Linear servo joint for robot

Abstract

The invention discloses a linear servo joint for a robot. The linear servo joint comprises an end face worm and gear mechanism and a reverse planetary roller lead screw mechanism. The end face worm and gear mechanism comprises an end face worm gear and a worm which are in transmission connection, and the end face worm gear is driven by the worm to rotate. The reverse planetary roller lead screw mechanism comprises a lead screw, a nut, a plurality of rollers and a retainer, the rollers are limited on the lead screw in the height direction through the retainer, the lead screw is in transmission connection with the nut through the rollers, and the lead screw is driven by the nut through the rollers to move in the set direction. The end face worm gear is fixed to one axial end face of the nut, and the nut is driven by the worm to rotate through the worm gear. High-speed rotation of the motor can be converted into axial low-speed movement of the output shaft, a large and accurate transmission ratio and high bearing capacity and transmission efficiency can be guaranteed, and the high-rigidity requirement of a heavy-load robot is met while light weight and integration are achieved.

Description

Technical Field

[0001] The invention relates to the field of robot joints, and in particular to a linear servo joint for a robot. Background Art

[0002] With the rapid development of science and technology, artificial intelligence and robotics have made significant progress. Humanoid robots are one of the most promising and attractive branches in the field of artificial intelligence and robotics, aiming to create robots that look and behave like humans. Compared with wheeled and multi-legged robots, humanoid robots can navigate more complex terrains, have more flexible movement capabilities and speed change capabilities. Research and development in this field is not only for scientific breakthroughs, but also for the needs of practical applications, such as service industry, entertainment, popular science, medical assistance, disaster relief, etc.

[0003] These highly intelligent robots are gradually replacing traditional manual operations. For example, in many industrial environments, there are dangerous factors such as high temperature, high pressure, and toxic substances, which pose a serious threat to the health and safety of workers. However, the introduction of humanoid robots can completely avoid these problems. They can perform these tasks without any risk, ensuring the safety and continuity of the production process. They are widely used in all aspects of industrial production, greatly improving production efficiency, and effectively reducing the dependence of enterprises on labor, thereby reducing production costs.

[0004] As an important part of intelligent manufacturing, industrial robots play an important role in promoting the transformation and upgrading of the manufacturing industry and improving its competitiveness. Harmonic reducers are commonly used in the rear-end joints of industrial robots such as wrists, but they are difficult to meet the high rigidity requirements of heavy-duty robots such as cutting and grinding. High-speed ratio hypoid gear transmission is an effective way to solve the lack of rigidity of the rear-end joints of industrial robots. As a branch of hypoid gear transmission, end worm gear transmission has the advantages of large transmission ratio, strong load-bearing capacity and adjustable side clearance.

[0005] Roller screw pair transmission systems are widely used in humanoid robot joints. Roller screw pair transmission systems have the advantages of high transmission efficiency, high sensitivity, smooth transmission, low wear, long life and applicability to harsh working environments. They are particularly suitable for converting rotational motion into linear motion. Applying end worm gear transmission pairs and roller screw pair transmission systems to humanoid robot joints can significantly improve the operating performance of humanoid robots.

[0006] In the past, there have been many studies on robot joints based on planetary roller screw pairs. Patent CN220637966U proposes a rotary actuator for a humanoid robot joint based on a roller screw pair, which converts the input rotation of the screw into an output rotary motion of the nut without linear motion, but cannot provide a definite reduction ratio; Patent CN117245687 B proposes a flexible linear robot joint based on a planetary roller screw pair and a method of use, but its load-bearing capacity and stiffness are obviously insufficient and difficult to apply in practice; Patent CN 221455978 U proposes a humanoid robot joint with a simple structure and easy manufacture, but cannot achieve a self-locking function and has a relatively small transmission ratio.

[0007] Therefore, in response to this series of problems, the present invention proposes a linear servo joint for a robot that can convert the high-speed rotation of a motor into the axial low-speed motion of the output shaft, thereby ensuring a large and accurate transmission ratio, a higher load-bearing capacity and transmission efficiency, while being lightweight and integrated, and meeting the high rigidity requirements of heavy-load robots. Summary of the invention

[0008] In view of this, the purpose of the present invention is to overcome the defects in the prior art and provide a linear servo joint for a robot, which can realize the conversion of high-speed rotation of the motor into axial low-speed motion of the output shaft, ensure a large and accurate transmission ratio, high load-bearing capacity and transmission efficiency, while being lightweight and integrated, and meeting the high rigidity requirements of heavy-load robots.

[0009] The robot linear servo joint of the present invention comprises an end face worm gear mechanism and a reverse planetary roller screw mechanism;

[0010] The end face worm gear mechanism comprises an end face worm gear and a worm gear which are drivingly connected, and the end face worm gear is driven to rotate by the worm gear;

[0011] The reverse planetary roller screw mechanism comprises a screw, a nut, a plurality of rollers and a cage, wherein the plurality of rollers are limited on the screw in the height direction by the cage, the screw is drivingly connected to the nut through the plurality of rollers, and the screw is driven by the nut through the plurality of rollers to run in a predetermined direction;

[0012] The end face worm wheel is fixed to one of the axial end faces of the nut, and the nut is driven to rotate by the worm through the worm wheel.

[0013] Furthermore, it also includes a housing for assembling the end worm gear mechanism and the reverse planetary roller screw mechanism;

[0014] The nut is arranged in the middle of the housing through a bearing, the end face worm wheel is fixed on the top end of the nut, and the lead screw has a power output end extending downwardly out of the housing.

[0015] Furthermore, it also includes a driver and a frameless motor, wherein the driver is communicatively connected to the frameless motor, the rotor of the frameless motor is coaxially fixed with the worm, and the driving worm of the frameless motor controlled by the driver is transmission-connected to the end worm gear.

[0016] Furthermore, it also includes an encoder coaxially fixed with the worm, and the encoder is communicatively connected with the driver;

[0017] The installation position of the encoder is opposite to the installation position of the frameless motor in the axial direction of the worm.

[0018] Furthermore, it also includes a spoke-type tension and pressure sensor arranged at the power output end, the force-bearing end of the spoke-type tension and pressure sensor is coaxially fixed with the power output end, and the base of the spoke-type tension and pressure sensor is limited in height between the nut and the shell.

[0019] Furthermore, the front end and the rear end of the worm are respectively assembled on the housing via bearings.

[0020] Furthermore, the bearing arranged on the nut in the middle of the shell includes a needle roller bearing, and the needle roller bearing includes two needle roller bearings respectively arranged at the axial top end and the axial bottom end of the nut.

[0021] Furthermore, the radial outer wall of the nut extends outward to form a shoulder for assembling the two needle roller bearings, and the shoulder is located in the axial middle of the nut to separate and limit the two needle roller bearings in the axial direction of the nut.

[0022] Furthermore, the shell has an end face of a power output end with a stop hole, and the power output end is driven to run in a set direction through the stop hole, and the projection of the power output end on the axial direction of the screw is adapted to the stop hole.

[0023] Furthermore, the central axis of the end worm wheel and the central axis of the worm form an angle of 90°; the lead angle of the worm of the end worm wheel and worm mechanism is smaller than the equivalent friction angle between the meshing gear teeth.

[0024] The beneficial effects of the present invention are as follows: the linear servo joint for a robot disclosed in the present invention is designed by fixing the nut and the end worm gear coaxially and integrating them. When working, the rotation of the worm will drive the rotation of the end worm gear, and the nut of the planetary roller screw mechanism that forms an integral body with the end worm gear will also rotate accordingly. The nut drives the screw through multiple rollers to achieve linear motion. Through the above structure, the advantages of the large transmission ratio of the end worm gear mechanism and the efficiency and high precision of the reverse planetary roller screw mechanism are combined together, the comprehensive performance of the linear servo joint is improved, the bearing capacity and efficiency of the transmission device can be effectively improved, and the transmission ratio of the transmission can be effectively ensured; the high-speed rotation of the motor can be converted into the axial low-speed movement of the output shaft, and a large and accurate transmission ratio, high bearing capacity and transmission efficiency can be guaranteed. While being lightweight and integrated, it also meets the high rigidity requirements of heavy-duty robots. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0026] Figure 1 It is a structural schematic diagram of the present invention;

[0027] Figure 2 It is a schematic diagram of the main structure of the present invention;

[0028] Figure 3 For the present invention Figure 2 AA structural diagram;

[0029] Figure 4 For the present invention Figure 2 BB structural diagram;

[0030] Figure 5 It is a structural schematic diagram of the nut (with end face worm gear) of the reverse planetary roller screw;

[0031] Figure 6 It is a schematic diagram of the worm of the end face worm gear mechanism;

[0032] Figure 7 It is a structural schematic diagram of a screw in a reverse planetary roller screw mechanism;

[0033] Figure 8 It is a schematic diagram of the structure of the roller in the reverse planetary roller screw mechanism;

[0034] Fig. 9 is the reference coordinate system of the end worm gear transmission;

[0035] Fig.10 It is the spatial meshing coordinate system of the screw, roller and nut in the reverse planetary roller screw mechanism. DETAILED DESCRIPTION

[0036] Figure 1 It is a schematic diagram of the structure of the present invention. As shown in the figure, the linear servo joint for the robot in this embodiment includes an end worm gear mechanism and a reverse planetary roller screw mechanism;

[0037] The end face worm gear mechanism comprises an end face worm wheel 1 and a worm 2 which are connected in a transmission manner, and the end face worm wheel 1 is driven to rotate by the worm 2; the lead angle of the worm 2 of the end face worm gear mechanism is smaller than the equivalent friction angle between the meshing gear teeth, so that the end face worm gear mechanism has a reliable self-locking function; the central axis of the end face worm wheel 1 and the central axis of the worm 2 form an angle of 90°; the end face worm gear mechanism is a transmission device widely used in mechanical engineering, and is particularly suitable for occasions requiring a high transmission ratio and a strong load-bearing capacity. In addition, the end face worm gear mechanism is also known for its excellent rigidity, which enables the mechanism to maintain a high degree of stability during operation and is not prone to deformation or damage, thereby ensuring the accuracy and efficiency of the transmission;

[0038] The reverse planetary roller screw mechanism comprises a screw 3, a nut 4, a plurality of rollers 5 and a cage 6, wherein the plurality of rollers 5 are limited on the screw 3 in the height direction by the cage 6, the screw 3 is transmission-connected with the nut 4 through the plurality of rollers 5, and the screw 3 is driven by the nut 4 through the plurality of rollers 5 to run in a predetermined direction;

[0039] More specifically, the lead screw 3 passes through the nut 4, and the lead screw 3 and the nut 4 are connected by a plurality of rollers 5. The plurality of rollers 5 are limited on the lead screw 3 in the height direction by a retainer 6. The component that limits the retainer 6 is a retainer spring. The lead screw 3 has a retainer spring limiting groove for assembling the retainer spring. The reverse planetary roller screw mechanism has the advantages of high load capacity, high speed, large contact area, good wear resistance and high rigidity.

[0040] The end worm wheel 1 is fixed to one of the axial end faces of the nut 4, and the nut 4 is driven to rotate by the worm 2 through the end worm wheel. In this scheme, the nut 4 and the end worm wheel 1 are coaxially fixed and integrated. The axis of the worm 2 and the axis of the end worm wheel 1 are perpendicular to each other, and they rotate around their own axes respectively. The end worm wheel 1 and the nut 4 are fixedly connected as a whole. The upper surface of the nut 4 is the tooth surface of the end worm wheel 1, which is meshed with the worm 2; the internal thread of the nut 4 is meshed with the thread of the roller 5. The screw 3 passes through the retainer 6 and can rotate around its own axis. It should be understood that the retainer 6 is two arranged at the upper and lower ends of the roller 5. The two retainers 6 are respectively limited by the retaining spring, and the plate surface is perpendicular to the axis of the nut 4 and the axis of the screw 3. The roller 5 is multiple and surrounds the screw 3, and the retainer 6 is provided with multiple mounting holes, and the multiple mounting holes are evenly arranged around the axis of the retainer 6, which is used to install the roller 5. The multiple rollers 5 are evenly distributed around the screw 3 and supported by the retainer 6. In order to achieve a better contact state and realize higher load-bearing performance, the multiple rollers 5 are evenly arranged around the axis of the screw 3. The multiple rollers 5 can not only rotate around the screw 3, but also drive the screw 3 to move linearly. The transmission structure is stable and the transmission efficiency is high. The roller 5 is threaded with the screw 3, and the axis of the roller 5 is parallel to the axis of the screw 3 and the axis of the nut 4. When working, the rotation of the worm 2 will drive the rotation of the end worm wheel 1, and the nut 4 of the planetary roller screw mechanism that forms an integral body with the end worm wheel 1 will also rotate accordingly, and the nut 4 drives the screw 3 through multiple rollers 5 to achieve linear motion. Through the above structure, the advantages of the large transmission ratio of the end worm wheel mechanism and the high efficiency and precision of the reverse planetary roller screw mechanism are combined together, which improves the comprehensive performance of the linear servo joint, can effectively improve the bearing capacity and efficiency of the transmission device, and can effectively ensure the transmission ratio of the transmission.

[0041] In this embodiment, it also includes a housing for assembling the end worm gear mechanism and the reverse planetary roller screw mechanism; the nut 4 is arranged in the middle of the housing through a bearing, the end worm gear 1 is fixed at the top end of the nut 4, and the screw 3 has a power output end 14 extending downward from the housing.

[0042] like Figure 1-Figure 3 As shown, the housing includes a main housing 7 that accommodates the end worm gear mechanism and the reverse planetary roller screw mechanism. The main housing 7 is in a sleeve shape and circumferentially surrounds the reverse planetary roller screw mechanism. The end worm wheel 1 of the end worm gear mechanism and the top end of the nut 4 of the reverse planetary roller screw mechanism form a whole. The worm 2 is transmission-connected to the end worm wheel 1 at the top end of the main housing 7. The housing also includes an upper end cover 8 that closes the top end of the main housing 7 and a lower end cover 9 that closes the lower end of the main housing 7. The upper end cover 8 and the lower end cover 9 are assembled on the main housing 7 by bolts through corresponding flanges.

[0043] In this embodiment, it also includes a driver 10 and a frameless motor 11, wherein the driver 10 is communicatively connected with the frameless motor 11, the rotor of the frameless motor 11 is coaxially fixed with the worm 2, and the frameless motor 11 is driven by the driver 10 and is connected to the end worm gear 1; it also includes an encoder 12 coaxially fixed with the worm 2, and the encoder 12 is communicatively connected with the driver 10; the installation position of the encoder 12 is opposite to the installation position of the frameless motor 11 in the axial direction of the worm 2; it also includes a spoke type tension and pressure sensor 13 arranged at the power output end 14, the force-bearing end of the spoke type tension and pressure sensor 13 is coaxially fixed with the power output end 14, and the base of the spoke type tension and pressure sensor 13 is limited in height between the nut 4 and the housing.

[0044] The frameless motor 11 is used as a power source to provide power for the rotation of the worm 2. The rotor housing of the frameless motor 11 is coaxially arranged with the worm 2 in the mounting cavity of the housing. The stator of the frameless motor 11 is fixed at the top of the mounting cavity of the housing. The frameless motor 11 of this solution uses any one of the prior arts, which has a small size, high precision, and provides strong protection in harsh environments. By removing redundant components, the frameless motor 11 realizes an extremely compact and lightweight application design, which is just used in this solution.

[0045] The driver 10 is arranged near the end of the frameless motor 11 mounted on the worm 2. The driver 10 is used to control the speed output of the frameless motor 11. The driver 10 can be any one of the prior art, and a smaller one can be selected as much as possible, which is more in line with the lightweight integrated design of the present invention.

[0046] The encoder 12 is arranged away from the end of the worm 2 where the frameless motor 11 is mounted, and the thread on the worm 2 is close to the end where the encoder 12 is mounted on the worm 2, so the resolution is higher; the encoder 12 realizes the feedback of the stroke and position information of the lead screw 3 through the internal sensor, and completes the servo control of the movement amount and speed of the output end of the lead screw 3. It selects any one of the existing technologies, and selects the thin type as much as possible to realize the given function and meet the lightweight requirements;

[0047] In this solution, the driver 10 and the encoder 12 are respectively hidden in the side wall of the main housing 7, and the main housing 7 has a side cover that seals the two, so that the compactness of the structure, the accuracy of use and the protection are guaranteed.

[0048] The spoke type tension and pressure sensor 13 is used to measure the tension and pressure of the power output end 14 of the screw 3, and transmit the tension and pressure data of the power output end 14 of the screw 3 back to the control system. The spoke type tension and pressure sensor is selected from any one of the existing technologies to realize the detection and control of the load end force; it has the advantages of low height, high precision, good linearity, and strong resistance to eccentric loads and lateral forces;

[0049] In this solution, the spoke-type tension and pressure sensor 13 is limited at the power output end 14 of the screw 3, and the power output end 14 of the screw 3 also forms a support platform that cooperates with the inner side surface of the lower end cover 9 to limit the spoke-type tension and pressure sensor 13 in the inner cavity of the shell in the height direction.

[0050] The present solution also includes a computer or central processing unit in the prior art that is communicatively connected to the frameless motor 11, the driver 10, the encoder 12 and the spoke-type tension and pressure sensor 13, so as to form a closed-loop system of detection and control, which can accurately control the speed of the frameless motor 11, the position of the power output end 14 of the screw 3 and the torque of the power output end 14 of the screw 3, while also monitoring the operating status of the motor, such as current, voltage and temperature, and can effectively monitor its transmission smoothness and transmission accuracy. When an abnormal situation is detected, the power supply can be cut off in time to protect the motor from damage. The present solution solves the problems of low space utilization and unreliable self-locking in the existing linear servo joints, and also has the advantage of precise control of converting high speed into small stroke.

[0051] In this embodiment, the front and rear ends of the worm 2 are respectively mounted on the housing through bearings. More specifically, in this solution, the bearings used to mount the worm 2 in the inner cavity of the housing are tapered roller bearings; the two tapered roller bearings are respectively installed near the first end and the second end of the worm 2; the tapered roller bearing near the first end of the worm 2 is located on the inner side of the frameless motor 11, and the tapered roller bearing near the second end of the worm 2 is located on the inner side of the encoder 12. The inner side refers to the direction close to the axial middle of the worm 2, more specifically, as Figure 6 As shown, the worm 2 is in the shape of a stepped shaft, and the two tapered roller bearings and their corresponding sleeves are fixed at the axial ends of the worm 2, and the radial outer end faces of the two tapered roller bearings are respectively limited by the front side cover and the rear side cover.

[0052] In this embodiment, the bearing disposed in the middle of the housing of the nut 4 includes a needle bearing, and the needle bearing includes two needle bearings disposed at the axial top end and the axial bottom end of the nut 4 respectively; the radial outer wall of the nut 4 extends outward to form a shoulder 15 for assembling the two needle bearings, and the shoulder 15 is located in the middle of the axial direction of the nut 4 to separate and limit the two needle bearings in the axial direction of the nut 4. Figure 5As shown, there is a shaft shoulder for positioning the needle bearing in the middle of the nut 4, and the two bearings are respectively closed by the corresponding upper and lower end covers 9. More specifically, the upper needle bearing outer ring is limited by the top of the main housing 7, and the upper needle bearing inner ring is limited by the shaft shoulder located in the middle of the nut 4, so that the upper needle bearing is limited at the preset position of the nut 4; the lower needle bearing outer ring is limited by the top of the lower housing, and the lower needle bearing inner ring is limited by the shaft shoulder located in the middle of the nut 4, so that the lower needle bearing is limited at the preset position of the nut 4; the overall structure is more compact and the transmission is more reliable.

[0053] In this embodiment, the use of tapered roller bearings and needle bearings can further ensure the smoothness of the transmission of the entire device and increase the service life of the device.

[0054] In this embodiment, the end face of the housing having the power output end 14 is provided with a stop hole, and the power output end 14 is driven to run in a set direction through the stop hole, and the axial projection of the power output end 14 on the lead screw 3 is adapted to the stop hole. The meaning of this adaptation is that the shape of the power output end 14 of the lead screw 3 is the same as the shape of the stop hole, and there is a set matching gap between the two to meet the power output end 14 extending out or retracting into the stop hole; the stop hole is a special-shaped hole, which preferably has the function of preventing the lead screw 3 from rotating, so that the lead screw 3 can only move in a straight line. More specifically, the shape of the stop hole in this scheme is made into a waist-shaped hole, and the output end of the lead screw 3 is limited by the straight edge of the waist-shaped hole to prevent the rotation of the lead screw 3. The structure is simple and reliable, and it ensures that the motor input rotational motion is completely converted into the linear motion of the lead screw 3, preventing the transmission from being unstable, and ensuring the transmission accuracy of the integrated electric cylinder.

[0055] The core feature of the worm gear mechanism is its large transmission ratio, usually between 10 and 100, which means that the rotation speed of the output shaft can be significantly reduced, thereby achieving effective transmission and control of mechanical energy. When the worm rotates, its spiral groove pushes the teeth of the worm wheel, causing the worm wheel to rotate. Due to the large contact area between the spiral groove of the worm and the teeth of the worm wheel, this design not only improves the smoothness of the transmission, but also greatly enhances the load-bearing capacity of the mechanism. In the worm gear mechanism, due to the close fit of the worm wheel and the worm and the high strength of the material, the mechanism can maintain a high degree of stability during operation and is not prone to deformation or damage, thereby ensuring the accuracy and efficiency of the transmission.

[0056] In this embodiment, the tooth surface of the worm is an Archimedean spiral surface, and its generating line is two straight lines with different inclination angles. The lead angle of the worm is smaller than its friction angle, and it has a reliable self-locking function. For the end face worm wheel, the convex surface on the worm wheel and the worm tooth surface meshing therewith are called "i surface", and the concave surface on the worm wheel and the corresponding worm tooth surface are called "e surface". At the meshing point between the worm and the end face worm wheel, the relative motion velocity vector is perpendicular to the tooth surface normal vector, that is, the meshing equation is: Φ = n (m) ·v 12 (m) =0.

[0057] in:

[0058] v 12 (m) ——relative motion velocity vector in coordinate system Σm;

[0059] n (m) ——Normal vector of the tooth surface in coordinate system Σm.

[0060] Worm and end worm gear transmission ratio:

[0061] in:

[0062] ω1——angular velocity of the worm around its axis;

[0063] ω2——Angular velocity of the worm gear around its axis;

[0064] - the angle of rotation of the worm around its axis;

[0065] ——The angle of rotation of the worm gear around its axis.

[0066] Fig. 9 The figure shows the reference coordinate system of the end worm gear transmission, where the coordinate system Σ s (O s :x s ,y s ,z s ) is a fixed coordinate system established on the bevel worm, and the coordinate system Σ m (O m :x m ,y m ,z m ) is fixedly connected to the worm, and the coordinate origin is O s With O m Overlap, z s Axis and z m The axes coincide and are collinear with the worm rotation axis. φ1 is the instantaneous rotation angle of the worm. The conversion matrix between the coordinate systems of the end worm gear transmission is as follows:

[0067] Coordinate system Σs To coordinate system Σ m :

[0068]

[0069] Coordinate system Σ p To coordinate system Σ s :

[0070]

[0071] Coordinate system Σ p To coordinate system Σ n :

[0072]

[0073] Coordinate system Σ m To coordinate system Σ n :

[0074]

[0075] in:

[0076] ——The angle of rotation of the worm around its axis

[0077] - the angle of rotation of the worm gear around its axis;

[0078] A——center distance between worm wheel and worm;

[0079] E A =Z A +L w / 2

[0080] Z A ——worm gear offset installation distance;

[0081] L w - thread length;

[0082] E A —— Worm center to coordinate system Σ p The distance from the origin.

[0083] The intersection line between the worm tooth surface and the worm wheel tooth surface is the contact line, so it satisfies both the worm tooth surface equation and the meshing function. The contact line can be solved by the following set of equations:

[0084]

[0085] in:

[0086] u——the distance from any point on the worm production line to the coordinate origin;

[0087] ——angle of rotation of the worm helical motion;

[0088] r (m) ——In the coordinate system Σ m Lower tooth surface equation;

[0089] r x ,r y ,r z ——Components of the worm gear tooth surface equation in three directions;

[0090] i m , j m , k m ——Unit vectors in three directions of the worm tooth surface equation in the coordinate system Σm.

[0091] Furthermore, according to the gear meshing theory, at the meshing point between the worm and the end worm wheel, the relative motion velocity vector is perpendicular to the tooth surface normal vector, that is, the meshing equation is:

[0092] Φ=n (m) ·v 12 (m) =0

[0093] In the worm fixed coordinate system Σ m The contact line is solved by the simultaneous equations in the coordinate transformation matrix, and the contact line is transformed into the coordinate system Σ n The tooth surface equation on the upper side of the worm gear can be obtained for:

[0094]

[0095] in:

[0096] α i ——Inclination angle of tooth profile on the i-face of the end worm gear;

[0097] p i ——axial helical parameter of the worm i-face;

[0098] δ——the half-apex angle of the dividing cone;

[0099] i n , j n , k n ——In the coordinate system Σ n Unit vectors in three directions of the worm tooth surface equation.

[0100] The reverse planetary roller screw has spur gears on both ends of the screw, which keep meshing with the spur gears on both ends of the roller during movement; its nut is longer than that of the standard planetary roller screw, usually used for rotational input, driving the screw to achieve linear motion, and easy to integrate design;

[0101] During the operation of the reverse planetary roller screw, the threads of the screw, nut and roller must be in continuous meshing state at all times, which requires that the two meshing surfaces are always in tangential contact during the transmission process. However, in order to ensure that the planetary roller screw does not cause thermal deformation of the threads due to friction and heat rise during movement, resulting in jamming, and to ensure the smoothness of normal assembly, there should be a certain gap between the threads of each part.

[0102] The increase in the tooth profile angle of the reverse planetary roller screw will increase the contact stress on the screw side and the nut side, and the increase in the pitch will increase the unevenness of the contact stress distribution on both sides. In order to improve the load-bearing capacity of the reverse planetary roller screw, it should be considered to appropriately reduce the tooth profile angle and pitch. The number of threads of the roller can be appropriately increased, which will reduce the contact stress of the reverse planetary roller screw, but too many threads will aggravate the unevenness of the stress distribution, so it is necessary to select a reasonable number of threads during the design process;

[0103] Fig.10 is the spatial meshing coordinate system ox of the screw, roller and nut in the reverse planetary roller screw mechanism i y i z i (i=s, r, n represent the screw, roller and nut respectively), point P is any point on the helical surface of part i, then the parametric equation of the helical surface can be expressed as:

[0104] Q i =[r i cosθ i ,r i sinθ i ,F i (r pi ,θ i )]

[0105] r i is the thread pitch diameter;

[0106] r pi ,θ i is the position parameter of the helical surface in the coordinate system;

[0107] F i (r pi ,θ i ) is the equation of the helical surface determined by the surface coordinates.

[0108] In a helical surface, the lead L i , helix angle λ i and thread pitch diameter r i The relationship is:

[0109] Li =2πr i tanλ i =n i P i

[0110] Where: n i Indicates the number of heads, P i Indicates the thread pitch.

[0111] exist Fig.10 It can be seen that the screw is in the screw coordinate system x s o s z s The tooth profile in the surface, set o se is the center of the concave arc of the screw, and the surface equation of the screw spiral surface is:

[0112]

[0113] In the formula, r ps ,θ s is the parametric coordinate of the screw helical surface, ρ s =1 indicates the upper spiral surface, ρ s =-1 indicates the lower spiral surface; z so and x so is the parameter of the screw helical surface in the coordinate system; L S is the lead of the screw, R s Indicates the screw arc radius.

[0114] Likewise, in Fig.10 It can be seen from the figure that the roller is in the roller coordinate system x r o r z r The tooth profile in the surface, set o re is the center of the roller arc, then the surface equation of the roller spiral surface is:

[0115]

[0116] In the formula, r pr ,θ r is the parametric coordinate of the roller helical surface, ρ r =1 indicates the upper spiral surface, ρ r =-1 indicates the lower spiral surface, z ro and x ro is the parameter of the roller helical surface in the coordinate system, Lr is the lead of the roller, R r is the roller arc radius.

[0117] Likewise, in Fig.10 It can be seen from the figure that the nut is in the nut coordinate system x n o n zn The tooth profile in the surface, the surface equation of the nut helical surface is:

[0118]

[0119] In the formula, r pn ,θ n is the parametric coordinate of the helical surface of the nut, ρ n =1 indicates the upper spiral surface, ρ n =-1 indicates the lower spiral surface, z no and x no is the parameter of the nut helical surface in the coordinate system, L n is the lead of the nut, R n is the nut arc radius.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be covered by the scope of the claims of the present invention. For example, the conical worm in the present invention can be replaced by a worm such as a cylindrical worm, and the practical effect is equivalent.

Claims

1. A linear servo joint for a robot, characterized in that: It includes an end face worm gear mechanism and a reverse planetary roller screw mechanism; The end face worm gear mechanism comprises an end face worm gear and a worm gear which are drivingly connected, and the end face worm gear is driven to rotate by the worm gear; The reverse planetary roller screw mechanism comprises a screw, a nut, a plurality of rollers and a cage, wherein the plurality of rollers are limited on the screw in the height direction by the cage, the screw is drivingly connected to the nut through the plurality of rollers, and the screw is driven by the nut through the plurality of rollers to run in a predetermined direction; The end face worm wheel is fixed to one of the axial end faces of the nut, and the nut is driven to rotate by the worm through the worm wheel.

2. The linear servo joint for a robot according to claim 1, characterized in that: Also included is a housing for assembling an end worm gear mechanism and a reverse planetary roller screw mechanism; The nut is arranged in the middle of the housing through a bearing, the end face worm wheel is fixed on the top end of the nut, and the lead screw has a power output end extending downwardly out of the housing.

3. The linear servo joint for a robot according to claim 2, characterized in that: It also includes a driver and a frameless motor. The driver is in communication connection with the frameless motor. The rotor of the frameless motor is coaxially fixed with the worm. The driving worm of the frameless motor controlled by the driver is in transmission connection with the end worm gear.

4. The linear servo joint for a robot according to claim 3, characterized in that: Also included is an encoder coaxially fixed to the worm, the encoder being communicatively connected to the driver; The installation position of the encoder is opposite to the installation position of the frameless motor in the axial direction of the worm.

5. The linear servo joint for a robot according to claim 2, characterized in that: It also includes a spoke type tension and pressure sensor arranged at the power output end, the force-bearing end of the spoke type tension and pressure sensor is coaxially fixed with the power output end, and the base of the spoke type tension and pressure sensor is limited between the nut and the shell in the height direction.

6. The linear servo joint for a robot according to claim 2, characterized in that: The front end and the rear end of the worm are respectively and correspondingly assembled on the housing through bearings.

7. The linear servo joint for a robot according to claim 2, characterized in that: The bearing for setting the nut in the middle of the shell includes a needle roller bearing, and the needle roller bearing includes two needle roller bearings respectively corresponding to the axial top end and the axial bottom end of the nut.

8. The linear servo joint for a robot according to claim 7, characterized in that: The radial outer wall of the nut extends outward to form a shoulder for assembling the two needle roller bearings. The shoulder is located in the axial middle of the nut to separate and limit the two needle roller bearings in the axial direction of the nut.

9. The linear servo joint for a robot according to claim 2, characterized in that: The shell has an end surface of a power output end with a stop hole, and the power output end is driven to run in a set direction through the stop hole, and the projection of the power output end on the axial direction of the screw is adapted to the stop hole.

10. The linear servo joint for a robot according to claim 1, characterized in that: The central axis of the end worm wheel and the central axis of the worm form an angle of 90°; the lead angle of the worm of the end worm wheel and worm mechanism is smaller than the equivalent friction angle between the meshing gear teeth.

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