Ultra-thin large-hollow lightweight speed reducer

Abstract

The application provides an ultrathin large-hollow lightweight speed reducer, and relates to the technical field of speed reducers.The speed reducer comprises a wave generator, a flexible bearing, a flexible gear, a rigid gear one and a rigid gear two.The axial length of the flexible gear is not more than the total axial length of the rigid gear one and the rigid gear two, and the total axial length of the flexible bearing is not more than the axial length of the flexible gear.At least one of the wave generator, the flexible bearing, the flexible gear, the rigid gear one and the rigid gear two is made of engineering plastic.The ratio of the outer diameter of the speed reducer to the total axial length thereof is greater than 3:1, and the ratio of the hole diameter of the wave generator to the total axial length of the speed reducer is greater than 1:1.The outer wall of the flexible gear is provided with first meshing teeth and second meshing teeth which are different in tooth shape.The first meshing teeth are engaged with the inner teeth of the rigid gear one in the same number of teeth or the same number of difference teeth, and the second meshing teeth are engaged with the inner teeth of the rigid gear two in the same number of teeth or the same number of difference teeth.The number of difference teeth between the first meshing teeth and the inner teeth of the rigid gear one and the number of difference teeth between the second meshing teeth and the inner teeth of the rigid gear two are different.The application can meet the requirements of small size, lightweight, high torque density and low vibration noise of the module.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of speed reducer, in particular to an ultra-thin large hollow lightweight speed reducer. BACKGROUND

[0002] The robot joint module is the core component of the small robot such as collaborative robot, mobile robot and humanoid robot, and the modular joint module of the speed reducer and motor realizes the rapid and convenient assembly and maintenance of the robot. At present, the robot joint module is being applied more and more in the service robot industry, and the small size, large hollow, flat shape, lightweight, high torque density and high reliability of the module are strictly required.

[0003] The existing robot joint module is mostly integrated design of harmonic reducer with single rigid wheel structure and frameless torque motor, the axial length is too long, the hollow hole is small, and the shape size cannot meet the use requirement. In addition, the rigid wheel and the flexible wheel in the traditional harmonic reducer are made of metal material, which is formed by precise mechanical processing and multi-channel heat treatment and surface process, although the high strength and high fatigue resistance of the working tooth part are realized, but the lightweight requirement of the new joint module cannot be realized. The special engineering plastics such as PTFE, PPS, PAI and PEEK have a series of excellent comprehensive performance such as light weight, high temperature resistance, wear resistance, corrosion resistance, high strength and self-lubrication, which gradually replace the traditional materials such as metal and ceramic in many special fields. SUMMARY

[0004] The purpose of the present application is to provide an ultra-thin large hollow lightweight speed reducer, which can meet the application requirements of small size, lightweight, high torque density and low vibration noise of the robot joint module.

[0005] The above technical purpose of the present application is realized by the following technical scheme:

[0006] An ultra-thin large hollow lightweight speed reducer, comprising a wave generator, a flexible bearing, a flexible wheel, a rigid wheel one and a rigid wheel two, the flexible bearing is sleeved outside the wave generator, the flexible wheel is sleeved outside the flexible bearing, the rigid wheel one and the rigid wheel two are sleeved outside the flexible wheel, and a connecting bearing is arranged between the rigid wheel one and the rigid wheel two, the inner teeth of the rigid wheel one and the rigid wheel two are respectively engaged with the outer teeth of the flexible wheel;

[0007] The wave generator is located at the center position of the flexible wheel in the axial direction, the axial length of the flexible wheel is not more than the total axial length of the rigid wheel one and the rigid wheel two; the number of the flexible bearing is 1-4, and the total axial length thereof is not more than the axial length of the flexible wheel; when the number of the flexible bearing is 1, it is located at the center position of the flexible wheel;

[0008] At least one of the wave generator, the flexible bearing, the flexible gear, the first rigid gear and the second rigid gear is made of engineering plastic; a ratio of an outer diameter of the speed reducer to a total axial length of the speed reducer is greater than 3:1, and a ratio of an inner hole diameter of the wave generator to the total axial length of the speed reducer is greater than 1:1;

[0009] The outer wall of the flexible gear is provided with a separation part located at a position of a gap between the first rigid gear and the second rigid gear, the separation part separates the outer teeth of the flexible gear into first meshing teeth and second meshing teeth, the first meshing teeth and the second meshing teeth have different tooth shapes; the first meshing teeth are engaged with the inner teeth of the first rigid gear by the same number of teeth or a different number of teeth, the second meshing teeth are engaged with the inner teeth of the second rigid gear by the same number of teeth or a different number of teeth, and the number of teeth difference between the first meshing teeth and the inner teeth of the first rigid gear and the number of teeth difference between the second meshing teeth and the inner teeth of the second rigid gear are different.

[0010] By adopting the above technical scheme, the hollow hole of the harmonic reducer in the prior art is often small due to the requirement of the structural strength of the harmonic reducer, the ratio of the hollow hole diameter to the axial length of the speed reducer is 1:3-1:2, for application occasions requiring a larger middle hole diameter, for example, a large number of wires, air pipes and cooling water pipes need to be arranged in the hollow hole of the existing robot joint module, under the premise of ensuring the structural strength, the harmonic reducer in the prior art cannot meet the requirements.

[0011] In the present application, the wave generator is arranged at the center position of the flexible gear in the axial direction, the axial length of the flexible gear does not exceed the total axial length of the first rigid gear and the second rigid gear, the number of flexible bearings is 1-4, and the total axial length thereof does not exceed the axial length of the flexible gear, and when the number of flexible bearings is 1, the flexible bearing is arranged at the center position of the flexible gear, so as to reduce the axial length of the speed reducer as much as possible, and at the same time, the outer diameter of the first rigid gear, the second rigid gear, the flexible gear, the flexible bearing and the wave generator can be increased, and the axial length of the first rigid gear, the second rigid gear, the flexible gear, the flexible bearing and the wave generator can be reduced, so as to realize the ultra-thin characteristic of the speed reducer. The axial length of the robot joint module is generally too long due to the arrangement of various parts such as the speed reducer, the motor, the brake, the encoder and the driving plate in the robot joint module, and the use of the ultra-thin speed reducer of the present application can shorten the axial length of the robot joint module as much as possible. In the present application, the ratio of the outer diameter of the speed reducer to the total axial length of the speed reducer is greater than 3:1, so as to ensure that the torsional rigidity and the bending rigidity of the speed reducer will not be weakened when the axial length of the speed reducer is reduced.

[0012] Meanwhile, the hole in the wave generator, i.e. the hole in the speed reducer, is correspondingly increased, the ratio of the hole diameter of the wave generator, i.e. the hole diameter of the speed reducer, to the total axial length of the speed reducer is greater than 1:1, so that the speed reducer is super-thin and large-hollow, which not only facilitates the arrangement of various wire conduits, reduces the wire length, and makes the cable less likely to be twisted and wound to cause accelerated damage, but also facilitates the connection of other components with the output end of the speed reducer. In addition, in the speed reducer, at least one part of the wave generator, the flexible bearing, the flexible gear, the first rigid gear and the second rigid gear is made of engineering plastic, so as to reduce the weight of the speed reducer and meet the application requirement of light weight.

[0013] In addition, in the prior art, when the flexible gear and the first rigid gear and the second rigid gear are engaged at the same time, one is engaged with the same number of teeth, and the other is engaged with different number of teeth, and the inner teeth of the first rigid gear and the inner teeth of the second rigid gear are two different tooth shapes, and the outer teeth of the flexible gear are single tooth shape in the axial direction, so that no matter what the tooth shape of the outer teeth of the flexible gear is, when the flexible gear is engaged with the first rigid gear and the second rigid gear, at least one of the two pairs of teeth cannot achieve the best engagement state, and there is a certain backlash between at least one pair of teeth, and since the first rigid gear and the second rigid gear have relative motion, two opposite forces are generated on the flexible gear, which results in a large discount in the performance of the speed reducer, such as engagement stiffness, backlash accuracy, transmission accuracy, noise and vibration.

[0014] In the present application, the outer teeth of the flexible gear are separated into first engagement teeth and second engagement teeth by the separation part, so as to avoid the mutual influence of the two different forces of the first rigid gear and the second rigid gear on the same section of the outer teeth of the flexible gear. Moreover, the first engagement teeth and the second engagement teeth have different tooth shapes, so that the first engagement teeth and the second engagement teeth can be designed separately according to the tooth shape of the inner teeth of the corresponding first rigid gear and second rigid gear, and the two sections of engagement can achieve their own optimal solution, so as to optimize the engagement effect of the flexible gear with the first rigid gear and the second rigid gear as a whole. In addition, the number of teeth of the first engagement teeth and the second engagement teeth can be the same or different, and the first rigid gear and the second rigid gear can be engaged with the same number of teeth or different number of teeth, as long as the number of teeth difference between the first engagement teeth and the inner teeth of the first rigid gear and the number of teeth difference between the second engagement teeth and the inner teeth of the second rigid gear are different. A larger or smaller reduction ratio can also be designed according to the different number of teeth difference between the first rigid gear, the second rigid gear and the flexible gear.

[0015] Further, the wave generator is provided with a separation groove corresponding to the separation part, and the cam shapes on both sides of the separation groove in the wave generator are different; the number of flexible bearings is at least 2, and the cams at both ends of the wave generator correspond to at least one flexible bearing respectively.

[0016] By adopting the technical scheme, the cam shape of the wave generator takes the separation groove as a boundary line, and is designed as a cam with different shapes at two ends, so as to further optimize the meshing effect of the first meshing tooth of the flexible gear and the inner tooth of the first rigid gear, and the second meshing tooth and the inner tooth of the second rigid gear. When the cam shapes at the two ends of the wave generator are different, there are at least two flexible bearings, and the cams at the two ends of the wave generator correspond to at least one flexible bearing respectively, so as to ensure the working effect.

[0017] Further, the separation part is a groove or a protrusion. When the separation part is the groove, the wall thickness of the flexible gear at the deepest part of the groove is not less than 0.1 mm. When the separation part is the protrusion, a displacement groove matched with the protrusion is arranged between the first rigid gear and the second rigid gear.

[0018] By adopting the technical scheme, the separation part is arranged as the groove or the protrusion, the outer tooth of the flexible gear is separated into the first meshing tooth and the second meshing tooth by the groove or the protrusion, and the mutual influence of the first rigid gear and the second rigid gear when meshing with the flexible gear is reduced. When the separation part is the groove, the groove part can play a certain buffering role when the speed reducer is impacted. The wall thickness of the flexible gear at the deepest part of the groove is not less than 0.1 mm, so as to avoid that the wall thickness at the deepest part of the groove is too small to affect the strength of the flexible gear. When the separation part is the protrusion, the protrusion can play a role of strengthening and reinforcing at the position where the force of the flexible gear is most concentrated, so as to prevent the corresponding position of the separation part from being twisted and deformed when the flexible gear is impacted, and improve the impact resistance of the speed reducer.

[0019] Further, at least one of the flexible gear, the first rigid gear and the second rigid gear is made of engineering plastic, and the cam shape of the wave generator is a polygon with a circular arc angle transition, and the flexible gear and the first rigid gear and the second rigid gear are two-point or multi-point meshing.

[0020] By adopting the technical scheme, the cam of the wave generator of the harmonic reducer in the prior art is mostly a 180° symmetrical double-convex structure, so that the meshing position of the flexible gear and the rigid gear is two-point meshing with 180° symmetry. This not only leads to that the number of meshing teeth of the flexible gear and the rigid gear is limited, and is usually 15%-25% of the total number of teeth, so as to cause that the rigidity of the harmonic reducer is not strong, but also the two-point support causes that the stability of the speed reducer is not strong, and when assembly eccentricity occurs or the input shaft is inclined or the speed reducer is impacted, the operating stability of the speed reducer is very poor.

[0021] If the flexible gear and the rigid gear are both made of metal, the wave generator is modified so that the flexible gear and the rigid gear are in multi-point engagement, and due to the limited deformation capacity of the material, it is difficult to ensure the smoothness of the engagement of the flexible gear and the rigid gear in the transition section between the multi-point engagement areas, and the reducer is prone to jamming. In the present application, at least one of the flexible gear, the first rigid gear and the second rigid gear is made of engineering plastic, and the shape of the wave generator is set as a polygon with a circular arc angle transition, so that the flexible gear, the first rigid gear and the second rigid gear can not only be in conventional 2-point engagement, but also be in 3-point, 4-point or even more than 4-point multi-point engagement, which can not only increase the total number of teeth or the total area of engagement, but also improve the stability of the reducer in operation.

[0022] Further, the engineering plastic is one or more of POM, PET, fiber-reinforced or modified PET, PA6, PA66, PES, PTFE, PPS, PAI, PEEK, fiber-reinforced or modified PEEK, and PI.

[0023] By adopting the above technical solution, at least one of the wave generator, the flexible bearing, the flexible gear, the first rigid gear and the second rigid gear is made of engineering plastic, providing multiple material options, which can be selected according to the actual application requirements, considering the production cost, service life, etc.

[0024] Further, the flexible gear is made of engineering plastic, and the wall thickness of the flexible gear is increased by 1-4 times, the tooth height of the outer teeth of the flexible gear is reduced by 10%-40%, and the tooth thickness is increased by 10%-50%.

[0025] By adopting the above technical solution, the flexible gear is made of engineering plastic, which has better flexibility and elasticity than metal, so the wall thickness of the flexible gear can be increased by 1-4 times compared with the thickness of the flexible gear in the same specification reducer in the prior art, thereby ensuring that the overall rigidity of the reducer will not be significantly reduced when the flexible gear is made of metal, and the flexibility of the flexible gear is increased, which can effectively improve the efficiency of the reducer. In addition, due to the better flexibility and elasticity of the flexible gear, the tooth height of the outer teeth of the flexible gear is reduced by 10%-40% and the tooth thickness is increased by 10%-50% compared with the outer teeth of the conventional flexible gear in the same type reducer in the prior art, thereby increasing the engagement strength of the outer teeth of the flexible gear and improving the torsional rigidity of the reducer.

[0026] Further, the flexible gear is made of PEEK with 5%-30% PTF added.

[0027] By adopting the above technical solution, the flexible gear is made of PEEK with 5%-30% PTF added, which can reduce the friction between the inner wall of the flexible gear and the outer wall of the flexible bearing, as well as the friction between the outer teeth of the flexible gear and the inner teeth of the two rigid gears, thereby reducing the noise and vibration of the reducer, improving the efficiency of the reducer, and prolonging the service life of the flexible gear and the flexible bearing.

[0028] Further, the inner wall of the flexible gear is nested with a PTFE ring, and the wall thickness of the PTFE ring is 0.2-1mm.

[0029] By adopting the above technical scheme, the PTFE ring is nested in the inner wall of the flexible gear to reduce the friction between the inner wall of the flexible gear and the outer wall of the outer ring of the flexible bearing, and the wall thickness of the PTFE ring is 0.2-1mm, so as to avoid unnecessary efficiency loss caused by the wall thickness of the PTFE ring being too large when the flexible bearing is deformed.

[0030] Further, the inner teeth of the rigid gear one and the rigid gear two are precisely processed after being injection molded into the metal material inner wall by engineering plastics.

[0031] By adopting the above technical scheme, the inner teeth of the rigid gear one and the rigid gear two are injection molded into the metal material inner wall by engineering plastics to form an integrated structure, and then the tooth part is precisely processed, so that the outer teeth of the rigid gear one and the rigid gear two engaged with the flexible gear are also made of engineering plastics, thereby further reducing the vibration and noise of the speed reducer.

[0032] Further, the rigid gear one and the rigid gear two are respectively used as the outer ring and the inner ring of the connecting bearing, the rigid gear one and the rigid gear two form an integrated structure with the connecting bearing, and the connecting bearing is one of a cross roller bearing, a four-point contact ball bearing or a double-row deep groove ball bearing.

[0033] By adopting the above technical scheme, the rigid gear one and the rigid gear two are respectively used as the outer ring and the inner ring of the connecting bearing, so that the connecting bearing is integrated with the rigid gear one and the rigid gear two, thereby further reducing the size and weight of the speed reducer. The connecting bearing is one of a cross roller bearing, a four-point contact ball bearing or a double-row deep groove ball bearing. The cross roller bearing has large bearing capacity, especially strong bending moment bearing capacity, and is usually made into negative clearance, so that the rotation precision is high, and the cross roller bearing is usually not suitable for high rotation speed. The double-row deep groove ball bearing can bear radial load and bidirectional axial load, and can be applied to higher rotation speed compared with the cross roller bearing, but the bearing capacity is relatively weak. The four-point contact ball bearing can also bear radial load and bidirectional axial load, and can be made into an ultra-thin structure to meet the lightweight requirement of the robot joint module, but the bearing capacity is also relatively weak compared with the cross roller bearing. The type of the connecting bearing can be selected according to the actual use requirement of the speed reducer to achieve the optimal performance.

[0034] In summary, the present application has the following advantages:

[0035] 1. In the application, the outer wall of the flexible gear is provided with a separation part separating the outer teeth into first meshing teeth and second meshing teeth, the first meshing teeth and the second meshing teeth have different tooth shapes, the first meshing teeth mesh with the first inner teeth of the first rigid gear or mesh with the first inner teeth of the first rigid gear with a difference in tooth number, the second meshing teeth mesh with the second inner teeth of the second rigid gear or mesh with the second inner teeth of the second rigid gear with a difference in tooth number, and the difference in tooth number between the first meshing teeth and the first inner teeth of the first rigid gear and the difference in tooth number between the second meshing teeth and the second inner teeth of the second rigid gear are different; in this way, the first meshing teeth and the second meshing teeth are designed separately according to the meshing condition of the corresponding first rigid gear and second rigid gear inner teeth, and both the two meshing can achieve their own optimal solution, thereby optimizing the meshing effect of the flexible gear and the first rigid gear and the second rigid gear as a whole; in addition, the tooth number of the first meshing teeth and the second meshing teeth can be the same or different, and the corresponding first rigid gear and second rigid gear can be the same number of teeth or a difference in tooth number, so that the speed reducer can be designed with a larger or smaller reduction ratio according to the difference in tooth number between the first rigid gear, the second rigid gear and the flexible gear;

[0036] 2. In the application, the wave generator is arranged at the center position of the flexible gear in the axial direction, the axial length of the flexible gear is consistent with the total axial length of the first rigid gear and the second rigid gear, the number of flexible bearings is 1-4, the total axial length of the flexible bearings does not exceed the axial length of the flexible gear, and when the number of flexible bearings is 1, the flexible bearings are also arranged at the center position of the flexible gear, so as to reduce the axial length of the speed reducer as much as possible, and at the same time, the outer diameter of the first rigid gear, the second rigid gear, the flexible gear, the flexible bearing and the wave generator can be increased, and the axial length of the first rigid gear, the second rigid gear, the flexible gear, the flexible bearing and the wave generator can be reduced, so as to realize the ultra-thin characteristics of the speed reducer, thereby reducing the axial length of the robot joint module as much as possible; wherein, the ratio of the outer diameter of the speed reducer to the total axial length of the speed reducer is greater than 3:1, so as to ensure that the torsional rigidity and bending rigidity of the speed reducer will not be weakened when the axial length of the speed reducer is reduced; at the same time, the inner hole of the wave generator, i.e. the middle hole of the speed reducer, is correspondingly increased, the ratio of the inner hole diameter of the wave generator to the total axial length of the speed reducer is greater than 1:1, so that the speed reducer achieves ultra-thin and large hollow, which not only facilitates the arrangement of various wire pipes and reduces the wire length, so that the cable is not easy to twist and wind to cause accelerated damage, but also facilitates the connection of other components with the output end of the speed reducer;

[0037] 3. At least one part of the wave generator, the flexible bearing, the flexible gear, the first rigid gear and the second rigid gear in the application is made of engineering plastic, so as to reduce the weight of the speed reducer and meet the application requirements of lightweight;

[0038] 4. In the application, the flexible gear is made of engineering plastic, the wall thickness of the flexible gear is increased by 1-4 times, the tooth height of the outer teeth of the flexible gear is reduced by 10%-40%, and the tooth thickness is increased by 10%-50%, so as to ensure that the overall rigidity of the speed reducer will not be significantly reduced compared with the flexible gear made of metal, and the flexible resistance can be reduced after the flexibility of the flexible gear is increased, so as to effectively improve the efficiency of the speed reducer, increase the meshing strength of the outer teeth of the flexible gear, and improve the torsional rigidity of the speed reducer;

[0039] 5、The wave generator in the application is a polygon with a circular arc angle transition, the flexible gear and the first and second rigid gears are two-point or multi-point meshing, the number of meshing teeth or the total meshing area of the flexible gear and the first and second rigid gears is increased, so that the reducer is prevented from being easily jammed during operation, and the stability and efficiency of the reducer operation are improved;

[0040] 6、The flexible gear in the application is made of engineering plastic, and has better deformation capacity when subjected to abnormal meshing force, can realize interference avoidance in the axial direction, thereby greatly reducing the vibration and noise of the reducer, and the noise of the reducer under rated torque and rated speed is less than 45 decibels within 1 meter distance;

[0041] 7、The reducer of the application has the characteristics of ultra-thin, ultra-light, large hollow hole, etc., and can meet the application requirements of small size, light weight, high torque density and low vibration noise of the robot joint module. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 It is a whole structure schematic diagram of the ultra-thin large hollow lightweight reducer when the partition part is a groove and the connecting bearing is a cross roller bearing;

[0043] Figure 2 It is a whole structure schematic diagram of the ultra-thin large hollow lightweight reducer when the partition part is a protrusion;

[0044] Figure 3 It is a whole structure schematic diagram of the ultra-thin large hollow lightweight reducer when the cam shapes at both ends of the wave generator are different;

[0045] Figure 4 It is a structure schematic diagram of the wave generator when the cam shapes at both ends of the wave generator are different in the ultra-thin large hollow lightweight reducer

[0046] Figure 5 It is a whole structure schematic diagram of the ultra-thin large hollow lightweight reducer when the inner teeth of the first and second rigid gears are made of engineering plastic;

[0047] Figure 6 It is a modification schematic diagram of the outer teeth of the flexible gear in the ultra-thin large hollow lightweight reducer;

[0048] Figure 7 It is a schematic diagram of the flexible gear and the first rigid gear in two-point meshing in the ultra-thin large hollow lightweight reducer;

[0049] Figure 8 It is a schematic diagram of the flexible gear and the first rigid gear in three-point meshing in the ultra-thin large hollow lightweight reducer;

[0050] Figure 9This is a schematic diagram of the flexure and rigid wheel meshing at four points in an ultra-thin, large, hollow, lightweight reducer.

[0051] Figure 10 This is a schematic diagram of the overall structure of an ultra-thin, large, hollow, lightweight speed reducer when the connecting bearing is a four-point contact ball bearing.

[0052] Figure 11 This is a schematic diagram of the overall structure of an ultra-thin, large, hollow, lightweight speed reducer where the connecting bearing is a double-row deep groove ball bearing.

[0053] In the figure, 1 is the wave generator; 11 is the partition groove; 2 is the flexible bearing; 3 is the flexible wheel; 31 is the partition part; 32 is the first meshing tooth; 33 is the second meshing tooth; 34 is the PTFE ring; 4 is the first rigid wheel; 5 is the second rigid wheel; and 6 is the connecting bearing. Detailed Implementation

[0054] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0055] An ultra-thin, large hollow, lightweight speed reducer, such as Figure 1 As shown, the reducer includes a wave generator 1, a flexible bearing 2, a flexure wheel 3, a first rigid wheel 4, and a second rigid wheel 5. The flexible bearing 2 is mounted outside the wave generator 1, the flexure wheel 3 is mounted outside the flexible bearing 2, and the first rigid wheel 4 and the second rigid wheel 5 are mounted outside the flexure wheel 3. A connecting bearing 6 is provided between the first rigid wheel 4 and the second rigid wheel 5. The internal teeth of the first rigid wheel 4 and the second rigid wheel 5 respectively mesh with the external teeth of the flexure wheel 3. The basic structure and working principle of the reducer in this invention are the same as those of the existing double rigid wheel harmonic reducer, and will not be described in detail.

[0056] like Figure 1 As shown, the wave generator 1 is located at the center of the flexible wheel 3 in the axial direction. The axial length of the flexible wheel 3 does not exceed the total axial length of the rigid wheel 4 and the rigid wheel 5. The number of flexible bearings 2 is 1-4, and their total axial length does not exceed the axial length of the flexible wheel 3. In this embodiment, the axial length of the flexible wheel 3 is consistent with the total axial length of the rigid wheel 4 and the rigid wheel 5. The number of flexible bearings 2 is one, and it is located at the center of the flexible wheel 3 in the axial direction. The axial length of the flexible wheel 3 is slightly greater than the axial length of the flexible bearing 2. In other embodiments, when there is only one flexible bearing 2, its axial length can also be equal to the axial length of the flexible wheel 3.

[0057] Due to the structural strength requirements, the hollow holes in existing harmonic reducers are often small, with the ratio of the hollow hole diameter to the axial length of the reducer being 1:3 to 1:2. For applications requiring larger hollow hole diameters, such as existing robot joint modules that need to run a large number of wires, air pipes, and cooling water pipes through the hollow holes, existing harmonic reducers cannot meet the requirements while ensuring structural strength.

[0058] Therefore, as Figure 1 As shown, in order to minimize the axial length of the reducer without weakening its torsional and bending rigidity, the outer diameters of the rigid wheel 4, rigid wheel 5, flexible wheel 3, flexible bearing 2, and wave generator 1 are appropriately increased, while the inner diameter of the wave generator 1 is also enlarged. Specifically, the ratio of the reducer's outer diameter to its total axial length is greater than 3:1, and the ratio of the reducer's hollow diameter to its total axial length is greater than 1:1. This gives the reducer an ultra-thin structure and a large central hole, which not only facilitates the arrangement of various wires and pipes, reduces cable length, and prevents cables from twisting and tangling, thus reducing accelerated damage, but also facilitates the connection of other components to the reducer's output end.

[0059] In this embodiment, the outer diameters of the first rigid wheel 4 and the second rigid wheel 5 are equal, representing the outer diameter of the reducer. The axial length of the flexible wheel 3 is consistent with the total axial length of the first rigid wheel 4 and the second rigid wheel 5, representing the axial length of the reducer. The inner diameter of the wave generator 1 represents the hollow diameter of the reducer. Therefore, it can be considered that the ratio of the outer diameter of the first rigid wheel 4 to the axial length of the flexible wheel 3 is greater than 3:1, and the ratio of the inner diameter of the wave generator 1 to the axial length of the flexible wheel 3 is greater than 1:1. Of course, in other embodiments, when the largest outer diameter of the first rigid wheel 4 and the second rigid wheel 5 represents the outer diameter of the reducer, and the axial length of the flexible wheel 3 is less than the total axial length of the first rigid wheel 4 and the second rigid wheel 5, the total axial length of the first rigid wheel 4 and the second rigid wheel 5 represents the total axial length of the reducer.

[0060] In the existing technology, when the flexible wheel meshes with rigid wheel one and rigid wheel two simultaneously, one of them is meshed with the same number of teeth, while the other is meshed with a difference of 2 teeth. Moreover, the internal teeth of rigid wheel one and rigid wheel two have two different tooth profiles, while the external teeth of the flexible wheel are a single tooth profile that penetrates axially. Therefore, regardless of the tooth profile of the external teeth of the flexible wheel, when it meshes with rigid wheel one and rigid wheel two, at least one of the two pairs of teeth will inevitably fail to achieve the optimal meshing state, and there will be a certain backlash between at least one pair of meshing teeth. Furthermore, due to the relative motion between rigid wheel one and rigid wheel two, two forces with opposite directions will be generated on the flexible wheel. This leads to a significant reduction in various performance aspects of the reducer, such as meshing stiffness, backlash accuracy, transmission accuracy, noise, and vibration.

[0061] Therefore, as Figure 1 or Figure 2As shown, the present application is provided with a partition 31 on the outer wall of the flexible gear 3, which is located in the gap between the rigid gear one 4 and the rigid gear two 5. The partition 31 separates the outer teeth of the flexible gear 3 into the first meshing teeth 32 and the second meshing teeth 33, and the first meshing teeth 32 and the second meshing teeth 33 have different tooth shapes, and the number of teeth can be the same or different. Specifically, the first meshing teeth 32 are engaged with the inner teeth of the rigid gear one 4 with the same number of teeth or with a different number of teeth, and the second meshing teeth 33 are engaged with the inner teeth of the rigid gear two 5 with the same number of teeth or with a different number of teeth, and the difference between the number of teeth of the first meshing teeth 32 and the inner teeth of the rigid gear one 4 and the difference between the number of teeth of the second meshing teeth 33 and the inner teeth of the rigid gear two 5 are different.

[0062] In this way, the first meshing teeth 32 and the second meshing teeth 33 can be designed separately according to the meshing condition of the inner teeth of the corresponding rigid gear one 4 and the rigid gear two 5, so that the two sections of meshing achieve their own optimal solution, thereby optimizing the meshing effect of the flexible gear 3 and the rigid gear one 4 and the rigid gear two 5 as a whole. In addition, different tooth number differences between the rigid gear one 4, the rigid gear two 5 and the flexible gear 3 can be used to design a larger or smaller reduction ratio for the speed reducer.

[0063] In addition, as shown in Figure 3 and Figure 4 , the wave generator 1 is provided with a partition groove 11 corresponding to the partition 31, and the wave generator 1 is designed as a cam with different shapes at both ends with the partition groove 11 as the boundary, to further optimize the meshing effect of the first meshing teeth 32 of the flexible gear 3 and the inner teeth of the rigid gear one 4, and the second meshing teeth 33 and the inner teeth of the rigid gear two 5. At this time, the number of flexible bearings 2 should be at least two, and the cams at both ends of the wave generator 1 should correspond to at least one flexible bearing 2 respectively. Among them, the partition groove 11 is used as the boundary of the cams with different shapes at both ends of the wave generator 1, and the partition groove 11 is convenient to process, and in other embodiments, the partition groove 11 is replaced by a protrusion or a partition gap.

[0064] In this embodiment, as shown in Figure 1 and Figure 2 , the partition 31 can be a groove or a protrusion. As shown in Figure 1 , when the partition 31 is a groove, not only can the groove separate the outer teeth of the flexible gear 3 into the first meshing teeth 32 and the second meshing teeth 33, reducing the mutual influence of the rigid gear one 4 and the rigid gear two 5 when they mesh with the flexible gear 3, but also the groove part can play a certain buffering role when the speed reducer is impacted. Among them, the wall thickness of the flexible gear 3 at the deepest part of the groove position should not be less than 0.1mm, to avoid that the wall thickness of the flexible gear 3 at the groove position is too small to affect the strength of the flexible gear 3.

[0065] As shown in Figure 2As shown, when the partition 31 is a protrusion, not only can the soft gear 3 outer teeth be separated into two parts of the first meshing tooth 32 and the second meshing tooth 33 by the protrusion, reducing the mutual influence when the rigid gear one 4 and the rigid gear two 5 mesh with the soft gear 3 respectively, but also the protrusion can play a role in strengthening and reinforcing at the part where the force of the soft gear 3 is most concentrated, preventing the soft gear 3 from being distorted at the corresponding position of the partition 31 when impacted, and improving the impact resistance of the speed reducer. Among them, a give-way groove cooperating with the protrusion is arranged between the rigid gear one 4 and the rigid gear two 5 to avoid interference between the protrusion and the rigid gear one 4 or the rigid gear two 5. Of course, in other embodiments, the partition 31 can also be a space gap between the first meshing tooth 32 and the second meshing tooth 33 close to one end.

[0066] In the present application, in order to reduce the overall weight of the speed reducer, at least one of the wave generator 1, the flexible bearing 2, the soft gear 3, the rigid gear one 4 and the rigid gear two 5 is made of engineering plastic, and the engineering plastic can be one or more of POM, PET, fiber-reinforced or modified PET, PA6, PA66, PES, PTFE, PPS, PEEK, fiber-reinforced or modified PEEK, PI, greatly reducing the weight of the speed reducer, and greatly reducing the conduction of motor heat to the speed reducer, avoiding high-temperature operation of the speed reducer. Of course, in other embodiments, the wave generator 1 can also be made of high-strength and low-density metal materials such as aluminum or aluminum alloy.

[0067] In the present embodiment, the soft gear 3 is made of PEEK with 5%-30% PTF added, and since the engineering plastic material has a self-lubricating effect, the use of lubricating oil can be greatly reduced or even eliminated, thereby completely avoiding the risk of oil leakage of the speed reducer, and also reducing the friction between the inner wall of the soft gear 3 and the outer wall of the flexible bearing 2, as well as the friction between the outer teeth of the soft gear 3 and the inner teeth of the rigid gear one 4 and the rigid gear two 5, thereby reducing the vibration of the speed reducer, improving the efficiency of the speed reducer, and prolonging the service life of the soft gear 3 and the flexible bearing 2. Among them, as shown in the figure, Figure 1 In the present embodiment, a PTFE ring 34 is nested in the inner wall of the soft gear 3, and the wall thickness of the PTFE ring 34 is 0.2-1mm, which further reduces the friction between the inner wall of the soft gear 3 and the outer wall of the flexible bearing 2.

[0068] As shown in the figure, Figure 5 In the present embodiment, the rigid gear one 4 and the rigid gear two 5 can also be made of engineering plastic inner teeth that are injection molded on the inner wall of the metal material and then finished, further reducing the vibration and noise of the speed reducer, and the tooth gap between the engineering plastic inner teeth and the soft gear 3 is smaller than the tooth gap between the steel inner teeth and the soft gear 3.

[0069] The flexible gear 3 is not fixed and can freely move in the axial direction, and the flexible gear 3 is made of engineering plastic, and has better deformation capacity when subjected to abnormal meshing force, and can achieve good interference avoidance in the free space in the axial direction, so that the vibration and noise of the speed reducer can be greatly reduced, and the noise of the speed reducer under the rated torque and rated speed is less than 45 decibels per meter.

[0070] In addition, the wall thickness of the flexible gear of the small harmonic speed reducer in the prior art is between 0.5-1mm, and the wall thickness of the flexible gear of the large and medium harmonic speed reducer is in the range of 1.5-2.0mm, and the flexible gear 3 in the present application is made of engineering plastic, which has better flexibility and elasticity than metal, so the wall thickness of the flexible gear 3 can be increased by 1-4 times. When the wall thickness of the flexible gear 3 increases, the overall rigidity of the speed reducer will not be significantly reduced compared to when the flexible gear 3 is made of metal, and the increase in flexibility of the flexible gear 3 can reduce the flexible resistance, thereby improving the efficiency of the speed reducer.

[0071] As shown in Figure 6 , in the prior art, the tooth height h1 of the conventional flexible gear is about 0.3-1mm, and the tooth thickness s1 is about 0.3-1mm. In the present application, the flexible gear 3 made of engineering material has better deformation capacity, so the outer teeth of the flexible gear 3 can be shaped, the tooth height of the outer teeth of the flexible gear 3 is reduced by 10%-40%, and the tooth thickness is increased by 10%-50%, that is, the tooth height h2 of the outer teeth of the flexible gear 3 in the present application is about 0.6-0.9 times the tooth height h1 of the conventional flexible gear corresponding to the same type of harmonic speed reducer, and the tooth thickness s2 of the outer teeth of the flexible gear 3 in the present application is about 1.1-1.5 times the tooth thickness s1 of the conventional flexible gear corresponding to the same type of harmonic speed reducer. In this way, the meshing strength of the outer teeth of the flexible gear 3 and the inner teeth of the rigid gear 4 and the rigid gear 5 is increased, and the torsional rigidity of the speed reducer is improved.

[0072] As shown in Figure 7 , in the prior art, the wave generator cam of the harmonic speed reducer is mostly a 180° symmetrical double convex structure, so that the meshing part of the flexible gear and the rigid gear is two-point meshing with 180° symmetry, which not only leads to limited meshing teeth of the flexible gear and the rigid gear, usually 15%-25% of the total number of teeth, thereby resulting in poor rigidity of the harmonic speed reducer; and two-point support makes the stability of the speed reducer not strong, when the assembly eccentricity occurs or the input shaft is inclined or the speed reducer is impacted, the running stability of the speed reducer is very poor. If the flexible gear and the rigid gear are both made of metal, when the flexible gear and the rigid gear are shaped to mesh at multiple points, due to the limited deformation capacity of the material, it is difficult to ensure the smoothness of the meshing of the flexible gear and the rigid gear in the transition section between the multiple meshing regions, and the speed reducer is prone to jamming during operation.

[0073] And at least one of the flexible gear 3, the rigid gear one 4 and the rigid gear two 5 is made of engineering plastic, which has better flexibility and elasticity, and the flexible gear 3 has greater ability to avoid interference when engaging with the rigid gear one 4 and the rigid gear two 5, so the shape of the cam of the wave generator 1 can have more design possibilities. Figure 7 、 Figure 8 and Figure 9 As shown in the application, the shape of the wave generator 1 (marked in Figure 1 ) is a circular arc angle transition polygon, the flexible gear 3 and the rigid gear one 4 and the rigid gear two 5 are 2-point engagement as shown in Figure 7 , or 3-point engagement as shown in Figure 8 , or 4-point engagement as shown in 4, the multi-point engagement of the flexible gear 3 and the rigid gear one 4 and the rigid gear two 5 not only can increase the total number of teeth or the total area of engagement, but also can avoid jamming and improve the stability of the operation of the speed reducer. Of course, when the cam shapes at both ends of the wave generator 1 are different, the number of engagement points of the flexible gear 3 and the rigid gear one 4 and the rigid gear two 5 can be the same or different.

[0074] In the application, in order to further reduce the weight of the speed reducer, as shown in Figure 1 、 Figure 10 and Figure 11 , the rigid gear one 4 and the rigid gear two 5 are respectively connected to the outer ring and the inner ring of the connecting bearing 6, so that the rigid gear one 4, the rigid gear two 5 and the connecting bearing 6 form an integrated structure. Among them, the connecting bearing 6 is one of a cross roller bearing, a four-point contact ball bearing or a double-row deep groove ball bearing.

[0075] As shown in Figure 1 , the connecting bearing 6 is a cross roller bearing, which has large bearing capacity, especially strong bending moment bearing capacity, and is usually made into negative clearance, high rotation accuracy, and is not usually suitable for high speed. As shown in Figure 10 , the connecting bearing 6 is a four-point contact ball bearing, which can bear radial load and bidirectional axial load, can be made into an ultra-thin structure, and can meet the lightweight demand of the robot joint module, but the bearing capacity is relatively weak compared with the cross roller bearing. As shown in Figure 11 , the connecting bearing is a double-row deep groove ball bearing, which can bear radial load and bidirectional axial load, and can be applied to higher speed compared with the cross roller bearing, but the bearing capacity is relatively weak. The type of the connecting bearing 6 can be selected according to the actual use occasion of the speed reducer to achieve the best performance.

[0076] The foregoing description has shown and described preferred embodiments of the application, but it will be understood that the application is not limited to the particular embodiments shown and described, as such will have many modifications, permutations, additions and subtractions and changes as are obvious to one skilled in the art, and it is therefore intended to cover all such modifications and changes as fall within the scope of the application, including combinations of the various features described above. Changes and modifications can be made to the application in light of this teaching and it is therefore intended to cover in the appended claims all such changes and modifications that fall within the scope of the application.

Claims

1. An ultra-thin large-hollow lightweight speed reducer, characterized by: The reducer comprises a wave generator (1), a flexible bearing (2), a flexible gear (3), a rigid gear I (4) and a rigid gear II (5), the flexible bearing (2) is sleeved outside the wave generator (1), the flexible gear (3) is sleeved outside the flexible bearing (2), the rigid gear I (4) and the rigid gear II (5) are sleeved outside the flexible gear (3), a connecting bearing (6) is arranged between the rigid gear I (4) and the rigid gear II (5), and inner teeth of the rigid gear I (4) and the rigid gear II (5) are respectively engaged with outer teeth of the flexible gear (3); The wave generator (1) is located at a central position of the flexible gear (3) in an axial direction, an axial length of the flexible gear (3) is not more than a total axial length of the rigid gear I (4) and the rigid gear II (5), the number of the flexible bearing (2) is 1-4, and an axial total length of the flexible bearing (2) is not more than the axial length of the flexible gear (3); when the number of the flexible bearing (2) is 1, the flexible bearing (2) is located at the central position of the flexible gear (3); At least one of the wave generator (1), the flexible bearing (2), the flexible gear (3), the rigid gear I (4) and the rigid gear II (5) is made of engineering plastic; a ratio of an outer diameter of the reducer to a total axial length of the reducer is greater than 3:1, and a ratio of a hole diameter of the wave generator (1) to the total axial length of the reducer is greater than 1:1; An outer wall of the flexible gear (3) is provided with a separation part (31) located at a gap position between the rigid gear I (4) and the rigid gear II (5), the separation part (31) separates the outer teeth of the flexible gear (3) into first engagement teeth (32) and second engagement teeth (33), the first engagement teeth (32) and the second engagement teeth (33) are different in tooth shape, the first engagement teeth (32) are engaged with the inner teeth of the rigid gear I (4) in the same number of teeth or different number of teeth, the second engagement teeth (33) are engaged with the inner teeth of the rigid gear II (5) in the same number of teeth or different number of teeth, and the number of teeth difference between the first engagement teeth (32) and the inner teeth of the rigid gear I (4) and the number of teeth difference between the second engagement teeth (33) and the inner teeth of the rigid gear II (5) are different; The wave generator (1) is provided with a separation groove (11) corresponding to the separation part (31), and cam shapes of two sides of the separation groove (11) in the wave generator (1) are different; the number of the flexible bearing (2) is at least two, and the cams at two ends of the wave generator (1) correspond to at least one flexible bearing (2) respectively; At least one of the flexible gear (3), the rigid gear I (4) and the rigid gear II (5) is made of engineering plastic, and a cam shape of the wave generator (1) is a polygon with a circular arc angle transition, the flexible gear (3) is engaged with the rigid gear I (4) and the rigid gear II (5) in two-point or multi-point; The flexible gear (3) is made of engineering plastic, and a wall thickness of the flexible gear (3) is increased by 1-4 times, a tooth height of the outer teeth of the flexible gear (3) is reduced by 10%-40%, and a tooth thickness is increased by 10%-50%.

2. The ultra-thin large hollow lightweight speed reducer according to claim 1, characterized in that: The separation part (31) is a groove or a protrusion, when the separation part (31) is the groove, a wall thickness of the flexible gear (3) at a deepest position of the groove is not less than 0.1 mm, and when the separation part (31) is the protrusion, a giving-up groove matched with the protrusion is arranged between the rigid gear I (4) and the rigid gear II (5).

3. The ultra-thin large hollow lightweight speed reducer according to claim 1, characterized in that: The engineering plastic is one or more of POM, PET, fiber-reinforced or modified PET, PA6, PA66, PES, PTFE, PPS, PAI, PEEK, fiber-reinforced or modified PEEK, and PI.

4. The ultra-thin large hollow lightweight speed reducer according to claim 1, characterized in that: The flexible gear (3) is made of PEEK with 5%-30% PTFE added.

5. The ultra-thin large hollow lightweight speed reducer according to claim 1, characterized in that: The inner wall of the flexible gear (3) is nested with a PTFE ring (34), and the wall thickness of the PTFE ring (34) is 0.2-1 mm.

6. The ultra-thin large hollow lightweight speed reducer according to claim 1, characterized in that: The inner teeth of the rigid gear one (4) and the rigid gear two (5) are made by precision machining after the engineering plastic is injection molded in the metal material inner wall.

7. The ultra-thin large hollow lightweight speed reducer according to claim 1, characterized in that: The rigid gear one (4) and the rigid gear two (5) are respectively used as the outer ring and the inner ring of the connecting bearing (6), the rigid gear one (4) and the rigid gear two (5) form an integrated structure with the connecting bearing (6), and the connecting bearing (6) is one of a cross roller bearing, a four-point contact ball bearing, or a double-row deep groove ball bearing.

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