates around its own axis but also moves along the axial direction of the planetary wheel screw 3. Therefore, the meshing position between the planetary nut 22 and the central gear shaft 21 is dynamically changing. When the planetary nut 22 is at the lower end of its travel, its second tooth meshes with the lower region of the first tooth of the central gear shaft 21; when the planetary nut 22 moves upward to the upper end of its travel, the meshing area shifts to the upper part of the tooth width of the central gear shaft 21.

[0052] If the tooth width of the central gear shaft 21 is less than the travel distance of the planetary nut 22, some teeth may disengage when the planetary nut 22 reaches its final position, leading to transmission interruption and impact loads. Therefore, in a preferred embodiment, the tooth width of the central gear shaft 21 is at least equal to the sum of the travel distance of the planetary nut 22 and the tooth width of the planetary nut 22; that is, the tooth width of the central gear shaft 21 is designed to be greater than or equal to the travel distance of the planetary nut 22 plus the tooth width of the planetary nut 22. In practical engineering, a common practice is to set the tooth width of the central gear shaft 21 to the tooth width of the planetary nut 22 plus the maximum travel distance plus a safety margin of 2 to 3 millimeters. This design ensures that the teeth of the central gear shaft 21 and the planetary nut 22 maintain full-width meshing at any position throughout the travel distance. This not only avoids stress concentration caused by changes in the meshing area but also prevents impact wear at the tooth ends due to repeated engagement and disengagement, ensuring smooth transmission and consistent torque transmission.

[0053] In this embodiment, a fixing key is provided on the output shaft of the motor 1, and a keyway is provided in the central hole of the central gear shaft 21. At least part of the fixing key is embedded in the keyway so that the output shaft of the motor 1 and the central gear shaft 21 are connected for transmission.

[0054] Specifically, the output shaft of motor 1 and the central gear shaft 21 are connected by a key and keyway joint. Specifically, the output shaft of motor 1 is provided with a key, which can be a flat key, a semi-circular key, or a guide key formed by milling, or an embedded key installed with an interference fit. Correspondingly, a keyway is provided in the center hole of the central gear shaft 21, and the shape, size, and tolerance of the keyway match those of the key. When the central gear shaft 21 is fitted onto the output shaft of motor 1, at least a portion of the key is embedded in the keyway, thereby achieving circumferential fixation between the two, allowing the torque of the motor 1 output shaft to be transmitted to the central gear shaft 21 through the shear bearing of the key.

[0055] Since the tooth width of the central gear shaft 21 is greater than the travel of the planetary nut 22, and the planetary nut 22 changes its axial meshing position with the central gear shaft 21 during movement, the keyway and the fixed key allow the central gear shaft 21 to slide axially within a limited range of the key length. This facilitates adjusting the initial meshing position of the central gear shaft 21 and the planetary nut 22 during assembly. During assembly, the central gear shaft 21 can be moved slightly to align its teeth with the teeth of the planetary nut 22.

[0056] For applications requiring the transmission of greater torque or the ability to withstand impact loads, this connection method can be improved. For example, a rectangular spline or involute spline can be used instead of a standard flat key. Spline connections offer advantages such as high load-bearing capacity, good centering, and good guidance, but their manufacturing cost is higher. Since the precision positioning and stopping mechanism provided by this invention has significantly reduced the stress level of individual parts through its multi-nut structure, a standard flat key connection can meet the requirements in most application scenarios. Under heavy loads or high-frequency forward and reverse rotation conditions, spline or double-key connections can be considered.

[0057] Furthermore, the present invention does not exclude the possibility of other connection methods. For example, a coupling, particularly a flexible coupling or a bellows coupling, can be provided between the output shaft of the motor 1 and the central gear shaft 21 to further absorb coaxiality errors and impact loads.

[0058] In this embodiment, the outer surface of the star wheel screw 3 is provided with a second transmission tooth, which is an external thread. In a preferred embodiment, the diameter of the star wheel screw 3 is 12mm. The diameter referred to here is the nominal diameter of the thread, corresponding to an M12 standard thread. The two ends of the star wheel screw 3 are respectively connected to the first positioning cover plate 4 and the second positioning cover plate 5.

[0059] In this embodiment, the diameter of the planetary wheel screw 3 is 12mm, the thickness of the planetary nut 22 is 20mm, and the thickness of the first positioning cover plate 4 and the second positioning cover plate 5 is 5mm.

[0060] In this embodiment, the first positioning cover plate 4 and the second positioning cover plate 5 are located at both ends of the planetary wheel screw 3, respectively, and together define the two endpoint positions of the axial movement of the planetary nut 22. When the end face of the planetary nut 22 touches the positioning cover plate, the entire transmission chain is mechanically locked.

[0061] When the planetary nut 22 contacts the positioning cover plate at a certain speed, the positioning cover plate needs to withstand an instantaneous impact load. The magnitude of this impact load is related to the mass of the planetary nut 22, the moving speed at the time of impact, and the stiffness of the positioning cover plate. Therefore, the positioning cover plate must have sufficient bending stiffness and shear strength to prevent plastic deformation or fracture under repeated impacts. Based on this, this embodiment uses a 5mm thick steel plate, and the material can be 45# steel or 40Cr alloy steel to ensure that the first positioning cover plate 4 and the second positioning cover plate 5 have a high bending section modulus.

[0062] Under prolonged and repeated impacts, the contact surface between the locating cover plate and the planetary nut 22 is prone to developing pits, thus altering the stopping position of the planetary nut 22. To address this issue, the contact surface of the locating cover plate can be locally hardened, for example, through high-frequency quenching, carburizing quenching, or hard chrome plating, to achieve a surface hardness of HRC50 or higher. Alternatively, a replaceable wear-resistant shim can be embedded between the locating cover plate and the planetary nut 22. The wear-resistant shim is made of tool steel or cemented carbide and precision ground in the thickness direction, with its initial thickness tolerance controlled within ±0.005 mm. When the shim wears out after long-term use, simply replacing the shim will restore the original positioning accuracy, without needing to replace the entire locating cover plate.

[0063] As the planetary nut 22 moves along the planetary wheel screw 3 under the drive of the central gear shaft 21 and gradually approaches the positioning cover plate, a small gap still exists between them. At this time, the planetary nut 22 continues to move, and the motor 1 continues to output torque. When the gap decreases to zero, the end face of the planetary nut 22 makes initial contact with the surface of the positioning cover plate.

[0064] Although this specific embodiment mainly focuses on the cooperation between the planetary gear set 2 and multiple planetary nuts 22, the basic principle of the present invention is to achieve precise positioning of the motor 1 by moving the nuts along the axial direction of the planetary gear screw 3 and contacting the rigid limiting surface. Other structural forms can also be used to achieve this. These variant solutions also fall within the protection scope of the present invention.

[0065] For example, a square nut direct drive structure, see [link / reference]. Figures 3-4As shown, in this variant, the motor mechanism includes a motor 1, a square nut 6, a square housing 7, and ball washers 8. The square housing 7 and the motor 1 are fixedly connected by bolts. The output shaft of the motor 1 is designed as a screw, or connected to a screw via a coupling. A square receiving cavity is provided inside the square housing 7, and the square nut 6 is located in the square receiving cavity. There is a certain gap between the square nut 6 and the inner wall of the square receiving cavity. The square receiving cavity restricts the rotational freedom of the square nut, allowing it to move only axially. When the motor 1 drives the screw to rotate, the square nut moves linearly axially until it touches the limiting surfaces at both ends of the square housing 7 and stops. This structure is the simplest, has the fewest parts, and is suitable for applications with low torque and cost sensitivity.

[0066] Another example is the large pitch structure of the external nut, see [link to relevant documentation]. Figures 5-6 As shown, in this variant, the motor mechanism includes a motor 1, a lifting screw 9, and a large nut 10. The large nut 10 has internal threads for engaging with the lifting screw 9, and external threads that mate with another fixed nut. When the lifting screw 9 rotates, it drives the large nut 10 to rotate, causing the large nut 10 to move axially due to the threaded engagement. By selecting large nuts 10 with different pitches, different axial feed amounts can be obtained per revolution, thus adjusting the effective number of revolutions without changing the length of the motor mechanism's housing. This structure is suitable for applications requiring flexible adjustment of the working stroke, especially those requiring frequent stroke adjustments. It is suitable for ordinary motors 1 with small to medium torque and offers advantages such as small size, low cost, and high stopping accuracy. Furthermore, the thickness of the lifting screw 9 can be easily changed to achieve precise customized forward and reverse stopping size control, facilitating maintenance and parts replacement.

[0067] Furthermore, the motor mechanism provided in this embodiment can be used to move a dual-shaft motor 1 to the tail end to achieve the same effect, making the output wheel shorter and simpler, and easier to use in various scenarios. See [link to relevant documentation]. Figure 6 As shown.

[0068] It should be noted that by controlling the height of the gearbox, the thickness of the upper and lower top plates, and the pitch of the lead screw, the number of rotations during forward and reverse rotation can be flexibly adjusted or precisely controlled, thereby meeting the high-precision positioning requirements in different scenarios. This solution supports customized precise position control for forward and reverse rotation, and features a simple structure, low cost, compact size, and wide range of applications.

[0069] In summary, the motor mechanism for precise positioning and stopping proposed in this invention includes a motor 1, a planetary gear set 2, and a shaped star wheel screw 3. The planetary gear set 2 includes a central gear shaft 21 and at least two planetary nuts 22. The outer periphery of the central gear shaft 21 is provided with first gear teeth, and the outer periphery of the planetary nuts 22 is provided with second gear teeth. The first gear teeth and the second gear teeth mesh with each other. The central gear shaft 21 is coaxially arranged with the output shaft of the motor 1 and is sleeved on the output shaft of the motor 1 to receive the rotational power input by the motor 1. The shaped star wheel screw 3 has a first positioning cover plate 4 connected to one end and a second positioning cover plate 5 connected to the other end. The planetary nuts 22 are provided with first transmission teeth, and the outer periphery of the shaped star wheel screw 3 is provided with second transmission teeth. The transmission gear and the second transmission gear mesh with each other; wherein, the first positioning cover plate 4 and the second positioning cover plate 5 are respectively located at the two end positions of the axial movement stroke of the planetary nut 22. When the motor 1 drives the central gear shaft 21 to rotate, the planetary nut 22 moves along the axial direction of the star wheel screw 3 until its end face touches the first positioning cover plate 4 or the second positioning cover plate 5. At this time, the axial movement of the planetary nut 22 is rigidly stopped, and its rotational movement is also forcibly locked. Then, the locking torque is transmitted in reverse to the central gear shaft 21 and the output shaft of the motor 1 through the gear meshing, so that the entire rotational transmission chain stops. Since the locking occurs at a preset mechanical position, the stopping angle of the output shaft of the motor 1 has high repeatability. With the aforementioned structural design, accurate repeatable positioning of the end points of the forward and reverse rotation strokes can be achieved.

[0070] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A motor mechanism capable of precise positioning and stopping, characterized in that, include: motor; A planetary gear set includes a central gear shaft and at least two planetary nuts. The outer periphery of the central gear shaft is provided with first gear teeth, and the outer periphery of the planetary nuts is provided with second gear teeth. The first gear teeth and the second gear teeth are meshed and connected. The central gear shaft is coaxially arranged with the output shaft of the motor, and the central gear shaft is sleeved on the output shaft of the motor for receiving the rotational power input by the motor. A planetary screw rod is provided, wherein one end of the planetary screw rod is connected to a first positioning cover plate, the other end of the planetary screw rod is connected to a second positioning cover plate, a first transmission tooth is provided inside the planetary nut, and a second transmission tooth is provided on the outer periphery of the planetary screw rod, and the first transmission tooth and the second transmission tooth are meshed and connected. The first positioning cover plate and the second positioning cover plate are respectively located at the two end points of the axial movement stroke of the planetary nut. When the motor drives the central gear shaft to rotate, the planetary nut moves along the axial direction of the planetary wheel screw until its end face touches the first positioning cover plate or the second positioning cover plate, so that the central gear shaft and the motor stop rotating.

2. The motor mechanism capable of precise positioning and stopping according to claim 1, characterized in that, The motor is a hydraulic motor, an electric motor, or a pneumatic motor.

3. The motor mechanism capable of precise positioning and stopping according to claim 2, characterized in that, The number of planetary nuts is 2 to 6, and they are arranged at intervals along the circumference of the central gear shaft.

4. The motor mechanism capable of precise positioning and stopping according to claim 1, characterized in that, The tooth width of the central gear shaft is greater than or equal to the travel distance of the planetary nut in its axial direction.

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