Large-reduction-ratio robot joint actuator with built-in speed reduction structure

Abstract

The invention discloses a large reduction ratio robot joint actuator with a built-in speed reduction structure, which comprises two inner gear rings, a plurality of planet gears, an actuator shell and an actuator cover plate, a containing space is jointly formed between the actuator shell and the actuator cover plate, and a motor stator and a motor rotor are mounted in the containing space. The motor stator is fixed to the actuator shell. A plurality of planet gears are arranged in the two inner gear rings, the planet gears are evenly distributed in the circumferential direction of the inner gear rings, each planet gear is meshed with the two inner gear rings, and the meshing center distances are kept equal; the two inner gear rings are the same in modulus and unequal in tooth number, and the two inner gear rings are the fixed gear ring and the output gear ring respectively. The whole axial size of the actuator is compact, under the condition that a speed reduction structure is extremely simple, the larger speed reduction ratio, the larger gear modulus and the larger gear width are obtained compared with a conventional speed reduction scheme, the strength and the bearing capacity of the actuator are greatly improved, the service life of the actuator is greatly prolonged, the assembly technology is simple, cost is low, and the structure is reliable.

Description

Technical Field

[0001] The invention belongs to the technical field of robots, and in particular relates to a joint part in a robot body structure. Background Art

[0002] In the field of robot applications, the number of degrees of freedom, movement ability and precise control of various complex postures of its products are all determined and completed by actuators in different parts of the robot body structure. The actuator is a basic motion and control unit composed of a motor, a reducer, a motor drive controller, and other optional accessories. When working, the robot not only has to bear a specific workload (such as heavy objects grasped by the manipulator, the workload carried by the legged robot, etc.), but also needs to overcome the weight of its own structure. When the posture and movement are complex, the actuator needs to burst out a very high torque. For bipedal humanoid robots, quadrupedal robots and multi-legged robots that carry lithium batteries themselves, due to the heavy weight of lithium batteries, the highly complex structure of the robot body and the integration of various sensors, electronic modules and computing control units, the robot has high requirements on appearance and volume. Therefore, the system integration, complexity, technical difficulty, etc. are much higher than those of conventional industrial robots. Therefore, bipedal humanoid robots are often praised as the crown of modern manufacturing. The joint actuator is the most critical core component in the robot body structure, and its performance directly determines the robot's basic movement ability, flexibility and posture control ability.

[0003] The existing technology is to make the motor work in the high speed and high efficiency area by matching the brushless motor with the reducer, and rely on the reduction of the reducer to provide the amplified output torque. The existing actuator products adopt one or more of the following technologies:

[0004] A. The motor and reducer are designed and manufactured separately, and the last two components are assembled in axial series. This solution will cause the entire actuator to have too large axial dimensions, increase weight, and too many parts, which will increase process costs and reduce reliability. The strength and load-bearing capacity of the gear are determined by the gear module and gear width. The gear module is generally difficult to adjust due to the limitation of radial dimension space. In order to avoid excessive axial dimensions, the gear width must be reduced, resulting in insufficient gear load-bearing capacity, which shortens the life of the reducer gear.

[0005] Figure 3-Figure 4This is a common design scheme in robot joint actuators. From this design scheme diagram, we can see that the sun gear of the planetary reducer is press-fitted onto the motor rotor with an interference fit, and the motor and reducer are in an axial series structure. In order to prevent the axial length of the entire actuator from being too long, the tooth width of all gears of the reducer (sun gear, planetary gear, inner ring gear) is designed to be very small (generally 3-5mm), so the gear strength is low, and the load-bearing capacity and life are very limited.

[0006] B. In order to increase the output torque of the actuator, the most common method is to increase the reduction ratio of the reducer to improve the amplification capacity of the motor torque. There are two common methods. One is to increase the number of teeth of the internal gear (which will also reduce the gear modulus and reduce the gear strength) and appropriately reduce the number of sun teeth (too few teeth will cause gear root cutting and reduce the gear strength) to increase the reduction ratio. Another method is to increase the reduction ratio by axially connecting two or more stages of planetary reducers in series. Multi-stage series connection will also face the problem of reduced actual gear width at each stage of transmission, too many gears, and the gears and planetary carriers cannot be effectively supported by bearings. Overall, it will bring many adverse effects such as complex process, difficult assembly, reduced rotation accuracy and stiffness, high cost, and low reliability.

[0007] Figure 1 and Figure 2The common two-stage planetary axial series scheme in robot joint actuators is shown. In this scheme, the output torque of the motor is input into the first-stage planetary reducer through the first-stage sun gear pressed on the motor rotor. The first-stage planetary reducer consists of the first-stage sun gear, the first-stage planetary gear, the first-stage inner gear ring (rigidly fixed on the actuator housing), and the first-stage planet carrier. Please note that the first-stage planetary gear is supported on a thin sheet-type (first-stage) planetary carrier through its planetary gear pin on one side. The first-stage planetary carrier is in a "floating state" and cannot adopt reliable and effective support methods such as bearings. The first-stage planetary carrier has a poor support effect on the first-stage planetary gear. One end of its planetary gear pin is supported on the planetary carrier, and the other end is suspended in the air, in a "cantilever beam" state, with poor rigidity. The output torque of the first-stage reducer is output by the first-stage planet carrier, and the first-stage output torque is input into the second-stage planetary reducer through the second-stage sun gear rigidly connected to it. The second-stage planetary reducer is composed of the second-stage sun gear, the second-stage planetary gear, the second-stage inner gear ring (rigidly fixed on the actuator housing), and the second-stage planet carrier (output flange). Its principle and structure are the same as the first stage, and its disadvantages are also similar, that is, the second-stage planet carrier (output flange) also supports the second-stage planetary gear in a "cantilever beam" manner, and the second-stage planetary gear cannot be reliably and effectively supported. This two-stage planetary reduction structure cannot be effectively and reliably supported, whether in the axial or radial direction. The entire structure has many parts, and the structure and assembly are very complex. The overall structural reliability and accuracy are low (according to the accuracy and reliability theory, the more parts there are, the greater the risk of failure, which increases the complexity of the system, and the overall reliability and accuracy will also decrease sharply). Because there are many parts, the overall noise of the actuator will also increase due to the accumulation of various errors. Because the torque of the first stage reducer is small and the torque of the second stage reducer is large, the first stage has a smaller module and smaller tooth width, and the second stage (output stage) has a larger module and larger tooth width. This will cause the need to prepare gear hobs with different modules, increase the specifications, types and costs of gear processing tools, and lead to disadvantages such as poor economic performance and increased management costs. It can be clearly seen from the structure diagram that the tooth width of each stage of the gear is still very small, generally around 4mm, and the gear bearing capacity is extremely limited.

[0008] Figure 5Another common "double planetary" reduction scheme in robot joint actuators is demonstrated, that is, the single "planetary gear" in the conventional planetary reducer is replaced by a gear set consisting of two gears, one large and one small, which are axially rigidly connected. This large and small gear set is often called a "double planetary gear". In the double planetary gear, there is a natural reduction ratio between the two gears of different sizes. The output power of the motor is first transmitted to the large gear in the double planetary gear through its meshing motion by the sun gear, and then through the inherent reduction of the double planetary gear, it is output by the small gear in the double planetary gear and meshes with the inner ring gear. The double planetary gear as a whole and the planet carrier participate in the transmission of the entire reducer. Therefore, the reduction ratio of the double planetary gear is slightly larger than that of the conventional single-stage planetary reducer. The common reduction ratio range is 10-18 (it will be difficult to increase it further). It can be clearly seen from the scheme diagram that the total axial width of the reducer of the double planetary scheme will be larger (the axial width of the double planetary large gear is increased), and the overall outer diameter of the double planetary large gear will be larger than the outer diameter of the inner gear ring, so the overall radial size of the reducer will also increase. At the same time, there are strict requirements for the relative radial position between the teeth of the large and small gears in the double planetary gears, and a "tooth alignment" operation is required, which is troublesome in terms of process and will increase costs.

[0009] C. Another common deceleration solution is to use a harmonic reducer (see Figure 6 ). The principle of the harmonic reducer is that the output power of the motor is connected to the wave generator, the rigid wheel is fixed on the housing, and the flexible wheel outputs power (the flexible wheel is fixed to the output flange with screws); the ultra-thin flexible bearing on the wave generator and the wall thickness of the flexible wheel must be made very thin, so that the required specific elastic deformation can be synchronously generated with the rotation of the wave generator, pushing the teeth on the flexible wheel and the teeth on the rigid wheel to continuously perform slow staggered tooth rotation motion; the advantage of the harmonic reducer is that the reduction ratio is slightly larger (commonly between 40-150), but it is also limited to compared with the conventional reduction scheme ( Except for this patent technology), harmonic drive also has its technical weaknesses: the wall thickness of its flexible wheel and flexible bearing is very thin, the material rigidity is poor, there is elastic angle deformation and hysteresis at the output and input ends, because the material is in uninterrupted elastic deformation, its fatigue strength is far lower than the strength of common gear materials, the flexible wheel and flexible bearing are easily damaged, the load-bearing capacity and life are limited, the raw materials need to be imported, the price is expensive (the price is several to dozens of times that of the planetary reducer), the transmission efficiency is not advantageous (generally about 75%, the efficiency is still low), etc.

[0010] In summary, the existing robot joint actuators have the following shortcomings: the reduction ratio is difficult to improve, the gear strength and load-bearing capacity are generally low (small module, small gear tooth width), the conventional reducer structure is too complicated, assembly is difficult, the reliability is low, the overall size is too large, there are too many parts, the weight is too heavy, and the cost is high. Summary of the invention

[0011] The main technical problem solved by the present invention is to provide a large reduction ratio robot joint actuator with a built-in reduction structure. The overall axial size is extremely compact. With an extremely streamlined reduction structure, a larger reduction ratio, a larger gear module and width are obtained than conventional reduction schemes. The strength, bearing capacity and life are greatly improved, the assembly process is simple, the cost is low, and the structure is reliable.

[0012] In order to solve the above technical problems, a technical solution adopted by the present invention is: a large reduction ratio robot joint actuator with a built-in reduction structure, comprising two inner gear rings, a plurality of planetary gears, an actuator housing and an actuator cover plate, wherein the actuator housing and the actuator cover plate together form an accommodating space, wherein a motor stator and a motor rotor are installed inside the accommodating space, and the motor stator is fixed to the actuator housing;

[0013] A plurality of planetary gears are arranged inside the two inner gear rings, and the planetary gears are evenly arranged along the circumference of the inner gear rings, and each of the planetary gears is meshed with the two inner gear rings, and the meshing center distances are kept equal;

[0014] The two inner gear rings are inner gear rings with the same module and different numbers of teeth. The two inner gear rings are respectively a fixed gear ring and an output gear ring. The fixed gear ring is installed on the actuator housing, and the output gear ring is installed on the output flange. The planetary gears revolve around the central axes of the two inner gear rings under the direct or indirect drive of the motor rotor, and the planetary gears can rotate along their own central axes. The two inner gear rings and several planetary gears constitute a single-stage reduction structure. The overall axial size is extremely compact. With an extremely streamlined reduction structure, a larger reduction ratio, a larger gear module and a larger width are obtained than conventional reduction schemes, and its strength, bearing capacity and life are greatly improved.

[0015] Furthermore, the difference in the number of teeth between the fixed gear ring and the output gear ring is equal to the number of the planetary gears.

[0016] Furthermore, a plurality of the planetary gears are rotatably connected to a planetary carrier, and the planetary carrier is fixed to the motor rotor.

[0017] Furthermore, the gear teeth on the surface of the planetary gear are herringbone teeth, and the herringbone teeth are composed of two mutually symmetrical helical teeth.

[0018] Furthermore, a hollow shaft is installed at the center of the actuator, and the hollow shaft is fixed to the output flange, which can realize "hollow wiring" in robot wiring, reduce the difficulty of wiring, avoid cable exposure, and avoid wire damage while being aesthetically pleasing.

[0019] Furthermore, a sun gear is installed at the center of the actuator, the sun gear is fixed to the motor rotor, a plurality of the planetary gears are located between the sun gear and the two inner gear rings, and a plurality of the planetary gears are respectively meshed with the sun gear.

[0020] Furthermore, a central through hole is provided at the center of the sun gear, which can realize "hollow wiring" in robot wiring, reduce the difficulty of wiring, avoid cable exposure, and avoid wire damage while being aesthetically pleasing.

[0021] Furthermore, the inner circumference of the output flange or the actuator housing is provided with a circle of grease storage grooves or grease storage holes arranged in a ring shape.

[0022] Furthermore, the output flange is provided with pin columns and threaded holes for providing external connection and transmitting power.

[0023] The beneficial effects of the present invention include at least the following points:

[0024] The two inner gear rings and the plurality of planetary gears of the present invention constitute a single-stage reduction structure. The two inner gear rings are provided with a plurality of planetary gears, which are evenly arranged along the circumference of the inner gear rings. Each planetary gear meshes with the two inner gear rings and the meshing center distances are kept equal. The overall axial dimension is extremely compact. Under the condition of an extremely streamlined reduction structure, a larger reduction ratio, a larger gear module and a larger width are obtained than conventional reduction schemes. The strength, bearing capacity and life of the gears are greatly improved. The assembly process is simple, the cost is low and the structure is reliable.

[0025] The actuator created by the present invention has a hollow shaft or a central through hole in the center, which can realize "hollow wiring" in robot wiring, reduce the wiring difficulty, avoid cable exposure, and avoid wire damage while being beautiful;

[0026] The invention realizes a large gear module, a large tooth width and a large transmission ratio, which is 2.5 times larger than the gear module in the conventional robot joint actuator, 3 times larger than the tooth width, and the load-bearing capacity and life are improved by more than 7-10 times. The reduction ratio can be realized in a wide range of 14-400, which has significant advantages over multi-stage planetary series solutions and harmonic reducers.

[0027] The present invention presses the sun gear onto the motor rotor, and the movement and power of the motor are input into the sun gear by the motor rotor, thereby omitting the planet carrier, which can greatly reduce the cost of the reduction structure and has significant cost-effectiveness. In a planetary reducer, the cost of the planet carrier accounts for at least 1 / 3 of the total cost. The overall structure of the planet carrier is complex, and the several planetary gear pin holes of the planet carrier require extremely high-precision processing equipment to be processed to ensure the high precision of the planetary rotation. Therefore, this part is omitted, and the more complicated and cumbersome, time-consuming and labor-intensive planetary gear press-fitting (labor costs account for a large proportion) during assembly is eliminated, which can greatly reduce the assembly and process costs, so that the total cost of the reduction structure can be reduced by more than 70%. It is worth mentioning that due to the floating of several planetary gears evenly distributed around the circumference, when the planetary gears are subjected to the common torque and force of the inner ring gear and the sun gear, the relative positions of the planetary gears can be adaptively adjusted to ensure that the planetary gears distributed around the circumference can evenly share the torque and force, realize the automatic and average distribution of the load between the planetary gears, and extend the life of the reduction structure.

[0028] The reduction ratio of the present invention is larger than that of the harmonic reducer. Secondly, due to its natural disadvantages in principle and material, the strength and durability (the fatigue life of the material will be much lower than the meshing life of the gear material) of the harmonic reducer are much lower than the large-module, large-reduction ratio planetary gear transmission of this patent. From the transmission efficiency point of view, the efficiency of the harmonic reducer is about 75%, while the transmission efficiency of the technology of this patent is about 90%. Finally, the cost of the harmonic reducer is several to dozens of times that of the planetary reducer, which poses a great obstacle to the cost reduction and commercial mass production of humanoid robots. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a cross-sectional view of a two-stage planetary transmission actuator of the prior art;

[0030] Figure 2 It is an exploded schematic diagram of a two-stage planetary transmission actuator of the prior art;

[0031] Figure 3 is a cross-sectional view of a series structure actuator of the prior art;

[0032] Figure 4 It is an exploded schematic diagram of a series structure actuator of the prior art;

[0033] Figure 5 It is an exploded schematic diagram of a double planetary gear reducer actuator in the prior art;

[0034] Figure 6 is a cross-sectional view of a harmonic reducer in the prior art;

[0035] Figure 7 is a cross-sectional view of embodiment 1 of the present invention;

[0036] Figure 8 is an exploded schematic diagram of the first embodiment of the present invention;

[0037] Fig. 9 is a schematic structural diagram of a planet carrier and a planet gear according to a first embodiment of the present invention;

[0038] Fig.10 is a cross-sectional view of a second embodiment of the present invention;

[0039] Fig.11 is an exploded schematic diagram of the second embodiment of the present invention;

[0040] Fig.12 It is a structural schematic diagram of the output flange of the present invention;

[0041] The parts in the accompanying drawings are marked as follows:

[0042] 1. Planetary gear; 11. Herringbone gear; 21. Actuator housing; 22. Actuator cover; 31. Motor stator; 32. Motor rotor; 4. Fixed gear ring; 5. Output gear ring; 6. Output flange; 61. Output flange support bearing; 7. Planet carrier; 71. Planet carrier support bearing; 8. Hollow shaft; 81. Hollow shaft support bearing; 9. Sun gear; 91. Center through hole; 92. Sun gear support bearing; 10. Grease storage hole. DETAILED DESCRIPTION

[0043] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0044] Embodiment 1: A large reduction ratio robot joint actuator with a built-in reduction structure, such as Figure 7-Figure 8 As shown, it includes two inner gear rings, a plurality of planetary gears 1, an actuator housing 21 and an actuator cover plate 22. The actuator housing 21 and the actuator cover plate 22 together form an accommodation space. A motor stator 31 and a motor rotor 32 are installed inside the accommodation space. The motor stator 31 is fixed to the actuator housing 21.

[0045] In this embodiment, an outer rotor brushless motor is installed inside the accommodating space, and the outer rotor brushless motor includes a motor stator and a motor rotor;

[0046] A plurality of the planetary gears 1 are arranged inside the two inner gear rings, and the planetary gears 1 are evenly arranged along the circumference of the inner gear rings. Each of the planetary gears 1 meshes with the two inner gear rings, and the meshing center distances are kept equal;

[0047] The two inner gear rings are inner gear rings with the same modulus and different numbers of teeth, and the two inner gear rings are respectively a fixed gear ring 4 and an output gear ring 5, the fixed gear ring 4 is mounted on the actuator housing 21, and the output gear ring is mounted on the output flange 6, the planetary gear 1 revolves around the central axis of the two inner gear rings under the direct or indirect drive of the motor rotor 32, and the planetary gear 1 can rotate along its own central axis, realizing a large gear modulus, a large tooth width and a large transmission ratio, which is 2.5 times larger than the gear modulus in the conventional robot joint actuator, and 3 times larger than the tooth width, and the load-bearing capacity and life are increased by more than 7-10 times, and the reduction ratio can achieve a wide range of 14-400, which has significant advantages compared with the multi-stage planetary series scheme and the harmonic reducer;

[0048] During specific implementation, a motor drive controller (not shown in the figure) is installed on the actuator cover.

[0049] The difference in the number of teeth between the fixed gear ring 4 and the output gear ring 5 is equal to the number of the planetary gears 1. The number of the planetary gears 1 is generally 2-4. When the planetary gear revolves one circle, due to the specific difference in the number of teeth between the two inner gear rings, the output gear ring will only advance or retreat relative to the fixed gear ring by a number of tooth pitches equal to the difference in the number of teeth. Therefore, the output gear ring forms a reduction ratio relative to the revolution of the planetary gear, and the reduction ratio = the number of teeth of the output gear ring / (the number of teeth of the output gear ring-the number of teeth of the fixed gear ring). When the number of teeth of the output gear ring>the number of teeth of the fixed gear ring, the rotation direction of the output gear ring is consistent with the revolution direction of the planetary gear, and vice versa.

[0050] A plurality of the planetary gears 1 are rotatably connected to a planetary carrier 7 , and the planetary carrier 7 is fixed to the motor rotor 32 .

[0051] like Fig. 9 As shown, the gear teeth on the surface of the planetary gear 1 are herringbone teeth 11, and the herringbone teeth 11 are composed of two mutually symmetrical helical teeth. Of course, in this embodiment, the gears of the planetary gear can also be helical teeth or straight teeth, but are not limited to this, as long as other tooth structures that can make the planetary gear and the inner ring gear engage are acceptable.

[0052] A hollow shaft 8 is installed at the center of the actuator, and the hollow shaft 8 is fixed to the output flange 6. In the present embodiment, the hollow shaft is provided so that the robot cable can pass through the hollow hole which is large enough. If threading is not considered, a solid shaft can also be directly provided.

[0053] A planet carrier support bearing 71 is provided between the planet carrier and the actuator housing, an output flange support bearing 61 is provided between the output flange and the actuator housing, and a hollow shaft support bearing 81 is provided between the hollow shaft and the planet carrier.

[0054] In this embodiment, the Figure 7-Figure 9 In the embodiment, the rotor of the motor is directly locked on the planet carrier, and the rotation of the motor rotor and the revolution of the planetary gear are kept equal and synchronous, that is, the sun gear in the conventional actuator is eliminated, which can bring the following significant benefits:

[0055] 1. The sun gear is eliminated and the number of parts is simplified, which can significantly reduce the cost of parts and greatly improve reliability. It has significant advantages over common two-stage planetary series and double-connected planetary transmission solutions;

[0056] 2. The sun gear in the conventional planetary reduction scheme needs to be pressed onto the motor rotor with high precision to ensure coaxiality. Since the sun gear is eliminated, all process difficulties and costs are reduced;

[0057] 3. Since the sun gear is removed, the space originally occupied by the sun gear is saved, forming a large middle hole space, and the robot cables can pass through this large enough hollow hole to achieve hollow wiring. In contrast, the design of existing conventional robot actuators is extremely difficult to open the middle hole, and it is difficult to achieve hollow wiring. Therefore, in the current common humanoid robots, the actuator cables are generally exposed to the outside, which affects the appearance. When the robot moves, it is easy to hook the exposed cables, which poses a considerable risk;

[0058] 4. The gear module in this solution is 1.25, and the width of the inner gear ring reaches 14mm. Compared with the robot joint actuators of the same size and reduction ratio on the market, their module is generally only about 0.5, and the tooth width is mostly 4-5mm. Since the strength and load-bearing capacity of the gear are jointly determined by the gear module and tooth width, the load-bearing capacity and service life of the reduction structure of this solution can be greatly improved by at least 7-10 times;

[0059] 5. In this embodiment, since the planetary frame only receives the output torque of the motor (relatively small) and does not bear the output torque after deceleration (relatively large), the planetary frame can be made of light alloy (such as aluminum alloy, etc.), and its weight can be reduced to 1 / 3 of the original steel planetary frame in the general reducer, which is extremely beneficial to the lightweight of the robot;

[0060] 6. Helical gear transmission has significant advantages over spur gear transmission in that it has large meshing overlap, low noise, smooth transmission, and smaller gear backlash, but its disadvantage is the presence of axial force. In this embodiment, the planetary gear can adopt a herringbone gear scheme, and the corresponding two inner ring gears respectively adopt helical gears with opposite rotation directions; since the herringbone gears have helical gears with opposite rotation directions on both sides, the axial forces on both sides can be offset. When the robot joint actuator frequently rotates forward and reverse, it retains the many advantages of helical gear meshing while overcoming the disadvantage of the axial force of conventional helical gears, which has significant technical advantages.

[0061] 7. In this embodiment, an integral planetary frame is adopted, that is, the planetary frame is a complete whole, and the pin holes of the planetary wheels in the planetary frame are processed at one time by a high-precision machine tool. The precision, consistency, rigidity, etc. of the pin holes on both sides of the planetary wheels can reach high precision and guarantee, and higher transmission precision can be obtained. The backlash of the reduction structure can be 1-3 arc minutes. Conventional robot joint actuators, the planetary frame of the reducer is mostly split (that is, the planetary frame is divided into a planetary frame A and a planetary frame B, and then axially combined by screws, etc.), which has the disadvantages of low processing accuracy, large error, poor rigidity, etc. The backlash of the reducer is generally about 15 arc minutes, so it can overcome many disadvantages of the split planetary frame, so as to achieve high rigidity, high precision, very small backlash and very low noise, and achieve precision-level transmission quality;

[0062] The working principle of the first embodiment is as follows: the motor rotor drives the planetary carrier to rotate, the planetary carrier drives a plurality of planetary gears to revolve, and because the fixed ring gear meshes with the planetary gears, the planetary gears rotate, the planetary gears drive the output ring gear to rotate, and the output ring gear drives the output flange to rotate.

[0063] Embodiment 2: The structure of this embodiment is basically similar to that of embodiment 1, except that Figure 10-11 As shown, a sun gear 9 is installed at the center of the actuator of this embodiment, and the sun gear 9 is fixed to the motor rotor 32. Several planetary gears 1 are located between the sun gear 9 and the two inner gear rings, and several planetary gears 1 are respectively engaged with the sun gear 9.

[0064] A central through hole 91 is provided at the center of the sun gear 9 .

[0065] An output flange support bearing is provided between the output flange and the actuator housing, and a sun gear support bearing 92 is provided between the sun gear and the output flange.

[0066] When a very high reduction ratio is required, Figure 10-11Embodiment: The sun gear is retained and fixedly pressed onto the motor rotor. The movement and power of the motor will be input into the sun gear by the motor rotor. The sun gear drives the circumferentially distributed planetary gears to perform both self-rotation and orbital motion. The output after deceleration is the orbital motion of the planetary gears (the planetary gears orbit in sync with the planet carrier, and the planet carrier is removed in this embodiment). This is the first-stage reduction principle (the same as the principle of conventional planetary reducers). Due to the existence of the output ring gear, the principle of the second-stage reduction formed by the planetary gear revolution (the first-stage reduction output) and the two inner ring gears has been briefly explained above. Therefore, the total reduction ratio is the first-stage reduction ratio × the second-stage reduction ratio, so a higher reduction ratio can be obtained;

[0067] In this embodiment, the revolution and rotation of the planetary gear are not affected by external torques. Through the force analysis of a single planetary gear, it can be known that the planetary gear is only subjected to three torques: the first is that the planetary gear bears the torque transmitted by the sun gear (its torque load is evenly distributed within the entire gear width of the planetary gear), the second is that half of the planetary gear is subjected to the reaction torque of the fixed gear ring (its torque load is evenly distributed within the half-side tooth width of the planetary gear), and the third is that the other half of the planetary gear is subjected to the reaction torque of the output gear ring (its torque load is evenly distributed within the half-side tooth width of the planetary gear). The combined torque of the three torques on the planetary gear is zero. Therefore, the "planet carrier" used to fix and support the planetary gear and its revolution in the conventional planetary reducer can be eliminated in this embodiment, and the axial space of the planetary carrier is limited by the outer shell seat on the left and the output flange surface on the right.

[0068] This embodiment can achieve the following significant benefits:

[0069] 1. The omission of the planetary carrier can greatly reduce the cost of the reduction structure, which has significant cost-effectiveness. In a planetary reducer, the cost of the planetary carrier accounts for at least 1 / 3 of the total cost. The overall structure of the planetary carrier is complex, and the several planetary gear pin holes of the planetary carrier require extremely high-precision processing equipment to ensure the high precision of the planetary rotation. Therefore, omitting this part and canceling the more complicated and cumbersome, time-consuming and labor-intensive planetary gear press assembly (labor costs account for a large proportion) during assembly can greatly reduce assembly and process costs, so that the total cost of the reduction structure can be reduced by more than 70%.

[0070] 2. In this embodiment, the sun gear still maintains a relatively large hollow through hole, which can realize hollow wiring, thereby reducing the difficulty of robot wiring and avoiding the risks of cable exposure, damage, scratches, etc. In contrast, the design of existing conventional robot actuators is extremely difficult to open a hole in the middle, and the exposure of cables will bring many disadvantages.

[0071] 3. This embodiment can achieve a very large reduction ratio (the economical reduction ratio range is 30 to 400), which is larger than the reduction ratio of the harmonic reducer (40-150), and is also incomparable to the reduction ratio of the conventional multi-pole planetary series reducer.

[0072] 4. The gear module and tooth width in this embodiment remain the same as those in the first embodiment, so the strength, bearing capacity and life of the gear are exactly the same as the advantages in the first embodiment.

[0073] 5. Due to the floating of several planetary gears evenly distributed around the circumference, when the planetary gears are subjected to the common torque and force of the inner ring gear and the sun gear, the relative positions of the planetary gears can be adaptively adjusted to ensure that the planetary gears distributed around the circumference can evenly share the torque and force, realize automatic and even distribution of the load between the planetary gears, extend the life of the reduction structure, and avoid the premature failure and end of life of a few planetary gears that are subjected to excessive loads due to uneven load distribution.

[0074] In contrast, in conventional planetary reducers with planetary carriers, if the positioning of the planetary pin holes is poor, a larger meshing side clearance must be reserved for the gears (to prevent the gears from meshing and getting stuck or stuck). Since the position of the planetary gears is limited by the planetary pins on the planetary carrier and cannot move to achieve automatic compensation, when the planetary gears are subjected to force, the load distribution will be uneven, that is, some planetary gears will bear too much load and their teeth will break, or their life will be rapidly reduced and they will fail prematurely due to excessive load. Other individual planetary gears may even experience meshing suspension due to bearing smaller loads.

[0075] 6. In this embodiment, the center hole of the planetary gear mainly serves as an assembly process hole (for uniform circumferential positioning during assembly). The hole can store grease. There is also a circle of grease storage holes or grooves on the output flanges on both side faces and the actuator housing seat to store grease to ensure that the planetary gear ends and gear meshing parts have sufficient grease reserves and are fully lubricated, thereby extending the life of the reduction structure.

[0076] The working principle of the second embodiment is as follows: the motor rotor drives the sun gear to rotate. Since the sun gear meshes with the planetary gear, the planetary gear revolves under the drive of the sun gear. The planetary gear rotates due to the reaction force of the fixed gear ring. The planetary gear drives the output gear ring to rotate, and the output gear ring drives the output flange to rotate.

[0077] like Fig.12 As shown, the inner circumference of the output flange 6 or the actuator housing 21 is provided with a circle of grease storage grooves or grease storage holes 10 arranged in a ring shape.

[0078] The output flange 6 is provided with pin columns and threaded holes for providing external connection and transmitting power.

[0079] The above are only embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A robot joint actuator with a large reduction ratio and a built-in reduction structure, characterized in that: The invention comprises two inner gear rings, a plurality of planetary gears (1), an actuator housing (21) and an actuator cover plate (22), wherein the actuator housing and the actuator cover plate together form a housing space, a motor stator (31) and a motor rotor (32) are installed inside the housing space, and the motor stator is fixed to the actuator housing; A plurality of planetary gears are arranged inside the two inner gear rings, and the planetary gears are evenly arranged along the circumference of the inner gear rings, and each of the planetary gears is meshed with the two inner gear rings, and the meshing center distances are kept equal; The two inner gear rings are inner gear rings with the same module and different numbers of teeth. The two inner gear rings are respectively a fixed gear ring (4) and an output gear ring (5). The fixed gear ring is installed on the actuator housing, and the output gear ring is installed on the output flange (6). The planetary gear revolves around the central axis of the two inner gear rings under the direct or indirect drive of the motor rotor, and the planetary gear can rotate along its own central axis.

2. The robot joint actuator with a large reduction ratio and a built-in reduction structure according to claim 1 is characterized in that: The difference in the number of teeth between the fixed gear ring and the output gear ring is equal to the number of the planetary gears.

3. The robot joint actuator with a large reduction ratio and a built-in reduction structure according to claim 1 is characterized in that: A plurality of the planetary wheels are rotatably connected to a planetary frame (7), and the planetary frame is fixed to the motor rotor.

4. The robot joint actuator with a large reduction ratio and a built-in reduction structure according to claim 1, characterized in that: The gear teeth on the surface of the planetary gear are herringbone teeth (11), and the herringbone teeth are composed of two mutually symmetrical helical teeth.

5. The robot joint actuator with a large reduction ratio and a built-in reduction structure according to claim 1, characterized in that: A hollow shaft (8) is installed at the center of the actuator, and the hollow shaft is fixed to the output flange.

6. The robot joint actuator with a large reduction ratio and a built-in reduction structure according to claim 1, characterized in that: A sun gear (9) is installed at the center of the actuator, the sun gear is fixed to the motor rotor, a plurality of planetary gears are located between the sun gear and the two inner gear rings, and a plurality of planetary gears are respectively meshed with the sun gear.

7. The robot joint actuator with a large reduction ratio and a built-in reduction structure according to claim 1, characterized in that: A central through hole (91) is provided at the center of the sun gear.

8. The robot joint actuator with a large reduction ratio and a built-in reduction structure according to claim 1, characterized in that: The inner circumference of the output flange or the actuator housing is provided with a circle of grease storage grooves or grease storage holes (10) arranged in a ring.

9. The robot joint actuator with a large reduction ratio and a built-in reduction structure according to claim 1, characterized in that: The output flange is provided with pin columns and threaded holes for providing external connection and transmitting power.

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