Linear actuator

Abstract

The utility model discloses a linear driver, which comprises a cylindrical shell, a motor coil and a motor magnet of a driving motor arranged in the shell, and a reverse circulation ball screw system, the periphery of the motor coil is fixed on the inner wall of the shell and is connected with a power supply and a signal line; the motor magnet is inserted into the motor coil; the reverse circulation ball screw system comprises a ball screw, a ball nut and balls arranged between the ball screw and the ball nut. The periphery of the ball nut is fixed on the inner wall of the motor magnet; the ball screw is installed in the ball nut, and the front end of the ball screw extends out of the shell and is provided with a fixing base. The miniature reverse circulation ball screw system and the driving motor are integrated, so that the overall linear driving size is greatly reduced, the power density is improved, and the miniature reverse circulation ball screw driving device is suitable for high-precision operation in the field of precision robots and mechanical arms.

Description

Technical Field

[0001] The utility model relates to a linear actuator, specifically a linear actuator driven by a micro reverse circulating ball screw, belonging to the technical field of robots. Background Art

[0002] Manipulators are often used to replace human hands to achieve operations such as grasping and operating, with the characteristics of precision and flexibility, and have broad application prospects in the fields of medical treatment, chemical industry, agricultural machinery, etc.

[0003] Currently, methods such as tendon rope drive, gear drive, and trapezoidal screw are often used to achieve the movement of the manipulator.

[0004] However, the tendon rope drive has the following technical defects: due to the stretching and elasticity of the rope, certain errors will be generated, affecting the accuracy; the friction is large, and the rope needs to be frequently maintained and replaced; the rigidity is poor, not suitable for high-load applications; it is easily worn and needs to be frequently maintained and replaced.

[0005] The gear drive has the following technical defects: gaps and vibrations may occur during the transmission process, affecting the smoothness and accuracy; the noise is large during high-speed operation; due to the wear of the gears, regular maintenance and replacement are required.

[0006] The trapezoidal screw has the following technical defects: adopting sliding friction, the efficiency is low, and it is easy to heat under high load; the gap is large, affecting the accuracy; due to the large friction, it wears quickly and needs to be frequently maintained and replaced.

[0007] Therefore, it is urgent to research and develop a new linear drive device to meet the higher usage requirements of the manipulator. Summary of the Invention

[0008] In view of the above existing technical problems, the utility model provides a linear actuator, which integrates a micro reverse self-circulating ball screw and a drive motor into one body to achieve the technical purpose of greatly reducing the overall linear drive size and improving the power density.

[0009] To achieve the above technical purpose, the utility model provides a linear actuator, including a cylindrical outer shell, the motor coil and the motor magnet of the drive motor arranged inside the outer shell, and a reverse circulating ball screw system;

[0010] The outer periphery of the motor coil is fixed on the inner wall of the outer shell and is connected with a power supply and a signal line; the motor magnet is inserted into the motor coil;

[0011] The reverse-circulation ball screw system includes a ball screw, a ball nut, and balls disposed between the ball screw and the ball nut; the outer periphery of the ball nut is fixed to the inner wall of the motor magnet; the ball screw is installed in the ball nut, and its front end extends out of the housing and is equipped with a fixed seat.

[0012] In the above technical solution, the present utility model realizes the driving function through a micro reverse-circulation ball screw system, and has the following technical advantages:

[0013] 1. Compared with tendon rope drive, the linear driver of the present utility model has higher positioning accuracy and repeatability; the rolling friction coefficient is lower, and the efficiency is higher; it has good rigidity, can withstand larger loads; has less wear, long service life, and low maintenance cost.

[0014] 2. Compared with gear drive: The linear driver of the present utility model is smoother during transmission, has higher positioning accuracy and repeatability; runs with lower noise; has a lower maintenance frequency and long service life.

[0015] 3. Compared with trapezoidal screws: The linear driver of the present utility model has a lower rolling friction coefficient and high transmission efficiency. It has high precision, small return clearance, and is suitable for high-precision positioning; has a long service life and low maintenance cost.

[0016] In the present utility model, further, spiral nut raceways are uniformly arranged on the inner wall of the ball nut; a reverse-circulation raceway is arranged on the outer periphery of the rear end of the ball screw; the reverse-circulation raceway cooperates with the nut raceway to form a ball passage for the balls to roll and run.

[0017] Driven by the drive motor, the ball nut makes a circumferential rotational movement along with the motor magnet, thereby driving the balls to roll and run in the ball passage, and further driving the ball screw to make an axial linear movement along the ball nut.

[0018] In the above technical solution, the reverse-circulation ball screw system makes the reverse-circulation raceway on the ball screw, and its operating principle is similar to that of the reverse-circulation roller screw. When the drive motor directly drives the ball nut through the motor magnet, the circumferential rotational movement of the ball nut can be converted into the axial linear movement of the ball screw, thereby realizing the function of linear drive. Moreover, the reverse-circulation ball screw system has a simple structure, is easy to process, has a small volume, and high efficiency, and is particularly suitable for application scenarios such as humanoid robots where the installation space is limited but long life and continuous operation are required.

[0019] Furthermore, in the present utility model, the reverse circulation raceway includes a load-carrying raceway and a circulation groove; the load-carrying raceway is annular, and a plurality of load-carrying raceways are evenly arranged on the outer periphery of the rear end of the ball screw, and the distance between two adjacent load-carrying raceways is equal to the pitch of the nut raceway; the circulation groove is a transition surface arranged in the load-carrying raceway, the depth of the middle part thereof is greater than the depth of the corresponding load-carrying raceway, and a plurality of circulation grooves are arranged in a spiral shape in the corresponding load-carrying raceways.

[0020] Further, the reverse circulation ball screw system of the present utility model further includes a support bearing; the outer periphery of the support bearing is fixed on the inner wall of the housing, located behind the motor coil and the motor magnet, and sleeved on the outer periphery of the rear end of the ball nut.

[0021] Furthermore, the reverse circulation ball screw system of the present utility model further includes a locking nut; an external thread is provided on the outer periphery of the rear end of the ball nut; the locking nut is fixed at the rear end of the support bearing and installed on the outer periphery of the rear end of the ball nut.

[0022] Further, the reverse circulation ball screw system of the present utility model further includes a fixed bearing; the outer periphery of the fixed bearing is fixed on the inner wall of the housing, located in front of the motor coil and the motor magnet, and sleeved on the outer periphery of the front end of the ball nut.

[0023] Further, a front end cover and a rear end cover are respectively installed at the front and rear ends of the cylindrical housing.

[0024] Furthermore, the present utility model further includes an encoder placed inside the housing; the encoder is installed on the inner wall of the rear end cover and connected with a power supply and signal lines.

[0025] In summary, the linear actuator provided by the present utility model integrates the micro reverse circulation ball screw system and the driving motor into one body, which not only greatly reduces the overall linear drive size, but also improves the power density of the linear drive, and is applicable to high-precision operations in the fields of precision robots and robotic arms.

[0026] Compared with the prior art, the linear actuator of the present utility model has the following technical advantages:

[0027] A. By adopting the combination of the driving motor and the reverse circulation ball screw system, the rotor part of the motor is installed on the periphery of the ball nut of the reverse circulation ball screw system, so that the ball nut can rotate relative to the housing. When the driving motor directly drives the ball nut, the circumferential rotational motion of the ball nut can be converted into the axial linear motion of the ball screw, thereby realizing the linear drive function for other components.

[0028] B. The reverse-circulation ball screw system is configured such that a helical nut raceway is provided on the inner wall of the ball nut, and a reverse-circulation raceway is provided on the outer periphery of the ball screw. The reverse-circulation raceway and the nut raceway cooperate with each other to form a ball passage for the balls to roll, enabling the balls to achieve circulating rotation within the ball nut by relying on the reverse-circulation raceway, without the need to use a circulator conventionally provided on the ball nut to achieve this scenario.

[0029] C. Since the reverse-circulation ball screw system has advantages such as low friction, low noise, less wear, long service life, and low maintenance cost during operation, the linear actuator has high precision, high efficiency, and high load capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0031] Figure 1 is a schematic structural diagram of the present invention;

[0032] Figure 2 is Figure 1 a partial enlarged schematic view of part A in

[0033] Figure 3 is a schematic structural diagram of the ball screw in the present invention;

[0034] Figure 4 is Figure 3 a partial enlarged schematic view of part B in

[0035] In the figure: 11, fixed seat; 12, ball screw; 13, outer shell; 14, front end cover; 15, fixed bearing; 16, motor coil; 17, motor magnet; 18, power supply and signal line; 19, ball nut; 110, support bearing; 111, locking nut; 112, encoder; 113, rear end cover; 117, load-bearing raceway; 118, circulation groove; 119, nut raceway; 120, circulation start point; 121, circulation end point. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] To make the objectives, technical solutions, and advantages of the present utility model clearer, the following will clearly and completely describe the technical solutions of the present utility model in conjunction with the embodiments of the present utility model. Obviously, the described embodiments are some, but not all, of the embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts fall within the scope of protection of the present utility model.

[0037] In the description of this application, terms such as "connection" or "coupling" do not limit to physical or mechanical connections, but may include electrical connections, whether direct or indirect. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0038] In the description of this application, "upper", "lower", "left", "right", etc. are only used to represent relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0039] As Figure 1 shown, this embodiment provides a linear actuator, which includes a cylindrical outer shell 13, a motor coil 16 of a drive motor disposed inside the outer shell 13, a motor magnet 17 of the drive motor, and a reverse circulation ball screw system, which will be specifically introduced as follows.

[0040] The drive motor is used to provide power for the linear actuator of the present utility model, especially for the reverse circulation ball screw system. The outer periphery of the motor coil 16 is fixed on the inner wall of the outer shell 13 and is connected with a power supply and signal line 18 extending out of the outer shell 13. The motor magnet 17 is inserted into the motor coil 16. In specific implementation, the power supply and signal line 18 supplies power and transmits signals for the drive motor to ensure the energy and information transfer between the drive motor and the controller.

[0041] The reverse circulation ball screw system is used to achieve the linear drive function of the linear actuator of the present utility model, and includes a ball screw 12, a ball nut 19, and balls disposed between the ball screw 12 and the ball nut 19. Among them, the outer periphery of the ball nut 19 is fixed on the inner wall of the motor magnet 17. In specific implementation, the motor magnet 17 can be adhered to the outer periphery of the ball nut 19. The ball screw 12 is installed in the ball nut 19, and the front end extends out of the outer shell 13 and is installed with a fixing seat 11, and the fixing seat 11 is used to connect a manipulator or other actuating components.

[0042] As can be seen from the above technical solution, the rotor part of the driving motor, that is, the motor magnet 17, is installed on the periphery of the ball nut 19, so that the ball nut 19 is designed as the rotor part of the driving motor. The stator part of the driving motor, that is, the motor coil 16, is fixed on the inner wall of the housing 13, so as to provide driving power for the reverse circulation ball screw system.

[0043] As Figure 1 and Figure 2 shown, in the reverse circulation ball screw system, spiral nut raceways 119 are uniformly arranged on the inner wall of the ball nut 19; a reverse circulation raceway is arranged on the outer periphery of the rear end of the ball screw 12; and the reverse circulation raceway cooperates with the nut raceway 119 to form a ball channel for the balls to roll and run; the balls are arranged in the ball channel and can run back and forth in a cycle.

[0044] The motor coil 16 and the motor magnet 17 provide driving force for the reverse circulation ball screw system to ensure the operation execution of the entire linear actuator. Driven by the driving motor, the ball nut 19 makes a circumferential rotational motion along with the motor magnet 17, so as to drive the balls to roll and run in the ball channel, and further drive the ball screw 12 to make an axial linear motion along the ball nut 19.

[0045] In specific implementation, the reverse circulation ball screw system adopts a unique combination design of a long nut and a short screw, that is, the ball nut 19 is a long cylindrical shape different from the traditional design, which is convenient for designing the long nut as the motor rotor, and thus it is easy to realize an electromechanical integrated linear actuator. And different from the traditional ball screw structure with a circulator, the present utility model adopts a reverse circulation raceway without a circulator, and the reverse circulation raceway is made on the outer periphery of the rear end of the ball screw 12, which not only does not require a separate hole to install the circulator, but also improves the rigidity of the structure and avoids the error in the assembly of the connecting part.

[0046] As Figures 2 - 4 shown, in other implementation manners, the reverse circulation raceway includes a load-carrying raceway 117 and a circulation groove 118, which are introduced as follows.

[0047] The load-carrying raceway 117 is annular and multiple are provided. Multiple load-carrying raceways 117 are uniformly arranged on the outer periphery of the rear end of the ball screw 12, and the distance between adjacent two load-carrying raceways 117 is equal to the pitch of the nut raceway 119. And the number of the load-carrying raceways 117 can be adjusted according to the sizes of the ball screw 17 and the ball nut 19.

[0048] The loop groove 118 is a transition surface provided in the load-carrying raceway 117, and the depth of the middle part thereof is greater than the depth of the corresponding load-carrying raceway 117. A plurality of loop grooves 118 are arranged in a spiral shape in the corresponding load-carrying raceways 117 one by one. Since the plurality of loop grooves 118 are arranged in a spiral shape at a certain angle, mutual interference is avoided. Moreover, the number of the loop grooves 118 can be adjusted according to the sizes of the ball screw 17 and the ball nut 19.

[0049] As Figure 4 shown, the joints of the loop groove 118 and the corresponding load-carrying raceway 117 are a loop start point 120 and a loop end point 121 respectively. The balls in the load-carrying raceway 117 roll into the corresponding loop groove 118 from the loop start point 120, and then return to the corresponding load-carrying raceway 117 from the loop end point 121, realizing the cyclic operation of the balls in the ball nut 19.

[0050] In specific implementation, the ball nut 19 is equivalent to the rotor part of the driving motor. When making a circumferential rotational movement in the housing 13, multiple groups of balls 3 first run in the nut raceway 119 and the load-carrying raceway 117. When the work is completed, they return to the loop start point 120 and the loop end point 121 through the loop groove 118, thereby pushing the ball screw 12 to continue to make an axial linear movement, realizing an electromechanical integrated linear actuator.

[0051] As Figure 1 shown, in other embodiments, the reverse-circulation ball screw system further includes a support bearing 110; the outer periphery of the support bearing 110 is fixed on the inner wall of the housing 13, located behind the motor coil 16 and the motor magnet 17, and sleeved on the outer periphery of the rear end of the ball nut 19, thereby fixing the rear end position of the ball nut 19 and facilitating the ball nut 19 to make a rotational movement along the housing 13 under the drive of the driving motor.

[0052] As Figure 1 shown, in other embodiments, the reverse-circulation ball screw system further includes a lock nut 111; an external thread is provided on the outer periphery of the rear end of the ball nut 19; the lock nut 111 is fixed at the rear end of the support bearing 110 and installed on the outer periphery of the rear end of the ball nut 19, thereby locking the support bearing 110 to the rear end of the ball nut 19, playing a role in strengthening the support.

[0053] As Figure 1As shown, in other embodiments, the reverse circulation ball screw system further includes a fixed bearing 15; the outer periphery of the fixed bearing 15 is fixed on the inner wall of the housing 13, in front of the motor coil 16 and the motor magnet 17, and is sleeved on the outer periphery of the front end of the ball nut 19, so as to fix the front end position of the ball nut 19 and facilitate the ball nut 19 to rotate along the housing 13 under the drive of the driving motor.

[0054] As can be seen from the above technical solution, the ball screw 12, the ball nut 19, the support bearing 110, the fixed bearing 15, and the locking nut 111 installed in the linear actuator of the present invention form a reverse circulation ball screw system. The reverse ball screw system realizes precise and smooth linear motion through high-efficiency and low-friction transmission, and has the advantages of high precision, high efficiency, and long life, enabling the linear actuator to achieve high-precision linear motion.

[0055] As Figure 1 shown, in other embodiments, front end covers 14 and rear end covers 113 are respectively installed at the front and rear ends of the cylindrical housing 13, which play a role in dust prevention and sealing.

[0056] As Figure 1 shown, in other embodiments, the present invention further includes an encoder 112; the encoder 112 is placed inside the housing 13, installed on the inner wall of the rear end cover 113, and is connected with a power supply and signal line 18 extending out of the housing 13. Specifically, during implementation, the encoder 112 is used to monitor and feedback position data in real time, provide the position information of the ball nut 19 to the controller, and help the controller perform precise control, thereby forming a closed-loop feedback control.

[0057] In summary, the linear actuator of the present invention adopts an integrated design, fixes the motor coil 16 of the driving motor on the housing 13 to form an armature in the motor assembly, and installs the motor coil 16 of the driving motor on the outer periphery of the ball nut 19 of the reverse circulation ball screw system, so that the ball nut 19 can perform circumferential rotational motion relative to the housing 13. Since the ball screw 12 moves along the axial direction as the ball nut 19 rotates circumferentially, the reverse circulation ball screw system serves as the transmission part driven by the armature to drive other components installed on the fixed seat 11 at the front end of the ball screw 12. In addition, the linear actuator of the present invention further includes an encoder 112 for feedback position, and the encoder 112 provides the output shaft position information to the controller, so that the controller combines with the servo amplifier to operate the linear actuator in a closed-loop feedback control environment.

[0058] Moreover, the reverse-circulation ball screw system of the present utility model has significant advantages in terms of precision, efficiency, rigidity, lifespan, and noise control, and is suitable for applications requiring high precision, high load, and long lifespan. In contrast, tendon ropes are suitable for light-load and flexible-structure applications, but have poor precision and rigidity; gear drives are suitable for transmitting large torques, but are limited in terms of noise and precision; trapezoidal screws are suitable for applications requiring a self-locking function, but are less efficient and precise than ball screws 12.

[0059] Based on this, the linear actuator driven by the micro reverse-circulation ball screw of the present utility model has the following technical advantages: a. High precision and repeatability: It generally has higher positioning precision and repeatability; b. Low friction and high efficiency: Due to the low rolling friction coefficient of the reverse-circulation ball screw system, the linear actuator has high efficiency; c. High rigidity and load capacity: Since the reverse-circulation ball screw system has good rigidity, the linear actuator can withstand large loads; d. Long lifespan and low maintenance: Due to the small wear of the reverse-circulation ball screw system, the linear actuator has a long lifespan and low maintenance costs.

[0060] The technical solutions provided by the embodiments of the present utility model have been introduced in detail above. Specific examples are used in this article to elaborate on the principle and implementation manner of the present utility model. The description of the above embodiments is only used to help understand the method and its core idea of the present utility model; at the same time, for those of ordinary skill in the art, according to the idea of the present utility model, the technical solutions recorded in the foregoing embodiments can be modified, or some of the technical features can be equivalently replaced; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the idea and scope of the technical solutions of the embodiments of the present utility model.

Claims

1. A linear actuator, characterized in that, It includes a cylindrical housing, a motor coil and a motor magnet of a drive motor arranged inside the housing, and a reverse-circulation ball screw system; The outer periphery of the motor coil is fixed on the inner wall of the housing and is connected to a power supply and signal lines; The motor magnet is inserted into the motor coil; The reverse-circulation ball screw system includes a ball screw, a ball nut, and balls arranged between the ball screw and the ball nut; The outer periphery of the ball nut is fixed on the inner wall of the motor magnet; The ball screw is installed in the ball nut, and its front end extends out of the housing and is equipped with a fixed seat.

2. The linear actuator according to claim 1, characterized in that, The inner wall of the ball nut is evenly provided with a spiral nut raceway; The outer periphery of the rear end of the ball screw is provided with a reverse-circulation raceway; The reverse-circulation raceway cooperates with the nut raceway to form a ball channel for the balls to roll and run; Driven by the drive motor, the ball nut makes a circumferential rotational movement along with the motor magnet, thereby driving the balls to roll and run in the ball channel, and further driving the ball screw to make an axial linear movement along the ball nut.

3. The linear actuator according to claim 2, characterized in that, The reverse-circulation raceway includes a load-carrying raceway and a circulation groove; The load-carrying raceway is annular, and a plurality of load-carrying raceways are evenly arranged on the outer periphery of the rear end of the ball screw, and the distance between two adjacent load-carrying raceways is equal to the pitch of the nut raceway; The circulation groove is a transition surface arranged in the load-carrying raceway, the depth of the middle part thereof is greater than the depth of the corresponding load-carrying raceway, and a plurality of circulation grooves are arranged in a spiral shape in the corresponding load-carrying raceway.

4. A linear actuator according to claim 1 or 2 or 3, characterized in that, The reverse-circulation ball screw system further includes a support bearing; The outer periphery of the support bearing is fixed on the inner wall of the housing, located behind the motor coil and the motor magnet, and is sleeved on the outer periphery of the rear end of the ball nut.

5. A linear actuator according to claim 4, characterized in that, The reverse-circulation ball screw system further includes a lock nut; The outer periphery of the rear end of the ball nut is provided with an external thread; The lock nut is fixed at the rear end of the support bearing and is installed on the outer periphery of the rear end of the ball nut.

6. A linear actuator according to claim 1 or 2 or 3, characterized in that, The reverse-circulation ball screw system further includes a fixed bearing; The outer periphery of the fixed bearing is fixed on the inner wall of the housing, located in front of the motor coil and the motor magnet, and is sleeved on the outer periphery of the front end of the ball nut.

7. A linear actuator according to claim 1 or 2 or 3, characterized in that, The front and rear ends of the cylindrical housing are respectively installed with a front end cover and a rear end cover.

8. A linear actuator according to claim 7, characterized in that, It further includes an encoder placed inside the housing; The encoder is installed on the inner wall of the rear end cover and is connected to a power supply and signal lines.

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