Anti-rotation mechanism of linear joint counter-screw pair

Abstract

The utility model discloses a kind of anti-rotation mechanisms of linear joint's reverse screw pair, including the push rod anti-rotation mechanism being installed on front end cover, the push rod anti-rotation mechanism includes front, rear outer cover and several anti-rotation rollers;The center of front outer cover is provided with a front push rod perforation, and several front anti-rotation roller grooves are provided on the rear surface of front outer cover along the rear end orifice annular array of front push rod perforation;The center of rear outer cover is provided with a rear push rod perforation, and several rear anti-rotation roller grooves are provided on the front surface of rear outer cover along the front end orifice of rear push rod perforation;Each anti-rotation roller includes carrier roller and two bearings being installed in the both ends of the shaft body of carrier roller;Several anti-rotation rollers are placed in several rear anti-rotation roller grooves on rear outer cover, and front outer cover is combined on the front surface of rear outer cover, so that the carrier roller in each anti-rotation roller is rotatably located in carrier roller accommodating cavity, and so that two bearings in each anti-rotation roller are respectively fixed in corresponding bearing accommodating hole.The utility model can effectively limit push rod rotation.

Description

Technical Field

[0001] This utility model relates to an anti-rotation mechanism for a linear joint reverse lead screw pair. Background Technology

[0002] The problem of actuator rotation is a common technical issue in linear actuators, mainly stemming from factors such as frictional transmission of the lead screw pair in the transmission system, torque imbalance, rotational torque caused by lateral forces or eccentric loads, and wear-induced anti-rotation failure. While existing actuator anti-rotation technologies each have their own characteristics, they still have significant shortcomings in terms of structural complexity, installation and maintenance difficulty, cost-effectiveness, high-speed impact conditions, and long-term wear resistance.

[0003] I. Analysis of Linear Bearing Anti-Rotation Technology Linear bearings are a basic type of linear guiding mechanism, achieving low-friction motion through point contact between steel balls and a cylindrical shaft, but their anti-rotation design has limitations. Currently, there are three main types of anti-rotation structures: 1. Geometric Fitting Type: The outer circle of the bearing housing is machined into a non-circular structure to fit a correspondingly shaped mounting hole for anti-rotation. No additional parts are required, and the structure is simple and reliable. However, the non-circular housing needs to be custom-made, increasing manufacturing costs. The mounting hole requires high machining precision, and wear on the non-circular contact surface after long-term use can lead to anti-rotation failure.

[0004] 2. Mechanical limiting type: A positioning groove is set on the side of the bearing flange or housing, which cooperates with the mounting base protrusion or pin to prevent rotation. It has high installation flexibility, but the anti-rotation effect will be reduced by wear of the positioning pin or groove, and the edge of the positioning groove is prone to fatigue fracture.

[0005] 3. Composite structure: such as dual positioning structure, multiple anti-rotation methods are combined to limit rotational displacement, which can theoretically improve reliability. However, the increase in parts makes the system more complex, the assembly time is longer, the precision requirements of each component are high, and the manufacturing and installation costs are increased.

[0006] II. Analysis of Anti-rotation Technology for Linear Guides Linear guides have high load capacity and anti-rotation rigidity. They disperse torque through four rows of rolling steel balls and preload design, and resist installation deviations with automatic self-aligning function.

[0007] 1. High structural complexity: The slider contains multiple core components, and the four-row steel ball design increases the volume, system weight and space occupation, making manufacturing and assembly complex, increasing costs and failure risks.

[0008] 2. High installation accuracy requirements: The installation base surface has requirements for flatness, straightness, roughness and chamfer radius. The installation is time-consuming and costly, and requires professional equipment and technicians. It is not suitable for rapid assembly or low-cost scenarios.

[0009] 3. Wear and life issues are prominent: the contact point between the balls and the raceway is prone to fatigue and peeling, and excessive preload will shorten the life of the guide rail and affect the smoothness of movement.

[0010] 4. Difficult to maintain: Maintenance requires disassembling the entire system, and testing and adjusting the preload takes time and requires specialized tools and skills, increasing maintenance costs and difficulty.

[0011] III. Analysis of Anti-rotation Technology for Lead Screw Mechanisms The lead screw mechanism converts linear motion into linear motion via threaded transmission. Existing anti-rotation technologies include the mating of the nut and end cap, the guide sleeve and nut limiting mechanism, and anti-rotation key or pin structures.

[0012] 1. High structural complexity: Taking the anti-rotation device of the ball screw pair nut as an example, the increased number of parts and assembly complexity lead to increased costs. The nut limit mechanism requires precise matching, which increases manufacturing difficulty and cost.

[0013] 2. High installation and maintenance difficulty: The installation of the lead screw and support requires precision tools and complex procedures. Specifically, when fixing the support, a dial indicator is needed to correct the coaxiality error between its axis and the designed axis of the lead screw. The high precision requirement makes installation time-consuming and costly, unsuitable for rapid assembly or low-cost scenarios. In addition, the lead screw mechanism requires regular maintenance to check for changes in preload, increasing long-term operating costs.

[0014] The anti-rotation device of the lead screw mechanism has a significant deficiency in dynamic stability. The lead screw limiting structure of the actuator typically has an anti-rotation groove at the rear end of the lead screw extension end, combined with an elastic limiting sleeve to achieve circumferential positioning. The elastic limiting sleeve is made of a low-friction coefficient metal such as beryllium bronze or a self-lubricating engineering plastic. However, under high-frequency reciprocating vibration conditions, metal materials are prone to generating large noises, and self-lubricating materials are prone to uneven wear or fatigue fracture, leading to the failure of the anti-rotation function.

[0015] Heat dissipation is also a common defect in anti-rotation devices for lead screw mechanisms. While enclosed end cap anti-rotation structures can prevent impurities, they also hinder heat dissipation, leading to significant localized temperature rises. High temperatures accelerate material wear and deformation, reducing the anti-rotation effect and system lifespan. In addition, the keyway structure is prone to wear due to lateral forces over long-term use, gradually causing it to lose its anti-rotation function.

[0016] The linear joints of a humanoid robot provide tensile force like human muscles and consist of multiple linear actuators. These linear actuators typically use reverse ball screw pairs or reverse planetary roller screw pairs as transmission structures. A motor drives the nut to rotate, causing the screw to move axially, which in turn drives the push rod connected to the screw to extend or retract.

[0017] Because the push rod of the reverse lead screw is in a cantilevered state, the extended end of the linear actuator must provide necessary support and guidance for the push rod. The linear joints of humanoid robots require the actuator to have high-frequency response characteristics, while traditional guiding mechanisms are difficult to meet the comprehensive requirements of low frictional resistance, quiet operation, and shock resistance under high-speed conditions. Utility Model Content

[0018] The purpose of this invention is to overcome the defects of the prior art and provide an anti-rotation mechanism for a linear joint reverse lead screw pair. It can effectively limit the rotation of the push rod, ensure that the push rod can only perform axial extension and retraction, and also enhance the structural rigidity of the push rod and improve its resistance to lateral impact.

[0019] The purpose of this utility model is achieved as follows: an anti-rotation mechanism for a linear joint reverse lead screw assembly is installed on the front end cover of the linear joint. The linear joint includes a housing with the front end cover fixed at the front end, and a motor, a reverse lead screw assembly, and a bearing assembly disposed within the housing. One end of the lead screw of the reverse lead screw assembly is connected to a push rod, which extends out of the housing after passing through a push rod through-hole in the center of the front end cover, providing linear motion power to the outside. The motor provides rotational power to the nut of the reverse lead screw assembly, and the nut of the reverse lead screw assembly and the rotor of the motor are rotatably connected to the inner wall of the housing through the bearing assembly. The anti-rotation mechanism includes a front outer cover, a rear outer cover, and several anti-rotation rollers; wherein, The front outer cover has several connecting holes evenly distributed around its edge, corresponding one-to-one with several mounting holes on the front end cover; a front push rod through hole is opened in the center of the front outer cover, and several front anti-rotation roller grooves are arranged in a ring array along the rear end opening of the front push rod through hole on the rear surface of the front outer cover. Each front anti-rotation roller groove includes a front idler roller groove with an arc cross-section and two front bearing grooves with a semi-circular cross-section located at the two ends of the front idler roller groove, which correspond one-to-one; the front idler roller groove passes through the front push rod through hole. The rear outer cover has several connecting holes evenly distributed around its edge, corresponding one-to-one with several mounting holes on the front outer cover; the center of the rear outer cover has a rear push rod through hole that is adapted to and coaxial with the front push rod through hole on the front outer cover, and several rear anti-rotation roller grooves corresponding one-to-one with several front anti-rotation roller grooves on the front outer cover are formed along the front opening of the rear push rod through hole on the front surface of the rear outer cover; each rear anti-rotation roller groove includes a rear idler roller groove with an arc-shaped cross-section and two rear bearing grooves with a semi-circular cross-section located at both ends of the rear idler roller groove; the rear idler roller groove passes through the rear push rod through hole; each rear idler roller groove and its corresponding front idler roller groove together form a semi-circular idler roller receiving cavity, and each rear bearing groove and its corresponding front bearing groove together form a fully circular bearing receiving hole. Each of the anti-rotation rollers includes a bearingless idler roller and two small bearings that are installed at both ends of the shaft of the idler roller in a one-to-one correspondence; the idler roller is cylindrical and the outer diameter of the idler roller is larger than the outer diameter of the small bearing and smaller than the inner diameter of the idler roller receiving cavity, and the outer diameter of the small bearing is tightly fitted with the diameter of the bearing receiving hole; Several anti-rotation rollers are placed one-to-one in several rear anti-rotation roller grooves on the rear outer cover, and the front outer cover is placed on the front surface of the rear outer cover, so that the idler roller in each anti-rotation roller is rotatably located in the idler roller receiving cavity, and a part of the idler roller protrudes from the front push rod through hole and the rear push rod through hole, and the two small bearings in each anti-rotation roller are fixed in the corresponding bearing receiving hole. The rear outer cover and the front outer cover are sequentially disposed on the front surface of the front end cover and then fixed together to the front end of the housing by a number of screws. The push rod passes through the push rod through hole of the front end cover, the rear push rod through hole of the rear outer cover and the front push rod through hole of the front outer cover in sequence and then extends out of the housing. The generatrix of the idler rollers of the anti-rotation rollers are all in contact with the outer surface of the push rod.

[0020] In the aforementioned anti-rotation mechanism of the linear joint reverse lead screw pair, the cross-section of the push rod is a regular polygon with an even number of sides; the number of anti-rotation rollers is half the number of sides of the cross-section of the push rod.

[0021] In the aforementioned anti-rotation mechanism of the linear joint reverse lead screw pair, the idler roller is made of bearing steel.

[0022] In the aforementioned anti-rotation mechanism of the linear joint reverse lead screw pair, the small bearing is a needle roller bearing.

[0023] The anti-rotation mechanism of the linear joint reverse lead screw pair of this utility model has the following characteristics: 1. By using anti-rotation rollers and the rolling friction of the push rod, the frictional resistance during the axial extension and retraction of the push rod is significantly reduced, and the dynamic stability of the product in high-speed reciprocating or vibration environments is significantly improved. In addition, the use of high-precision idler rollers and bearings improves the positioning accuracy and repeatability of the push rod. It can also eliminate the gap between the push rod through hole in the front cover and the push rod, further improving the accuracy of the product during operation.

[0024] 2. Integrating the anti-rotation function into the transmission components not only reduces the number of parts compared to the ball spline design, but also improves system reliability and simplifies the installation process.

[0025] 3. The adoption of built-in anti-rotation rollers provides effective anti-rotation functionality without increasing radial dimensions. This not only saves space but also creates conditions for the miniaturization and compact design of linear joints, meeting the requirements of lightweight and compact structure for humanoid robots' linear joints.

[0026] 4. It adopts a separately detachable anti-rotation mechanism. Through standardized parts design, both the needle roller bearing and the idler roller can be modified from standard models, which significantly reduces the difficulty and cost of manufacturing and maintenance, and at the same time facilitates users to carry out regular inspection and maintenance.

[0027] 5. The push rod adopts a regular octagonal prism and is supported by four-sided rollers, which effectively restricts the rotation of the push rod, ensuring that the push rod can only perform axial extension and contraction. This also enhances the structural rigidity of the push rod and improves its resistance to lateral impact. In addition, the rollers made of bearing steel can effectively conduct heat to the housing, thereby improving the heat dissipation inside the reverse-type lead screw pair mechanism, extending its service life and maintaining stable performance. Attached Figure Description

[0028] Figure 1 This is an axial cross-sectional view of the anti-rotation mechanism of the linear joint reverse lead screw pair of this utility model. Figure 2 This is a perspective view of the front outer cover in the anti-rotation mechanism of this utility model; Figure 3 This is a perspective view of the rear outer cover in the anti-rotation mechanism of this utility model; Figure 4 This is a schematic diagram of the anti-rotation roller in the anti-rotation mechanism of this utility model; Figure 4a This is an axial cross-sectional view of the anti-rotation roller in the anti-rotation mechanism of this utility model; Figure 5 This is a perspective view of the anti-rotation roller installed on the front outer cover in the anti-rotation mechanism of this utility model; Figure 6 This is a perspective view of the anti-rotation rollers installed on the front and rear outer covers in the anti-rotation mechanism of this utility model; Figure 7 This is a perspective view of the push rod installed on the anti-rotation mechanism in the anti-rotation mechanism of this utility model. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings.

[0030] Please see Figures 1 to 7The anti-rotation mechanism of the linear joint reverse lead screw pair of this utility model is installed on the front end cover 10 of the linear joint. The linear joint includes a housing 1 with the front end cover 10 fixed at the front end, and a motor 2, a reverse lead screw pair assembly 3, and a bearing assembly 4 disposed in the housing 1. One end of the lead screw of the reverse lead screw pair assembly 3 is connected to a push rod 30. The cross-section of the push rod 30 is a regular polygon with an even number of sides, preferably a regular octagon. The push rod 30 passes through the push rod through hole in the center of the front end cover 10 and extends out of the housing 1 to provide linear motion power to the outside. The motor 2 provides rotational power to the nut of the reverse lead screw pair assembly 3. The nut of the reverse lead screw pair assembly 3 and the rotor of the motor 2 are rotatably connected to the inner wall of the housing 1 through the bearing assembly 4.

[0031] The anti-rotation mechanism of the linear joint reverse lead screw assembly of this utility model includes a front outer cover 5, a rear outer cover 6, and four anti-rotation rollers 7; wherein, The front outer cover 5 has eight connecting holes evenly distributed around its edge, corresponding one-to-one with the mounting holes on the front cover 10; a front push rod through hole 50 is opened in the center of the front outer cover 5, and four front anti-rotation roller grooves are arranged in a ring array along the rear end opening of the front push rod through hole 50 on the rear surface of the front outer cover 1. Each front anti-rotation roller groove includes a front idler roller groove 51 with an arc cross-section and two front bearing grooves 52 located at the two ends of the front idler roller groove 51 with a semi-circular cross-section; the front idler roller groove 51 passes through the front push rod through hole 50. The rear outer cover 6 has eight connecting holes evenly distributed around its edge, corresponding to the eight mounting holes on the front cover 10. The center of the rear outer cover 6 has a rear push rod through hole 60 that is adapted to and coaxial with the front push rod through hole 50 on the front outer cover 5. On the front surface of the rear outer cover 6, along the front opening of the rear push rod through hole 60, four rear anti-rotation roller grooves are formed, corresponding to the four front anti-rotation roller grooves on the front outer cover 5. Each rear anti-rotation roller groove includes a rear idler roller groove 61 with an arc-shaped cross-section and two rear bearing grooves 62 located at both ends of the rear idler roller groove 61 with a semi-circular cross-section. The rear idler roller groove 61 passes through the rear push rod through hole 60. Each rear idler roller groove 61 and the corresponding front idler roller groove 51 together form a semi-circular idler roller receiving cavity. Each rear bearing groove 62 and the corresponding front bearing groove 52 together form a fully circular bearing receiving hole. Each anti-rotation roller 7 includes a bearingless idler roller 71 and two small bearings 72 installed at both ends of the shaft of the idler roller 71 in a one-to-one correspondence; the outer diameter of the idler roller 71 is larger than the outer diameter of the small bearing 72 and smaller than the inner diameter of the idler roller receiving cavity, and the outer diameter of the small bearing 72 is tightly fitted with the diameter of the bearing receiving hole; the idler roller 71 is made of bearing steel; the small bearing 72 is a needle roller bearing.

[0032] Four anti-rotation rollers 7 are placed one-to-one in the four rear anti-rotation roller grooves on the rear outer cover 6, and the front outer cover 5 is closed on the front surface of the rear outer cover 6, so that the idler roller 71 in each anti-rotation roller 7 is rotatably located in the idler roller receiving cavity, and a part of the idler roller 71 protrudes from the front push rod through hole 50 and the rear push rod through hole 60, and the two small bearings 72 in each anti-rotation roller are fixed in the corresponding bearing receiving hole, and the idler roller 71 can rotate around the two small bearings 72.

[0033] The rear outer cover 6 and the front outer cover 5 are sequentially disposed on the front surface of the front cover 10 and then fixed together to the front end of the housing 1 by eight screws. The push rod 30 passes through the push rod through hole of the front cover 10, the rear push rod through hole 60 of the rear outer cover 6 and the front push rod through hole 50 of the front outer cover 5 and then extends out of the housing 1, so that the generatrix of the four anti-rotation rollers 71 contact the outer side of the push rod 30.

[0034] By setting the anti-rotation mechanism of the linear joint reverse lead screw pair of this utility model on the front end cover of the linear joint, the following effects can be achieved: Reduced friction and improved precision: By replacing sliding friction with rolling friction between the anti-rotation roller 7 and the push rod 30 (compared to sliding friction guide sleeves), the frictional resistance during axial extension and retraction of the push rod 30 is significantly reduced. Furthermore, the use of high-precision idler rollers 71 and small bearings 72 improves the positioning accuracy and repeatability of the push rod 30. Optimizing sliding friction into rolling friction significantly improves the dynamic stability of the linear joint under high-speed reciprocating or vibration environments. In addition, the gap between the push rod perforation in the front cover 10 and the push rod 30 is eliminated, further enhancing the precision during product operation.

[0035] The anti-rotation structure design is optimized, and the anti-rotation function is integrated into the transmission components. Compared with the ball spline design, this not only reduces the number of parts, but also improves system reliability and simplifies the installation process.

[0036] Space optimization and built-in design: The built-in anti-rotation rollers provide effective anti-rotation functionality without increasing radial dimensions. This not only saves space but also enables miniaturization and compact design of the device, meeting the requirements for lightweight and compact linear joints in humanoid robots.

[0037] Manufacturing and maintenance convenience: The anti-rotation mechanism is designed to be detachable. Through the standardized parts design, both the needle roller bearing and the idler roller can be modified from standard models, which significantly reduces the difficulty and cost of manufacturing and maintenance, and at the same time facilitates users to carry out regular inspection and maintenance.

[0038] Dynamic stability and heat dissipation improvements: The push rod 30 adopts a regular octagonal prism and is supported by four-sided rollers, which effectively restricts the rotation of the push rod 30, ensuring that the push rod 30 can only perform axial extension and contraction. This also enhances the structural rigidity of the push rod 30 and improves its resistance to lateral impacts. In addition, the rollers 71, made of bearing steel, can effectively conduct heat to the housing 1, thereby improving the heat dissipation inside the reverse-type lead screw pair mechanism 3, extending its service life and maintaining stable performance.

[0039] The above embodiments are for illustrative purposes only and are not intended to limit the present invention. Those skilled in the art can make various changes or modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should also fall within the scope of the present invention and should be defined by the claims.

Claims

1. An anti-rotation mechanism for a linear joint reverse lead screw assembly, mounted on the front end cover of a linear joint, the linear joint comprising a housing with the front end cover fixed at the front end, and a motor, a reverse lead screw assembly, and a bearing assembly disposed within the housing; one end of the lead screw of the reverse lead screw assembly is connected to a push rod, the push rod passing through a push rod through-hole in the center of the front end cover and extending out of the housing to provide linear motion power to the outside; the motor provides rotational power to the nut of the reverse lead screw assembly, and the nut of the reverse lead screw assembly and the rotor of the motor are rotatably connected to the inner wall of the housing through the bearing assembly; the anti-rotation mechanism comprises a front outer cover, a rear outer cover, and a plurality of anti-rotation rollers; characterized in that, The front outer cover has several connecting holes evenly distributed around its edge, corresponding one-to-one with several mounting holes on the front end cover; a front push rod through hole is opened in the center of the front outer cover, and several front anti-rotation roller grooves are arranged in a ring array along the rear end opening of the front push rod through hole on the rear surface of the front outer cover. Each front anti-rotation roller groove includes a front idler roller groove with an arc cross-section and two front bearing grooves with a semi-circular cross-section located at the two ends of the front idler roller groove, which correspond one-to-one; the front idler roller groove passes through the front push rod through hole. The rear outer cover has several connecting holes evenly distributed around its edge, corresponding one-to-one with several mounting holes on the front outer cover; the center of the rear outer cover has a rear push rod through hole that is adapted to and coaxial with the front push rod through hole on the front outer cover, and several rear anti-rotation roller grooves corresponding one-to-one with several front anti-rotation roller grooves on the front outer cover are formed along the front opening of the rear push rod through hole on the front surface of the rear outer cover; each rear anti-rotation roller groove includes a rear idler roller groove with an arc-shaped cross-section and two rear bearing grooves with a semi-circular cross-section located at both ends of the rear idler roller groove; the rear idler roller groove passes through the rear push rod through hole; each rear idler roller groove and its corresponding front idler roller groove together form a semi-circular idler roller receiving cavity, and each rear bearing groove and its corresponding front bearing groove together form a fully circular bearing receiving hole. Each of the anti-rotation rollers includes a bearingless idler roller and two small bearings that are installed at both ends of the shaft of the idler roller in a one-to-one correspondence; the idler roller is cylindrical and the outer diameter of the idler roller is larger than the outer diameter of the small bearing and smaller than the inner diameter of the idler roller receiving cavity, and the outer diameter of the small bearing is tightly fitted with the diameter of the bearing receiving hole; Several anti-rotation rollers are placed one-to-one in several rear anti-rotation roller grooves on the rear outer cover, and the front outer cover is placed on the front surface of the rear outer cover, so that the idler roller in each anti-rotation roller is rotatably located in the idler roller receiving cavity, and a part of the idler roller protrudes from the front push rod through hole and the rear push rod through hole, and the two small bearings in each anti-rotation roller are fixed in the corresponding bearing receiving hole. The rear outer cover and the front outer cover are sequentially disposed on the front surface of the front end cover and then fixed together to the front end of the housing by a number of screws. The push rod passes through the push rod through hole of the front end cover, the rear push rod through hole of the rear outer cover and the front push rod through hole of the front outer cover in sequence and then extends out of the housing. The generatrix of the idler rollers of the anti-rotation rollers are all in contact with the outer surface of the push rod.

2. The anti-rotation mechanism of the linear joint reverse lead screw pair according to claim 1, characterized in that, The push rod has a cross-section that is a regular polygon with an even number of sides; the number of anti-rotation rollers is half the number of sides of the push rod's cross-section.

3. The anti-rotation mechanism of the linear joint reverse lead screw pair according to claim 1, characterized in that, The idler roller is made of bearing steel.

4. The anti-rotation mechanism of the linear joint reverse lead screw pair according to claim 1, characterized in that, The small bearing is a needle roller bearing.

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