In order to make the purpose, technical scheme and advantages of the invention more clear, the invention is further described in detail in combination with the embodiments below. It should be understood that the specific embodiments described herein are only used to explain the invention and are not used to limit the invention.
 see also Figures 1 to 6 , a primary planetary reduction unit, the primary planetary reduction unit 21 includes a primary planet carrier assembly 211 and a primary planet gear 218 installed in the primary planet carrier assembly; The primary planet carrier assembly comprises a primary rotary support disc 212, a primary planet wheel disc 213, a primary planet shaft 214 arranged on the primary planet wheel disc, and the primary planet shaft 214 and the primary planet wheel disc form an integrated forming structure; The primary rotary support plate is fixedly connected with the primary planetary disc 213 through the connecting column 215. In actual production, the primary planetary shaft 214, the connecting column 215 and the primary planetary disc 213 are integrally formed, preferably injection molding. Compared with the prior art, it ensures the support strength of the primary planetary shaft and the connecting column, reduces the process and time of secondary assembly, and ensures the concentricity of the primary rotary support plate and the primary planetary disc, The installation error of the primary planetary reduction unit is avoided, and the instability of the drive operation caused by the accumulation of the installation error of the primary planetary reduction unit to the secondary and tertiary reduction units is solved; A primary planetary gear installation space 216 is formed between the primary rotary support disk and the primary planetary gear disk, and a primary planetary gear 217 is installed on the primary planetary shaft 214 in the primary planetary gear installation space; The primary planetary gear 217 simultaneously engages the primary sun gear 11 and the internal teeth of the ring gear housing 6, and the secondary sun gear 218 is arranged on the primary planetary gear disk; Its working principle is to drive the motor to drive the electric primary sun gear to rotate, the primary sun gear drives three planetary gears to rotate, and the three planetary gears rotate and mesh with the internal teeth of the ring gear housing 6, so as to drive the primary planetary gear disk to coordinate the rotation of the secondary sun gear, realize the primary deceleration and transmit the power to the lower deceleration unit. The primary planetary deceleration unit can be debugged and replaced independently to improve the assembly efficiency, At the same time, ensure the qualified rate of products after assembly.
 An overload protection device 7 is installed on the primary planetary reduction unit. The overload protection device comprises an overload protection disc 7-0, a circular groove 2130 is arranged on the primary planetary disc 213 on the side facing the secondary planetary deceleration unit, an overload protection disc 7-0 is installed in the groove, a central shaft 7-1 is arranged on the overload protection disc, and a secondary sun wheel 219 is arranged on the central shaft. The overload protection is realized through the overload protection disc. The following technical scheme is preferred, The outer circumference of the overload protection disc has convex edges 7-2 along the circumferential direction, and the inner wall of the circular groove of the secondary planetary disc is uniformly provided with limit grooves 2131 matched with the convex edges. Under the normal start-up state, the convex edges are in the limit grooves to drive torque. When the output end is overloaded, the convex edges will move along the limit grooves one by one, thus achieving the purpose of overload protection and driving the motor.
 The outside of the overload protection panel is embedded with an overload protection gland 8; A positioning groove 8-1 is arranged around the overload protection gland, and a positioning block 2132 is arranged on the overload protection disc corresponding to the groove, which meets the lightweight design requirements in actual production. The primary planet carrier components are all plastic components, and the positioning block can fix the overload protection gland by hot melting, but it is not limited to this. The overload protection gland can also be bonded to the overload protection disc by adhesive.
 see also Figures 6 to 10 , a three-stage planetary reduction drive, comprising a drive motor 1, a planetary reduction mechanism installed in the ring gear housing 6, a power output shaft 3 and a motor output flange 4. The power shaft of the drive motor is equipped with a primary sun gear 11; The primary sun gear is connected with the planetary reduction mechanism 2; The planetary reduction mechanism comprises a primary planetary reduction unit 21, a secondary planetary reduction unit 22 and a tertiary planetary reduction unit 23, and an angle detection device 5 for detecting the rotation angle of the power take-off shaft. In order to protect the motor, a motor sealing cover 10 is installed on the driving motor; The first stage planetary reduction unit 21 adopts the first stage planetary reduction unit with the above structure. The two-stage planetary speed reduction unit 22 and the three-stage planetary speed reduction unit 23 can adopt the two-stage planetary speed reduction unit and the three-stage planetary speed reduction unit previously developed by the applicant. See cn108980288a for details. The following technical scheme can also be adopted to further improve the operation stability and assembly efficiency of the three-stage planetary reducer.
 see also Figures 11 to 15 The secondary planetary reduction unit 22 comprises a secondary planet carrier assembly 221 and a secondary planet gear 222 installed in the secondary planet carrier assembly; The secondary planet carrier assembly 221 includes a secondary rotary support disc 223 and a secondary planet wheel disc 224. The secondary planet shaft 225 integrally arranged on the secondary rotary support disc adopts an integrated design structure to ensure the accuracy of the installation position of the secondary planet wheel; The other end of the secondary planetary shaft is fixedly connected with the secondary planetary disc, the secondary planetary disc is integrally provided with a secondary planetary gear holding cylinder 226, the secondary planetary gear holding cylinder is provided with a secondary planetary gear installation groove 227, the secondary planetary shaft 225 is located in the secondary planetary gear holding cylinder, and the secondary planetary gear 222 is installed on the secondary planetary shaft at the position of the secondary planetary gear installation groove; The secondary planetary gear simultaneously engages the secondary sun gear 219 and the internal teeth of the ring gear housing; A three-stage sun gear 228 is arranged in the center of the two-stage planetary gear plate far away from the drive motor side; The secondary planetary gear of the secondary planetary reduction unit engages the secondary sun gear and engages the internal teeth of the ring gear housing to realize the secondary reduction of power, drive the tertiary sun gear to rotate and transmit the power to the lower reduction unit.
 see also Figures 16 to 22The three-stage planetary reduction unit 23 comprises a three-stage planetary carrier assembly 231 and a three-stage planetary gear 232 installed in the three-stage planetary carrier assembly; Wherein the three-stage planetary carrier assembly comprises a three-stage rotary support disc 233 and an angle detection gear disc 234, a three-stage planetary shaft 235 is installed between the three-stage rotary support disc and the angle detection gear disc, and a three-stage planetary gear 235 meshed with the three-stage sun gear 228 is installed on the three-stage planetary shaft; On the side away from the drive motor, the three-stage rotary support plate 23 is integrally provided with a three-stage planetary gear housing sleeve 236. The integrated structure is adopted. On the one hand, the number of parts is reduced. The main purpose is that the position of the three-stage rotary support plate 23 and the three-stage planetary gear housing sleeve 236 is relatively fixed, so as to ensure the position accuracy of the three-stage planetary gear installed therein and have the effect of sound absorption; The side wall of the three-stage planetary gear housing sleeve is provided with a notch 237, and the three-stage planetary gear extends out of the notch to mesh with the inner teeth of the ring gear housing; An angle detection gear plate connecting column 238 is installed on the end face of the support wall of the three-stage planetary gear housing sleeve adjacent to the notch; Angle detection gear plate connecting column connection angle detection gear plate 234; The angle detection gear plate is connected with the power take-off shaft 3. The angle detection gear plate and the power take-off shaft 3 can be an integrated structure or a split assembly structure. The angle detection gear plate and the power take-off shaft are fixed and installed between the overall assembly; The three-stage planetary gear of the three-stage planetary reduction unit meshes with the three-stage sun gear, realizes the three-stage reduction of power with the inner gear of the ring gear housing, drives the three-stage sun gear to rotate, transmits the power to the power output shaft 3 through the angle detection gear disc, outputs the power, and drives the angle detection gear disc to rotate within the set angle range.
 The angle detection device 5 includes an angle detection box 9 arranged on the side of the shell close to the end of the power output shaft, a flange box cover 9-1 is installed on the angle detection box on the side away from the drive motor, the power output shaft extends out of the flange box cover, and an angle detection element 9-2 for detecting the rotation angle of the power output shaft is installed in the angle detection box.
 The angle detection element adopts a gear potentiometer, the gear potentiometer is installed on the potentiometer installation shaft 9-3 in the angle detection box, and the potentiometer gear 9-4 of the gear potentiometer meshes with the angle detection gear plate 234; An angle sensor drive shaft 9-5 is coaxially arranged on the potential gear, and the angle sensor drive shaft is connected with the angle sensor 9-6. The rotation angle of the power take-off shaft is detected and fed back in real time through the gear potentiometer to reflect the opening of the actuator (box cover) installed with the driver of the invention.
 To sum up, the invention realizes the independence of the primary reduction unit, and then the driver is assembled as a whole to improve the assembly efficiency. At the same time, the primary planetary reduction unit can be replaced and debugged independently; The primary reduction unit of a planetary reduction drive adopts an independent assembly structure, and the position between various parts remains relatively stable, which avoids the abnormal sound caused by the accumulation of assembly errors of the primary planetary reduction unit in the prior art, and provides a foundation for the stable transmission of power to the next stage.
 The above is only a preferred embodiment of the invention and is not intended to limit the invention. Any modification, equivalent replacement and improvement made within the spirit and principles of the invention, such as materials and dimensions, shall be included in the protection scope of the invention.