Straight cylinder type actuator

Abstract

The invention provides a straight cylinder type actuator. The straight cylinder type actuator comprises a motor, a rotating shaft assembly, a nut, an output component, a base and an axial supporting structure arranged in the base. The motor is provided with an output shaft, the rotating shaft assembly comprises a rotating shaft driven by the output shaft to rotate, and the nut is in threaded transmission through the rotating shaft, so that the rotating motion of the rotating shaft is converted into axial displacement of the nut, and the axial displacement is output to an external load through the output component. The base is arranged between the motor and the nut, and the axial supporting structure is arranged in the base and used for bearing an axial load which is generated when the nut moves in the pushing and pulling directions and is transmitted through the rotating shaft assembly and guiding the axial load into the base, so that the axial load is not directly applied to the motor or the speed reducing mechanism. Therefore, the linear push-and-pull output device can provide stable and efficient linear push-and-pull output capacity under the condition of compact appearance.

Description

Technical Field

[0001] This invention relates to an actuator. In particular, it relates to a miniature cylindrical actuator with linear output function. Background Technology

[0002] With the widespread adoption of humanoid robots, robotic arms, and precision automated equipment, micro actuators are increasingly used in space-constrained applications to perform actions such as pushing, pulling, clamping, and angle adjustment. Currently available cylindrical actuators integrate a motor and reduction mechanism within a limited radial dimension, typically enclosing the motor entirely within a housing. While this configuration protects the motor, it also limits the selectable motor diameter and power, restricting the overall output force and making it difficult to simultaneously meet the demands of high thrust output and high-efficiency operation.

[0003] On the other hand, existing actuators mostly adopt a modular housing structure, which is assembled from multiple housing components and requires precise tolerances for assembly. This design not only increases process complexity and manufacturing costs, but may also cause axial concentricity deviations due to the accumulation of tolerances, leading to decreased motion accuracy and accelerated wear. In addition, they often lack sufficient thrust bearings or load-bearing structures inside, and when subjected to push and pull loads for a long time, the contact area between the rotating shaft and the reduction gear is prone to wear or misalignment, thus limiting the load-bearing capacity and service life.

[0004] Furthermore, most existing designs directly transfer push and pull loads to the gearbox or motor, causing the axial load to actually act on the motor bearings and gearbox. This easily leads to stress concentration and structural deformation, which not only shortens the lifespan of the motor and reduction mechanism but also reduces overall motion stability. Although some improved structures attempt to increase rigidity by increasing the number of bearings or thickening parts, the increased axial space and number of parts actually weaken the advantages of miniaturization and lightweight design.

[0005] In view of this, existing cylindrical actuators still generally suffer from problems such as structural limitations, insufficient load-bearing capacity, poor heat dissipation, and tolerance accumulation. How to simultaneously improve the load-bearing capacity of push and pull forces, shorten the overall axial length, reduce the number of parts, and fully utilize the power of the motor within limited axial and radial space has become an important issue that urgently needs to be addressed and improved by those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a cylindrical actuator.

[0007] This invention provides a cylindrical actuator, characterized in that it comprises:

[0008] A motor with one output shaft;

[0009] A rotating shaft assembly includes a rotating shaft that is drively connected to the output shaft and driven to rotate by the motor;

[0010] A nut, driven by the thread of the rotating shaft, converts the rotational motion of the rotating shaft into the axial motion of the nut;

[0011] An output component, one end of which is connected to the nut, is used to output the axial movement of the nut to an external load;

[0012] A base, disposed between the motor and the nut; and

[0013] An axial support structure is provided within the base to bear the axial load generated by the nut during axial movement and transmitted through the rotating shaft assembly, and to guide the axial load into the base.

[0014] The cylindrical actuator, wherein the output component is a sleeve, one end of which is fixedly connected to the side of the nut away from the motor, and the other end is connected to an external connector to synchronously output the axial displacement of the nut to the external connector.

[0015] The aforementioned cylindrical actuator, wherein the rotary shaft assembly further includes:

[0016] A rotating shaft connector, attached to the end of the rotating shaft and rotating integrally therewith; and

[0017] An attachment part includes a body and a connecting portion protruding axially from one side of the body. The connecting portion is fixedly connected to one end of the rotating shaft connector, so that the attachment part can rotate together with the rotating shaft connector.

[0018] The cylindrical actuator has a partition in the base, and the partition has an axial through hole for the rotating shaft connector to pass through.

[0019] The aforementioned cylindrical actuator, wherein the axial support structure comprises:

[0020] At least one bushing has a flange portion extending radially outward and a cylindrical portion extending axially from the flange portion, the cylindrical portion being fitted around the outer periphery of the rotating shaft connector and capable of rotating with the rotating shaft connector; and

[0021] At least one axial support bearing assembly is provided on at least one side of the partition to bear the axial load generated by the nut during axial movement and transmitted through the rotating shaft assembly, and to guide the axial load into the base through the bushing and the axial support bearing assembly.

[0022] The aforementioned cylindrical actuator, wherein the axial support bearing assembly comprises:

[0023] A bearing housing ring is fitted onto the outer circumference of the cylindrical portion of a corresponding bushing and abuts against the partition portion;

[0024] A bearing ring is fitted onto the outer circumference of the cylindrical portion of the bushing and abuts against the flange portion of the bushing; and

[0025] A cage is provided between the bearing housing ring and the bearing shaft ring.

[0026] The aforementioned cylindrical actuator, wherein the cage includes a frame that defines an opening through which the rotating shaft connector passes, and a plurality of seat holes are provided circumferentially in the opening. Each of the plurality of seat holes accommodates a steel ball, such that each steel ball partially protrudes from both sides of the frame. The plurality of steel balls respectively form rolling contact with the bearing housing and the bearing shaft ring to support and transmit the axial load applied by the nut through the rotating shaft assembly.

[0027] The cylindrical actuator includes a radial support bearing inside the base. The radial support bearing is sleeved on the outer periphery of the rotating shaft connector and disposed in the through hole of the partition to limit the radial displacement of the rotating shaft connector relative to the base and maintain the rotational coaxiality of the rotating shaft assembly.

[0028] The aforementioned cylindrical actuator includes a reduction mechanism between the motor and the rotating shaft assembly, the reduction mechanism comprising:

[0029] A chassis, the inner circumference of which forms an internal gear ring; and

[0030] A planetary gear assembly is disposed within the chassis, the planetary gear assembly comprising:

[0031] A sun gear assembly includes a carrier and a sun gear formed on the carrier, the sun gear assembly being drively connected to the output shaft of the motor, and a plurality of locating pins being provided on one side of the carrier;

[0032] A plurality of planetary gears are arranged around the sun gear and mesh with the sun gear and the internal gear ring;

[0033] A plurality of planetary gear pins, each planetary gear pin being fixedly mounted on the body of the fastening part and providing rotational support for a corresponding planetary gear; and

[0034] A support pad is provided on the side of the plurality of planetary gears near the motor.

[0035] In the aforementioned cylindrical actuator, the fastening part is disposed on the side of the plurality of planetary gears away from the motor; a plurality of fixing holes are formed on the body of the fastening part at circumferential intervals, and a planetary gear shaft pin is respectively disposed in each of the plurality of fixing holes, so that the plurality of planetary gears are supported by each planetary gear shaft pin and clamped between the support pad and the fastening part.

[0036] The aforementioned cylindrical actuator further includes a motor adapter disposed between the motor and the reduction mechanism. The motor adapter has an axially penetrating central hole and a plurality of positioning holes spaced circumferentially along the outer edge of the central hole. The central hole is for the output shaft of the motor to pass through and be fixedly connected. The plurality of positioning holes correspond to a plurality of positioning pins disposed on one side of the sun gear component, so that each positioning pin can be inserted into the corresponding positioning hole, thereby enabling the sun gear component to be circumferentially positioned and coaxially aligned with the motor adapter.

[0037] The cylindrical actuator, wherein at least one side of the partition forms a base groove; the axial support structure includes:

[0038] At least one bushing is fitted onto the rotating shaft connector and is rotatable together with it. The bushing has a flange portion with a flange face facing the partition portion, and the flange face forms a flange groove; and

[0039] At least one retainer includes a frame body forming an opening through which the rotating shaft connector passes, and having a plurality of seat holes circumferentially provided in the opening, each of the plurality of seat holes accommodating a steel ball, such that each steel ball partially protrudes from both sides of the frame body.

[0040] The retainer is disposed between the bushing and the partition, so that the plurality of steel balls make rolling contact with the flange groove and the base groove respectively, so as to support and transmit the axial load applied by the nut through the rotating shaft assembly.

[0041] The aforementioned cylindrical actuator further includes:

[0042] A front cover, which has a plurality of front cover holes;

[0043] Multiple guide rods, one end of each guide rod is inserted through a corresponding front cover hole, and the other end is fixed to one side of the base;

[0044] A front-end housing is fitted over the nut and has a plurality of guide rod grooves formed on its inner circumference, each groove allowing a corresponding guide rod to pass through; and

[0045] A motor mounting bracket is disposed between the motor and the reduction mechanism. The motor mounting bracket is used to support and position the motor, and is fixedly connected to the chassis and the base via a plurality of fasteners.

[0046] The motor is exposed outside the front cover, the front housing, and the base.

[0047] In the aforementioned cylindrical actuator, the inner circumference of the front housing is formed with at least one keyway, and the outer circumference of the nut is provided with a key portion, which is embedded in the keyway to restrict the rotational freedom of the nut relative to the front housing and guide the nut to move in the axial direction.

[0048] This invention provides a cylindrical actuator comprising a motor, a rotating shaft assembly, a nut, an output member, a base, and an axial support structure disposed within the base. The motor has an output shaft, and the rotating shaft assembly includes a rotating shaft driven by the motor, which is kinetically connected to and rotated by the output shaft. The nut is threadedly driven by the rotating shaft directly or indirectly, converting the rotational motion of the rotating shaft into linear axial motion of the nut. The output member (e.g., a sleeve) is connected to the front end of the nut to output the axial displacement of the nut to an external connector. The base is disposed between the motor and the nut, and contains the axial support structure to withstand the axial load generated by the nut's movement in the thrust and pull directions and transmitted via the rotating shaft assembly, thus channeling the load into the base. This allows the actuator to provide stable and reliable axial drive capability within a compact form factor.

[0049] In one embodiment of the present invention, the axial support structure includes at least one bushing, at least one axial support bearing assembly, and a cage. The bushing is fitted around the outer periphery of the rotating shaft connector and has a flange portion and a cylindrical portion, and can rotate together with the rotating shaft connector. The axial support bearing assembly is disposed on at least one side of the base partition and includes a bearing housing and a bearing shaft ring, wherein the bearing housing abuts against the partition and the bearing shaft ring abuts against the flange portion of the bushing to form a double-sided axial load-bearing interface for bearing the axial load generated by the nut during axial movement and transmitted through the rotating shaft assembly, and for guiding the axial load to the base via the aforementioned bushing and axial support bearing assembly. With this independent and double-sided axial load-bearing configuration, the load of the nut in the push and pull directions is not directly applied to the reduction mechanism or motor, which helps to improve the overall structure's durability, coaxial stability, and long-term operational reliability.

[0050] In another embodiment of the invention, the axial support structure is an integrated design. At least one side of the base partition forms a base groove, while the flange portion of the bushing forms a flange groove. The cage and steel balls are disposed between the base groove and the flange groove, allowing the steel balls to form a rolling contact interface directly between the base and the bushing. This construction eliminates the need for separate bearing housings and bearing shafts, further shortening the axial arrangement space, reducing the number of parts, improving coaxiality, and enhancing load-bearing rigidity. This makes the cylindrical actuator more suitable for miniaturized, highly integrated, and space-constrained applications.

[0051] In summary, this invention, through its independent base and configured axial support structure, prevents the axial load generated by the nut during the push and pull strokes from directly acting on the reduction mechanism or motor, thereby avoiding common problems in traditional actuators such as wear, misalignment, insufficient load-bearing capacity, and shortened lifespan. Furthermore, the base of this invention can further integrate an external mounting interface, allowing the push and pull load to be directly output from the base to the external mechanism, strengthening the rigidity of the force path and the overall structural reliability of the system. Simultaneously, the motor of this invention can be at least partially exposed, not limited by the size of the housing, which not only helps improve heat dissipation efficiency but also allows for the selection of a larger power or higher performance motor to increase overall output capacity. Accordingly, this invention achieves high thrust output, durability, and miniaturized design characteristics suitable for confined spaces while maintaining a short axial length, reducing the number of parts, and increasing structural strength. Attached Figure Description

[0052] Figure 1 This is an exploded view of the straight-tube actuator according to the first embodiment of the present invention;

[0053] Figure 2 This is a cross-sectional schematic diagram of the straight-tube actuator according to the first embodiment of the present invention;

[0054] Figure 3 This is an exploded view of the straight-tube actuator according to the second embodiment of the present invention;

[0055] Figure 4 This is a three-dimensional schematic diagram of the base of the straight-tube actuator according to the second embodiment of the present invention;

[0056] Figure 5 This is a cross-sectional schematic diagram of a straight-tube actuator according to a second embodiment of the present invention;

[0057] Figure 6 This is a schematic diagram of the cylindrical actuator of the second embodiment of the present invention after assembly.

[0058] Figure 7 This is a schematic diagram illustrating the application scenario of the straight-tube actuator of the present invention in the hand of a robot.

[0059] Explanation of reference numerals in the drawings: Straight-cylinder actuator 10, 10'; Output component 12; Nut 13; Key 13a; Rotary shaft assembly 20; Rotary shaft 21; Rotary shaft connector 22; Fastening part 23; Fastening part body 231; Fixing hole 2311; Connecting part 232; Base 30; Separator 301; Base groove 301a; Through hole 302; Base connecting part 31; Radial support bearing 33; Axial support structure 40; Bushing 41; Flange 411; Flange groove 411a; Cylindrical part 412; Axial support bearing assembly 420; Bearing race 426; Bearing race groove 426a; Bearing shaft race 4 27; Bearing ring groove 427a; Cage 43; Frame 431; Opening 4311; Seat hole 4312; Steel ball 433; Motor 42; Output shaft 421; Reduction mechanism 50; Chassis 51; Internal gear ring 511; Planetary gear assembly 52; Sun gear component 53; Disc carrier 531; Sun gear 532; Locating pin 533; Planetary gear 54; Planetary gear shaft pin 55; Support washer 56; Front housing 60; Front cover 61; Guide rod groove 600; Keyway 601; Motor adapter 70; Center hole 701; Locating hole 702; External connector 80; Guide rod 81; Motor mounting base 90. Detailed Implementation

[0060] The above-mentioned objectives and structural and functional characteristics of the present invention will be described with reference to the preferred embodiments shown in the accompanying drawings. It should be particularly noted that the present invention is not limited to the structural forms disclosed in the following embodiments, and those skilled in the art can make appropriate changes without departing from the spirit and scope of the present invention.

[0061] Please refer to Figure 1 and Figure 2As shown, the first embodiment of the present invention provides a cylindrical actuator 10, mainly including a motor 42, a reduction mechanism 50, a rotating shaft assembly 20, a nut 13, an output component 12, a base 30, and an axial support structure 40. The motor 42 has an output shaft 421. The reduction mechanism 50 is arranged axially between the motor 42 and the rotating shaft assembly 20, so that the rotational output of the output shaft 421 is adjusted in speed and amplified in torque by the reduction mechanism 50 before being transmitted to the rotating shaft assembly 20. The nut 13 is directly or indirectly threadedly driven by the rotating shaft 21. This threaded transmission relationship can be a direct threaded engagement transmission between the nut 13 and the rotating shaft (lead screw) 21, or an indirect transmission transmission using balls or rollers as the medium, such as a ball screw or roller screw mechanism. This embodiment uses the direct threaded engagement (meshing) of nut 13 (not shown) on the rotating shaft of rotating shaft assembly 20 as an example. Output component 12 is connected to the end of nut 13 away from motor 42 to output the axial movement of nut 13 to an external load. Base 30 is disposed between reduction mechanism 50 and nut 13. Axial support structure 40 is disposed inside base 30 to bear the axial load transmitted by nut 13 through rotating shaft assembly 20 and to guide the axial load into base 30 to improve the overall stress stability.

[0062] In this embodiment, motor 42 can be a miniature electric motor capable of generating forward and reverse rotation when energized, with its output shaft 421 extending axially along the cylindrical actuator 10. Depending on the actual application requirements, motor 42 can be a brushless DC motor, servo motor, stepper motor, or other miniature drive motor suitable for small linear actuators, to meet different torque output, positioning accuracy, and space configuration limitations. Motor 42 includes basic drive components (not shown) such as a stator, rotor, and windings, wherein the stator is fixed inside the motor housing, and the rotor is connected to the output shaft 421, so that the output shaft 421 can be driven to rotate when energized. Through an appropriate drive control method, motor 42 can provide stable rotational output, thereby driving the subsequent rotating shaft assembly 20 to generate corresponding linear push-pull motion.

[0063] The rotary shaft assembly 20 is located on the output side of the reduction mechanism 50 and extends along the axial direction of the cylindrical actuator 10. Its main function is to receive the torque output by the reduction mechanism 50 and convert it into linear motion of the drive nut 13. In this embodiment, the rotary shaft assembly 20 includes a rotary shaft 21, a rotary shaft connector 22, and a fastening part 23, which together constitute an integrated torque transmission and load-bearing module. The reduced-speed rotary output is first transmitted to the rotary shaft 21 via the fastening part 23 and the rotary shaft connector 22. Then, the threaded engagement between the rotary shaft 21 and the nut 13 stably and accurately converts the rotary motion into a linear push-pull output to provide the actuation stroke required by the front end of the cylindrical actuator 10.

[0064] The rotating shaft connector 22 is disposed on the side of the rotating shaft 21 near the motor 42 and rotates integrally with the rotating shaft 21. The rotating shaft connector 22 is fixedly connected to the fastening part 23, so that the rotating shaft connector 22 can directly receive the reduced torque output by the planetary gear assembly 52 through the fastening part 23. The outer diameter of the rotating shaft connector 22 is smaller than that of the rotating shaft 21 to form a narrow-diameter connecting section, which allows it to pass through the through hole of the partition portion of the base 30 and interface with the axial support structure 40 in this area to bear and transmit the axial load. The rotating shaft connector 22 and the rotating shaft 21 can be integrally formed, or they can be separate components and fixedly assembled by interference fit, keying, or screwing. The present invention does not limit this.

[0065] The rotating shaft 21 is located on the side of the rotating shaft connector 22 away from the motor 42 and is an axially extending shaft. The outer circumference of the rotating shaft 21 has an external thread (not shown) for threaded engagement with the internal thread (not shown) on the inner circumference of the nut 13. After assembly, the front end of the rotating shaft 21 extends from the base 30, allowing the nut 13 to be fitted and threadedly engaged with the rotating shaft 21. When the rotating shaft 21 is driven to rotate by the reduction mechanism 50, the nut 13 experiences a linear axial displacement due to the threaded engagement, thus completing the conversion from rotary motion to linear motion to provide the push-pull output stroke required by the actuator front end.

[0066] The fastening part 23 is disposed on the side of the rotating shaft connector 22 near the reduction mechanism 50, and includes a body 231 and a connecting portion 232 protruding axially from the body 231. The connecting portion 232 is fixedly engaged with the rotating shaft connector 22, so that the fastening part 23 can rotate synchronously with the rotating shaft connector 22. The body 231 may be disc-shaped or other geometric configurations suitable for supporting the planetary gear assembly, and the present invention is not limited thereto. The fastening part 23 provides a positioning and support interface for the planetary gear assembly and serves as a torque transmission reference on the output side of the reduction mechanism 50. Its specific functions and structure will be further detailed in the subsequent paragraphs concerning the reduction mechanism 50.

[0067] In summary, the rotary shaft assembly 20, consisting of the rotary shaft 21, rotary shaft connector 22, and fastening part 23, bears the torque amplified by the motor 42 via the reduction mechanism 50 and transmits it to the nut 13. The threaded engagement between the rotary shaft 21 and the nut 13 is responsible for converting the motion mode, forcibly converting the rotational motion of the rotary shaft 21 into the linear axial displacement of the nut 13. Through this structure, the rotary shaft assembly 20 can drive the nut 13 to achieve bidirectional push and pull actuation functions and provide a reliable linear motion reference for the front end output of the cylindrical actuator 10.

[0068] Nut 13 is located at the front end of the cylindrical actuator 10. Its body forms an axially penetrating hollow hole, and an internal thread (not shown) is machined into its inner circumference to engage with the external thread (not shown) of the rotating shaft 21. Through this threaded engagement, nut 13 can move axially back and forth according to the rotation direction of the rotating shaft 21, achieving bidirectional actuation of pushing and pulling. For example, when the rotating shaft 21 uses a right-hand thread, if the motor 42 drives the rotating shaft 21 to rotate clockwise, nut 13 will be pushed forward axially; conversely, when the rotating shaft 21 rotates counterclockwise, nut 13 will retract axially towards the rear. To prevent nut 13 from rotating synchronously with the rotating shaft 21 during the aforementioned push-pull displacement, the present invention provides a guide structure on the outer circumference of nut 13 to restrict its circumferential degree of freedom, ensuring that nut 13 moves only axially, thereby ensuring threaded drive efficiency and linear positioning accuracy.

[0069] In this embodiment, the aforementioned guiding structure can be formed by at least one key portion 13a formed on the outer periphery of the nut 13, which engages with a corresponding keyway 601 formed on the inner periphery of the front housing. Through the engagement of the key portion 13a and the keyway 601, the nut 13 can only slide axially under the drive of the rotating shaft 21 without circumferential rotation, thereby enabling the thread engagement to stably convert the rotational motion into linear displacement, and output the push-pull force to the external load through the output member 12.

[0070] Output component 12 is disposed at the front end of nut 13, serving as the output end component of cylindrical actuator 10. It transmits the axial displacement generated by nut 13 to external connector 80 and outputs a corresponding push-pull action. In this embodiment, output component 12 can be, for example, a hollow sleeve with an axial through hole formed in its body, and its rear end is fixedly connected to nut 13, for example, by threaded connection, plug-in fixation, or other fixing methods that provide a reliable connection. This invention is not limited to a specific method. When nut 13 moves axially, output component 12 also synchronously generates linear displacement in the same direction to accurately output this axial movement to the external mechanism. Furthermore, the front end of output component 12 can be designed with various external connection forms according to application requirements, such as ball joints, fork joints, threaded ends, or other mechanical interconnect interfaces, thereby improving overall installation compatibility and flexibility in motion applications.

[0071] The base 30 is an independent load-bearing and support component of the cylindrical actuator 10, located between the motor 42 and the nut 13, to support the reduction mechanism 50, the rotary shaft assembly 20, and related components of the axial support structure 40. The base 30 has a hollow structure, with a centrally defined axially extending receiving area to accommodate components such as the rotary shaft connector 22, the axial support structure 40, and the radial support bearing 33. A partition 301 is formed inside the base 30, with a centrally located axially penetrating through hole 302 for the rotary shaft connector 22 to pass through, allowing the rotary shaft assembly 20 to extend from the reduction mechanism 50 to the outside of the base 30, and enabling the rotary shaft 21 to engage with the nut 13 via threads. By means of the geometric configuration of the partition 301 and the through hole 302, the rotating shaft connector 22, the axial support structure 40 and the radial support bearing 33 can jointly form a stable support surface and load transmission path in the base 30, so as to ensure that the rotating shaft assembly 20 maintains good coaxial stability during operation.

[0072] In this embodiment, at least one base connection portion 31 may be formed on the outer side of the base 30. This base connection portion 31 is disposed on the outer surface of the base 30 and constitutes the main fixing interface between the cylindrical actuator 10 and the external structure. Since the axial load generated by the nut 13 during the push and pull strokes is introduced into the base 30 through the rotating shaft connector 22 and the axial support structure 40, the base connection portion 31 can directly transmit this axial load to the external structure, instead of applying it to non-load-bearing components such as the reduction mechanism 50, the motor 42 housing, or the front housing 60. This avoids unnecessary axial stress on non-load-bearing components, improves the rigidity of the overall force path, reduces fatigue damage, and extends the overall service life of the cylindrical actuator 10.

[0073] An axial support structure 40 is disposed inside the base 30 to bear the axial load generated by the nut 13 during axial movement and transmitted through the rotating shaft assembly 20, and to guide the axial load into the base 30. The axial support structure 40 mainly includes at least one bushing 41, at least one axial support bearing assembly 420 and a cage 43, which together form a stable bidirectional axial load-bearing interface.

[0074] The axial support bearing assembly 420 is disposed on at least one side of the partition 301, and is composed of a bearing housing ring 426 and a bearing shaft ring 427 that cooperate with each other, and together with the cage 43 described later, forms a rolling support interface that bears push and pull axial loads.

[0075] The cage 43 includes a frame 431 with a central opening 4311 for the rotating shaft connector 22 to pass through. A plurality of mounting holes 4312 are formed circumferentially around the frame 431, each mounting hole 4312 housing a steel ball 433, with portions of the steel ball 433 protruding from both sides of the frame 431. After assembly, each steel ball 433 forms a rolling contact interface with the grooves (426a, 427a) on the corresponding surfaces of the bearing housing 426 and the bearing shaft ring 427, thereby bearing and smoothly transmitting axial loads.

[0076] This embodiment uses the configuration of two bushings 41 and two sets of axial support bearing assemblies 420 as an example. The two sets of axial support bearing assemblies 420 are respectively arranged on opposite sides of the partition 301, so that the rotating shaft assembly 20 has corresponding axial bearing capacity in both pushing and pulling directions, ensuring that it can maintain motion stability when subjected to force in different directions.

[0077] Two bushings 41 are respectively fitted onto the outer periphery of the rotating shaft connector 22. Each bushing 41 has a hollow sleeve structure, including a flange portion 411 extending radially outward and a cylindrical portion 412 extending axially from the flange portion 411. The inner hole of the cylindrical portion 412 allows the rotating shaft connector 22 to pass through, so that the bushing 41 can be fixed to the outer periphery of the rotating shaft connector 22 and rotate with it. The outer periphery of the cylindrical portion 412 provides a mounting reference for the bearing housing ring 426 and the bearing shaft ring 427, so that they can be respectively fitted onto the outer periphery of the cylindrical portion 412. After assembly, the bearing shaft ring 427 abuts against the flange portion 411 of each bushing 41, while the bearing housing ring 426 abuts against the partition portion 301, and the flange portion 411 and the cylindrical portion 412 together form a stable axial bearing interface.

[0078] The cage 43 is disposed between the bearing housing ring 426 and the bearing shaft ring 427, so that the steel balls 433 form rolling contact on the corresponding interface to support the thrust or pull generated by the rotating shaft connector 22 along the axial direction, while effectively reducing the coefficient of friction and suppressing the coaxiality deviation of the rotating shaft assembly 20.

[0079] Through the synergistic action of bushing 41, bearing housing 426, bearing shaft 427 and cage 43, the axial support structure 40 provides stable, low-friction and high-coaxiality support when the rotating shaft assembly 20 bears axial load, enabling the cylindrical actuator 10 to have excellent durability, load-bearing capacity and output smoothness.

[0080] When the rotating shaft 21 rotates under the drive of the reduction mechanism 50, the nut 13 is pushed or pulled by engaging with the thread of the rotating shaft 21, moving axially relative to the rotating shaft 21, and applying a pushing or pulling force outward through the output component (e.g., sleeve) 12 and the external connector 80. The reaction force of the external load is transmitted axially back to the nut 13, and then transmitted to the rotating shaft 21 through the internal thread of the nut 13, and then guided into the rotating shaft connector 22 through the integral or fixed connection between the rotating shaft 21 and the rotating shaft connector 22. At this time, the axial load borne by the rotating shaft connector 22 is transmitted to the bearing ring 427 through the flange portion 411 of the bushing 41, and then transmitted to the bearing housing 426 by the rolling of the steel balls 433 of the cage 43, and finally guided into the base 30 by the partition portion 301 abutted by the bearing housing 426. Through this load transmission path, the axial loads generated by the nut 13 in the push and pull directions can be effectively transferred to the base 30, instead of being applied to the bearings of the reduction mechanism 50 or the motor 42, thereby improving the overall durability and reliability.

[0081] In this embodiment, to suppress radial wobble that may occur when the rotating shaft assembly 20 operates at high speed or is subjected to eccentric loads, and to maintain the coaxiality of the rotating shaft 21 relative to the base 30, a radial support bearing 33 is provided in the through hole 302 of the partition 301. The inner ring of the radial support bearing 33 is fitted around the outer periphery of the rotating shaft connector 22, and the outer ring is supported by the partition 301, so that the rotating shaft connector 22 can obtain stable radial positioning during rotation, thereby improving the overall motion accuracy and the stress stability of the axial support structure 40.

[0082] The reduction mechanism 50 is located between the motor 42 and the rotating shaft assembly 20. Its main function is to convert the high-speed, low-torque output of the motor 42 into a low-speed, high-torque rotary output, so that the straight-tube actuator 10 can still provide sufficient thrust output within the limited structural space to meet the application requirements of precision linear drive.

[0083] The reduction mechanism 50 mainly includes a housing 51 and a planetary gear assembly 52 disposed in the housing 51. The planetary gear assembly 52 achieves the desired reduction ratio and output torque increase through the meshing of the sun gear, planetary gears and internal gear ring.

[0084] The chassis 51 is a hollow shell with an annular internal gear ring 511 forming its inner circumference, providing the meshing reference for the planetary gear 54. The geometry of the chassis 51 and the module of the internal gear ring 511 are designed according to the meshing requirements of the planetary gear assembly 52, so that the planetary gear 54 can maintain correct tooth surface contact within the chassis 51. The outer circumference of the chassis 51 can be fixed together with the base 30, motor mounting bracket, and other components by means of fasteners to maintain the stable positioning of the reduction module in the overall device.

[0085] In this embodiment, in order to ensure that the output shaft 421 of the motor 42 can be stably connected to the sun gear 53 in the reduction mechanism 50, and to ensure that the two maintain accurate coaxiality and circumferential positioning after assembly, the present invention provides a motor adapter 70 between the motor 42 and the reduction mechanism 50.

[0086] The motor adapter 70 serves as the intermediary interface between the motor 42 and the reduction mechanism 50. A central hole 701 is formed in its center, through which the output shaft 421 passes and is fixedly connected, allowing the rotational torque output by the motor 42 to be directly transmitted to the sun gear assembly 53. Furthermore, a plurality of positioning holes 702 are formed circumferentially at intervals along the outer edge of the motor adapter 70. Each positioning hole 702 corresponds to a plurality of positioning pins 533 provided on one side of the disc-shaped carrier 531 of the sun gear assembly 53, allowing the positioning pins 533 to be inserted into the corresponding positioning holes 702. This ensures precise circumferential positioning and coaxial alignment of the sun gear assembly 53 relative to the motor adapter 70, thereby maintaining the stability and geometric accuracy of the planetary gear assembly 52 during operation.

[0087] The planetary gear assembly 52 includes a sun gear 53, a plurality of planetary gears 54, a plurality of planetary gear pins 55, and a support washer 56. The sun gear 53 includes a disc-shaped carrier 531 and a sun gear 532 formed thereon. The sun gear 53 is precisely positioned circumferentially by a plurality of locating pins 533 arranged circumferentially on one side of the disc-shaped carrier 531, which are inserted into the locating holes 702 of the motor adapter 70. When the motor 42 is running, its output shaft 421 drives the motor adapter 70 to rotate, which in turn drives the sun gear 53 and the sun gear 532 to rotate synchronously, providing the central drive required for the operation of the planetary gears 54.

[0088] The disc-shaped body 231 of the aforementioned fastening part 23 has a plurality of fixing holes 2311 formed circumferentially. Each fixing hole 2311 is used to insert a planetary gear shaft pin 55, so that the plurality of planetary gears 54 can be arranged in a ring around the sun gear 532 and rotated for support. In the assembled state, each planetary gear 54 is clamped in the axial direction by a support pad 56 on one side near the motor 42 and a fastening part 23 on the other side, to form a controlled axial positioning interface. In addition to limiting the axial movement of the planetary gears 54, the support pad 56 can also provide appropriate friction buffering during high-speed operation, so that the planetary gears 54 maintain a stable posture and good meshing angle, thereby improving the overall transmission efficiency and operational reliability of the reduction mechanism 50.

[0089] In this embodiment, to ensure stable guidance and circumferential restriction during the axial movement of the nut 13, a front end housing 60 of a cylindrical actuator 10 is provided. The front end housing 60 is disposed in the front end region of the cylindrical actuator 10, and can be, for example, a hollow square cylindrical member. Inside, a cylindrical cavity is formed that matches the outer periphery of the nut 13, allowing the nut 13 to slide axially within this cavity in a restricted and guided manner. The front end housing 60 covers the nut 13 and the output member 12, providing a fixed geometric boundary for the nut 13 to improve the stability of its axial movement and serve as a circumferential restriction and guiding positioning structure.

[0090] A plurality of guide rod grooves 600 are formed at the four corners of the inner periphery of the front housing 60. Each guide rod groove 600 extends axially, and its cross-section can be, for example, a rounded elongated groove. The width and shape match the outer diameter of the guide rod 81, allowing the guide rod 81 to pass through and providing a linear positioning reference for the front housing 60. The guide rod 81 is a fixed component and does not move with the nut 13 or other moving parts. When the nut 13 slides axially inside the front housing 60, it obtains stable guidance through the geometric constraint of the front housing 60 relative to the guide rod 81. In this embodiment, a keyway 601 is formed on the groove wall of one of the guide rod grooves 600. The cross-section of the keyway 601 is a narrower cuboid groove structure than that of the guide rod groove 600, and it is continuously adjacent to the guide rod groove 600 in the form of a groove, so that there is no need to set a separate keyway area on the inner periphery of the front housing 600. The width and depth of the keyway 601 correspond to the key portion 13a formed on the outer periphery of the nut 13, allowing the key portion 13a to slide and engage within the keyway 601. The engagement between the key portion 13a and the keyway 601 effectively restricts the circumferential freedom of the nut 13, preventing it from rotating or shifting during axial movement, thus ensuring precise, smooth, and coaxial thread engagement between the nut 13 and the rotating shaft 21.

[0091] To further improve the guiding accuracy of the nut 13 during axial movement, this embodiment further includes a front cover 61, which, together with the plurality of guide rods 81 and the front housing 60, constitutes the linear guiding structure of the cylindrical actuator 10. The front cover 61 is disposed in front of the front housing 60, forming a plurality of front cover holes (not labeled in the figure). One end of each guide rod 81 passes through the corresponding front cover hole (not labeled in the figure), and the other end is fixed to the front fixing hole (not labeled in the figure) of the base 30, so that the guide rods 81 form a set of axially extending and fixed guiding references. The guide rod groove 600 formed on the inner circumference of the front housing 60 allows the guide rods 81 to pass through and be positioned, thereby maintaining the stable positioning of the front housing 60. The nut 13 slides axially within the cavity of the front housing 60 and is circumferentially restricted by its outer peripheral guiding structure (e.g., key 13a) in conjunction with the keyway 601 of the front housing 60, so that it can maintain precise, non-wobbling linear motion under the drive of the rotating shaft 21, ensuring the stability of the thread engagement relationship and the smoothness of the movement.

[0092] This embodiment further includes a motor mounting base 90 to provide stable support for the motor 42 within the overall device. The motor mounting base 90 is positioned between the motor 42 and the reduction mechanism 50, and it has mounting holes (not shown) and positioning surfaces to support and position the motor 42. It can be connected and fixed to the housing 51 and base 30 via multiple fixing members (not shown). This structure prevents the motor 42 from shifting due to vibration or external loads during operation, maintaining good coaxiality and structural stability. Furthermore, because this invention employs a multi-component combination structure including a front cover 61, a front housing 60, and a base 30, the motor 42 can be exposed outside these components, reducing the overall axial length and improving heat dissipation and installation flexibility.

[0093] Please refer to Figures 3 to 6 As shown, the overall structure of the cylindrical actuator 10' of the second embodiment of the present invention is largely the same as that of the cylindrical actuator 10 of the first embodiment, with the main difference being the configuration of the axial support structure 40. In the second embodiment, the bearing race 426 and bearing shaft race 427 used in the original first embodiment are omitted, and instead, the flange groove 411a formed by the flange portion 411 of the bushing 41 and the base groove 301a formed on the base partition portion 301 directly form the rolling contact interface of the steel ball 433. This configuration simplifies the structure by reducing the number of parts and shortens the overall axial length.

[0094] like Figure 3 As shown, in the second embodiment, the bushing 41, in addition to having a flange portion 411 extending radially outward, has a flange portion 4111 with a circumferentially surrounding flange groove 411a machined on the side facing the partition portion 301 to provide a rolling contact interface for the steel ball 433. Meanwhile, as... Figure 4 and Figure 5 As shown, a base groove 301a is also formed at a corresponding position in the partition portion 301 of the base 30. The base groove 301a is arranged circumferentially around the surface of the partition portion 301 and corresponds to the flange groove 411a. By the correspondence between the flange groove 411a and the base groove 301a, the rolling track of the steel ball 433 can be defined, so that the steel ball 433 can roll stably and with low friction between the two opposing grooves.

[0095] The retainer 43 used in this embodiment is the same as that in the first embodiment, including a frame body 431, a central opening 4311, and a plurality of seat holes 4312. Each seat hole 4312 accommodates a steel ball 433, with the steel ball 433 partially exposed on opposite sides of the frame body 431. Unlike the first embodiment, in this embodiment, the retainer 43 is disposed between the flange portion 411 of the bushing 41 and the partition portion 301 of the base 30, so that the steel ball 433 can form a rolling contact interface with the flange groove 411a and the base groove 301a respectively, so as to withstand the axial load applied by the rotating shaft assembly 20 in the push and pull directions.

[0096] This embodiment, by omitting the bearing housing and bearing shaft, allows the steel balls 433 to directly roll in contact between the bushing 41 and the base 30 partition 301. This not only reduces the number of parts and manufacturing complexity but also shortens the thickness of the axial support structure 40, making the overall mechanism more compact. This configuration still provides sufficient bidirectional axial rolling support capacity, ensuring that the rotating shaft assembly 20 maintains low friction and high stability during push-pull movements.

[0097] Since the steel ball 433 directly contacts the bushing 41 and the base 30, the load transmission path is more direct and the rigidity is higher, which can effectively reduce the deformation of the component under stress and improve the coaxiality maintenance capability of the rotating shaft assembly 20. This structure not only improves durability, but also further enhances the operational stability of the straight-tube actuator 10' under long-term repeated push-pull actions.

[0098] Please refer to Figure 6 As shown, the cylindrical actuator 10' in this embodiment is a miniature cylindrical actuator. After assembly, it can be a long and narrow rectangular (or polygonal or circular) cylindrical component, with its main modules arranged sequentially from the front end to the rear end along the axial direction. This cylindrical actuator 10' is designed for applications with limited installation space, such as humanoid robot hands, mechanical fingers, and precision automated equipment. Its outer diameter ranges from approximately 8 to 20 millimeters (mm), and its total axial length is approximately 40 to 120 mm. However, the actual size can be adjusted according to application requirements and is not limited to a specific size configuration. In the front end region, the nut 13 and the output component (e.g., sleeve) 12 are combined to form the output end, which is used to output the linear displacement generated by the nut 13 to the external mechanism. The middle section sequentially includes a front end housing 60, a base 30, and a reduction mechanism 50. In addition to accommodating the rotating shaft connector 22 and the axial support structure 40, the base 30 also forms a base connection portion 31 on its outer side, which serves as a fixed interface for the overall device to withstand push and pull loads. In the rear end region, the motor mounting base 90 supports and positions the motor 42, so that the motor 42, the reduction mechanism 50 and the rotary shaft assembly 20 can be kept in a coaxial configuration, ensuring that the assembled cylindrical actuator 10' has a stable force flow path during push-pull movements.

[0099] Please refer to Figure 7 As shown, Figure 7 This is a schematic diagram of the cylindrical actuator 10' of the present invention applied to a robot hand. As shown, a plurality of cylindrical actuators 10' can be respectively configured in the internal cavities of the robot hand or fingers, and the output component 12 at the front end of each actuator 10' is connected to the corresponding finger joint mechanism. By independently pushing and pulling each cylindrical actuator 10', the joints can be driven to produce compound movements such as bending and extension, thereby achieving high degree of freedom and biomimetic robot hand control. The cylindrical actuator 10' of the present invention has the advantages of short axial length, high thrust, miniaturization and high coaxiality stability, making it particularly suitable for the narrow installation space within the hand, and can improve the overall response speed, precision and efficiency of hand movements.

[0100] The cylindrical actuator of the present invention, through the synergistic effect of the rotary shaft assembly, axial support structure, and planetary reduction mechanism provided in the first embodiment, provides high thrust output and high-precision linear positioning within a limited volume. The bidirectional axial support interface formed by the rotary shaft connector, bushing, cage, and multiple steel balls allows the axial load generated by the nut during the push and pull strokes and transmitted through the rotary shaft assembly to be stably guided to the base, rather than being directly applied to the motor or reduction mechanism. This load path effectively improves the durability of the mechanism; at the same time, the radial support bearing arranged in the partition can suppress eccentricity and vibration during high-speed operation, maintaining good coaxiality and smooth movement between the rotary shaft and the nut.

[0101] Furthermore, the second embodiment further integrates the axial support structure without altering the overall motion principle and load transmission path: the bearing ring and bearing housing ring, which were separately arranged in the first embodiment, are integrated into the bushing flange and base partition, respectively, so that the flange forms a flange groove and the partition forms a base groove, directly serving as the rolling contact interface for the steel balls. This integrated structure not only reduces the number of parts and the complexity of processing and assembly, but also shortens the axial length and improves structural rigidity. Despite the reduced number of parts, the second embodiment still provides the same bidirectional load-bearing capacity, load transmission efficiency, low-friction rolling characteristics, and rotational coaxiality as the first embodiment, and is more suitable for small actuator applications that require ultra-short stroke, ultra-thin design, or high integration.

[0102] The present invention has been described in detail above, but the above description is only a preferred embodiment of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made based on the present invention should still fall within the patent coverage of the present invention.

Claims

1. A cylindrical actuator, characterized in that, include: A motor with one output shaft; A rotating shaft assembly includes a rotating shaft that is drively connected to the output shaft and driven to rotate by the motor; A nut, driven by the thread of the rotating shaft, converts the rotational motion of the rotating shaft into the axial motion of the nut; An output component, one end of which is connected to the nut, is used to output the axial movement of the nut to an external load; A base, disposed between the motor and the nut; and An axial support structure is provided within the base to bear the axial load generated by the nut during axial movement and transmitted through the rotating shaft assembly, and to guide the axial load into the base.

2. The straight-tube actuator as described in claim 1, characterized in that, The output component is a sleeve, one end of which is fixedly connected to the side of the nut away from the motor, and the other end is connected to an external connector to synchronously output the axial displacement of the nut to the external connector.

3. The straight-tube actuator as described in claim 1, characterized in that, The rotating shaft assembly also includes: A rotating shaft connector, attached to the end of the rotating shaft and rotating integrally therewith; and An attachment part includes a body and a connecting portion protruding axially from one side of the body. The connecting portion is fixedly connected to one end of the rotating shaft connector, so that the attachment part can rotate together with the rotating shaft connector.

4. The straight-tube actuator as described in claim 3, characterized in that, The base has a partition with an axial through hole for the rotating shaft connector to pass through.

5. The straight-tube actuator as described in claim 4, characterized in that, The axial support structure includes: At least one bushing has a flange portion extending radially outward and a cylindrical portion extending axially from the flange portion, the cylindrical portion being fitted around the outer periphery of the rotating shaft connector and capable of rotating with the rotating shaft connector; and At least one axial support bearing assembly is provided on at least one side of the partition to bear the axial load generated by the nut during axial movement and transmitted through the rotating shaft assembly, and to guide the axial load into the base through the bushing and the axial support bearing assembly.

6. The straight-tube actuator as described in claim 5, characterized in that, The axial support bearing assembly includes: A bearing housing ring is fitted onto the outer circumference of the cylindrical portion of a corresponding bushing and abuts against the partition portion; A bearing ring is fitted onto the outer circumference of the cylindrical portion of the bushing and abuts against the flange portion of the bushing; and A cage is provided between the bearing housing ring and the bearing shaft ring.

7. The straight-tube actuator as described in claim 6, characterized in that, The cage includes a frame that defines an opening through which the rotating shaft connector passes, and a plurality of seat holes are provided circumferentially in the opening. Each of the plurality of seat holes accommodates a steel ball, with each steel ball partially exposed from both sides of the frame. The plurality of steel balls form rolling contact with the bearing housing and the bearing shaft respectively to support and transmit the axial load applied by the nut through the rotating shaft assembly.

8. The straight-tube actuator as described in claim 4, characterized in that, The base is provided with a radial support bearing, which is sleeved on the outer periphery of the rotating shaft connector and disposed in the through hole of the partition to limit the radial displacement of the rotating shaft connector relative to the base and maintain the rotational coaxiality of the rotating shaft assembly.

9. The straight-tube actuator as described in claim 3, characterized in that, A reduction mechanism is provided between the motor and the rotating shaft assembly, and the reduction mechanism includes: A chassis, the inner circumference of which forms an internal gear ring; and A planetary gear assembly is disposed within the chassis, the planetary gear assembly comprising: A sun gear assembly includes a carrier and a sun gear formed on the carrier, the sun gear assembly being drively connected to the output shaft of the motor, and a plurality of locating pins being provided on one side of the carrier; A plurality of planetary gears are arranged around the sun gear and mesh with the sun gear and the internal gear ring; A plurality of planetary gear pins, each planetary gear pin being fixedly mounted on the body of the fastening part and providing rotational support for a corresponding planetary gear; and A support pad is provided on the side of the plurality of planetary gears near the motor.

10. The straight-tube actuator as described in claim 9, characterized in that, The fastening part is located on the side of the plurality of planetary gears away from the motor; a plurality of fixing holes are formed on the body of the fastening part at circumferential intervals, and a planetary gear shaft pin is respectively provided for each of the plurality of fixing holes, so that the plurality of planetary gears are supported by each planetary gear shaft pin and clamped between the support pad and the fastening part.

11. The straight-tube actuator as described in claim 10, characterized in that: It also includes a motor adapter, disposed between the motor and the reduction mechanism; the motor adapter has an axially penetrating central hole and a plurality of positioning holes spaced circumferentially along the outer edge of the central hole, wherein the central hole is for the output shaft of the motor to pass through and be fixedly connected, and the plurality of positioning holes correspond to a plurality of positioning pins disposed on one side of the sun gear component, so that each positioning pin can be inserted into the corresponding positioning hole, so that the sun gear component is circumferentially positioned and coaxially aligned with the motor adapter.

12. The straight-tube actuator as described in claim 3, characterized in that, A base groove is formed on at least one side of the partition; The axial support structure includes: At least one bushing is fitted onto the rotating shaft connector and is rotatable together with it. The bushing has a flange portion with a flange face facing the partition portion, and the flange face forms a flange groove; and At least one retainer includes a frame body forming an opening through which the rotating shaft connector passes, and having a plurality of seat holes circumferentially provided in the opening, each of the plurality of seat holes accommodating a steel ball, such that each steel ball partially protrudes from both sides of the frame body. The retainer is disposed between the bushing and the partition, so that the plurality of steel balls make rolling contact with the flange groove and the base groove respectively, so as to support and transmit the axial load applied by the nut through the rotating shaft assembly.

13. The straight-tube actuator as described in claim 12, characterized in that, Also includes: A front cover, which has a plurality of front cover holes; Multiple guide rods, one end of each guide rod is inserted through a corresponding front cover hole, and the other end is fixed to one side of the base; A front-end housing is fitted over the nut and has a plurality of guide rod grooves formed on its inner circumference, each groove allowing a corresponding guide rod to pass through; and A motor mounting bracket is disposed between the motor and the reduction mechanism. The motor mounting bracket is used to support and position the motor, and is fixedly connected to the chassis and the base via a plurality of fasteners. The motor is exposed outside the front cover, the front housing, and the base.

14. The straight-tube actuator as described in claim 13, characterized in that, The inner circumference of the front housing is formed with at least one keyway, and the outer circumference of the nut is provided with a key portion. The key portion is embedded in the keyway to restrict the rotational freedom of the nut relative to the front housing and guide the nut to move in the axial direction.

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