Distributed K-H-V type involute small tooth difference joint module

Abstract

The invention discloses a distributed K-H-V type involute joint module with a small tooth difference. The distributed K-H-V type involute joint module is applied to a joint on a snakelike mechanical arm. The joint module is composed of three sets of rotary driving units, a rack, an inner gear and an outer gear, in the transmission process, the eccentric shaft rotates to drive the inner gear to output at the rotating speed, and then the outer gear translates. The three groups of rotary driving units are respectively mounted in through holes formed in the inner gear and the outer gear at equal intervals; the rotary driving unit is matched with a bearing, an outer gear and an inner gear through a small motor, so that the space utilization rate of the joint module is increased; and in addition, by reducing transmission links, the power loss of the joint module is reduced, so that the joint module has the characteristics of small size and high output efficiency on the basis of having the characteristics of high rigidity and large transmission ratio of involute small tooth difference planetary gear transmission.

Description

Technical Field

[0001] The present invention relates to an improvement on a joint module used on a snake-like robot arm, and more particularly, to a distributed KHV type involute small-tooth-difference joint module. Background Art

[0002] In the 1920s, Petr Miturich first proposed the concept of a snake-like robot arm. He believed that mechanical devices could simulate the movement of snakes to obtain more efficient gaits, such as spring movement, sinusoidal movement, and lateral rotation. Although the snake-like robot arm was designed earlier, it was limited by the weak theory of motion models used for motion planning at the time. Until the 1980s, the coordinated control of the snake-like arm morphology was still a difficult problem. With the gradual improvement of the theory, after the 1990s, the snake-like robot arm entered a period of rapid development. Due to its high degree of freedom, flexible movement, and large aspect ratio, it is suitable for various narrow, complex, deep cavity, and sealed environments. It has gradually been used in assembly manufacturing and surveying and maintenance in the fields of aerospace and nuclear power plants; active endoscopes in the medical field, various types of minimally invasive surgery, and controllable needle technology.

[0003] The joint module is a highly integrated modular joint with an integrated design. It is a mechanism for relative movement between the various parts of the robot, which can quickly achieve the functional requirements and practical goals of the robot. The joint module is often used for rope drive of snake-like robotic arms, as well as joint drive of humanoid and quadruped robots.

[0004] At present, joint modules can be roughly divided into two categories. One is cylindrical, and mostly uses a hollow torque motor plus a harmonic reducer. Its overall length is large, and the harmonic reducer is costly, has poor rigidity, is not impact-resistant, and has low transmission efficiency. It is not suitable for the leg joints of quadruped and humanoid robots. The other is disc-shaped, and mostly uses a hollow torque motor plus a planetary reducer. Its appearance is more suitable for leg joints, but the planetary reducer is inside the motor, its transmission is relatively small, and the planetary gear transmission has backlash and low precision.

[0005] When the output of the serpentine robot drive unit is rotational motion, harmonic, planetary and other reducers are often used to increase the torque. In-depth research has found that the involute small tooth difference gear transmission is also suitable for the serpentine robot drive unit due to its large transmission ratio, compact structure, reliable operation, high overload and impact resistance, especially the 2K-H and KHV types. Therefore, the research on the involute small tooth difference gear transmission has certain practical significance for the serpentine robot drive unit.

[0006] The so-called small tooth difference refers to a pair of KHV type planetary gear transmissions with a small difference in the number of teeth, usually consisting of an involute internal meshing gear pair with a difference in the number of teeth of 1 to 4. This transmission device consists of a central wheel (internal gear K), a planet carrier (eccentric shaft H) and a special output mechanism V. It is named KHV type according to its basic components: it is named N type according to its meshing mode, and N means internal meshing. There is also a 2K-H type double internal meshing small tooth difference planetary transmission, whose basic components are two central wheels K and a planet carrier (eccentric shaft H), and it is named NN type double internal meshing gear pair according to its meshing mode. Summary of the invention

[0007] In order to realize the requirements of the serpentine robot arm for the large torque, high precision, and small volume of the joint module, as well as the requirements for the flattening of the joint module, the present invention adopts an involute small-tooth difference planetary gear transmission as a reducer, which has a large transmission ratio. On the basis of the traditional KHV type, a configuration innovation is carried out, and a distributed KHV type transmission is designed, and three small motors are used to replace a large motor, and the three small motors are distributed in the middle of the outer gear, so that the joint module structure space utilization rate is higher, and the multi-stage transmission link is reduced, and the first-level sliding friction is converted into rolling friction, which improves the transmission efficiency. The present invention designs a distributed KHV type involute small-tooth difference joint module with a small volume, disc shape, high rigidity, high precision, and large transmission ratio through an innovative transmission mode and an integrated design of the motor and the transmission system.

[0008] The present invention discloses a distributed KHV-type involute small-tooth-difference joint module applied to a serpentine robot arm, comprising a first rotation drive unit (1), a second rotation drive unit (2), a third rotation drive unit (3), an internal gear (4), a frame (5), a uniform-section thin-walled bearing (6), a first gear cover (41), a second gear cover (61), a first external gear (7), and a second external gear (8);

[0009] Wherein, the first rotation drive unit (1), the second rotation drive unit (2) and the third rotation drive unit (3) have the same structure;

[0010] Wherein, the first gear cover (41) and the second gear cover (61) have the same structure;

[0011] The first external gear (7) and the second external gear (8) have the same structure; the GA panel (71) of the first external gear (7) is provided with a stepped through hole for placing a bearing, and the GB panel (72) of the first external gear (7) is a smooth surface;

[0012] The D-axis center hole (41F) of the first gear cover (41), the G-axis center hole (7E) of the first external gear (7), the H-axis center hole (8E) of the second external gear (8) and the F-axis center hole (61F) of the second gear cover (61) are aligned and kept coaxial;

[0013] Wherein, the frame (5) and the internal gear (4) are kept coaxial;

[0014] The first rotation drive unit (1) comprises a DC brushless motor (1A), an eccentric shaft cover plate (1B), an AA deep groove ball bearing (1C), an AB deep groove ball bearing (1D), an A reverse retaining spring (1E), an eccentric shaft (1F) and an A shaft ring (1G); the motor output shaft (1A1) of the motor (1A) sequentially passes through the AB center through hole (1F1) of the A eccentric shaft (1F), the AA center through hole (1F1) of the A eccentric shaft cover plate (1B) and the AB center through hole (1F2) of the A eccentric shaft (1F). hole (1B1); the A eccentric shaft (1F) and the A eccentric shaft cover plate (1B) are fixed to the front end cover of the motor (1A) by screws; the AA shaft section (1F7) of the A eccentric shaft (1F) is installed with an AA deep groove ball bearing (1C), the AB shaft section (1F8) is installed with an AB deep groove ball bearing (1D), the AC shaft section (1F9) is installed with an A shaft ring (1G), and the retaining groove (1F10) is installed with an A reverse retaining ring (1E);

[0015] The inner ring surface of the internal gear (4) is provided with D inner teeth (4A), D inner convex ring (4C) and D bearing section (4B) in sequence; the D inner convex ring (4C) is used to block and limit the movement of the uniform cross-section thin-walled bearing (6) in the up and down directions; the outer ring of the uniform cross-section thin-walled bearing (6) is connected to the D bearing section (4B) of the internal gear (4); the inner ring of the uniform cross-section thin-walled bearing (6) is connected to the E bearing section (5F) of the frame (5); the D inner teeth (4A) of the internal gear (4) are used to mesh with the G outer teeth (7D) on the first outer gear (7) and the H outer teeth (8D) on the second outer gear (8);

[0016] The joint module uses two external gears (7, 8) of the same structure and are placed symmetrically relative to the central axis of the internal gear (4). When moving, the eccentricity is equal in size and opposite in direction, and they cancel each other out.

[0017] Compared with the existing KHV type (pin-type) joint module technology, the advantages of the distributed KHV type involute small tooth difference joint module of the present invention are:

[0018] (1) Structural volume: The distributed KHV reduces the multi-stage transmission links including sliding friction. The compact structure has a smaller volume. The motor is inside the gear, which effectively utilizes the space. The number of parts in the structure is smaller, the structure is simpler, and the processing and assembly are more convenient.

[0019] (2) Transmission ratio. Calculated using the transmission ratio formula, the transmission ratio is related to the number of teeth on the outer gear and the difference in the number of teeth between the inner and outer gears. The difference in the number of teeth has a greater impact. The smaller the difference in the number of teeth, the larger the transmission ratio. The calculation results show that the distributed KHV has a large transmission ratio. Due to the large transmission ratio, the motor can maintain a high speed, with higher transmission efficiency and greater output power. A transmission ratio of 100 or even higher can be achieved by using a single-stage transmission; if a three-stage transmission is used, a transmission ratio of more than 10,000 can be achieved.

[0020] (3) In the distributed KHV mechanism, except for gear meshing, there is no high pair and no sliding friction, which has lower power loss than the KHV type (pin type). The redundancy is high, and the degree of freedom of the joint module is 1. Only one power source needs to be retained to control the movement of the mechanism.

[0021] (4) The power source can be split and evenly arranged in the equally divided holes of the external gear, which can make full use of the space and make the overall size of the joint module smaller. The distributed KHV structure is flattened, making the drive not only suitable for the drive of snake-like robotic arms, but also suitable for the joints of humanoid and quadruped robots, and the application scenarios are richer.

[0022] (5) Involute gear transmission has lower processing cost than cycloidal pinwheel and can be processed in batches using traditional gear processing methods.

[0023] (6) High reliability. The three motors are parallel output, but as long as one motor is operating normally, the entire system can output at the original speed, and the output torque will decrease. The power upper limit is higher. The torque of the power sources evenly arranged in the equally divided holes of the external gear can be accumulated together, but the synchronization requirements of each power source are high. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural diagram of the distributed KHV type involute small tooth difference joint module of the present invention.

[0025] Figure 1A This is another perspective structural diagram of the distributed KHV type involute small tooth difference joint module of the present invention.

[0026] Figure 1B It is a cross-sectional structural diagram of the distributed KHV type involute small tooth difference joint module of the present invention.

[0027] Figure 1C This is a cross-sectional structural diagram from another perspective of the distributed KHV type involute small-tooth difference joint module of the present invention.

[0028] Figure 1D It is an exploded view of the distributed KHV type involute small tooth difference joint module of the present invention.

[0029] Figure 2 It is a cross-sectional structural diagram of the first rotary drive unit in the distributed KHV type involute small-tooth difference joint module of the present invention.

[0030] Figure 2A It is an exploded view of the first rotation drive unit of the present invention.

[0031] Figure 2B It is a structural diagram of an eccentric sleeve in the first rotary drive unit of the present invention.

[0032] Figure 2C It is a stress cloud diagram of the eccentric shaft in the first rotation drive unit of the present invention.

[0033] Figure 2D It is an assembly cross-sectional view of the first rotary drive unit and the external gear of the present invention.

[0034] Figure 3 4 is an exploded view of the second rotary drive unit of the present invention.

[0035] Figure 4 It is an exploded view of the third rotation drive unit of the present invention.

[0036] Figure 5 It is a structural diagram of the internal gear of the present invention.

[0037] Figure 5A It is an assembly cross-sectional view of the internal gear, the external gear and the first rotation driving unit of the present invention.

[0038] Figure 6 It is a structural diagram of the frame of the present invention.

[0039] Fig. 6A It is another perspective structural diagram of the frame of the present invention.

[0040] Figure 7 It is a structural diagram of the first gear cover of the present invention.

[0041] Fig. 7A It is a structural diagram of the first gear cover from another perspective of the present invention.

[0042] Figure 8 It is a structural diagram of the first external gear of the present invention.

[0043] Fig. 8A This is a structural diagram of the first external gear from another perspective of the present invention.

[0044] Fig. 9 It is the maximum bending stress of the gear under different torques with different numbers of external gears.

[0045] Fig.10 It is the angular velocity curve of the internal gear when there are two external gears in the distributed KHV type involute small tooth difference joint module of the present invention.

[0046] Fig.11 It is the stress cloud diagram and deformation cloud diagram of the gear under different loads of the distributed KHV type involute small tooth difference joint module of the present invention.

[0047]

[0048] DETAILED DESCRIPTION

[0049] The present invention will be further described in detail below with reference to the accompanying drawings. The various parameter demonstrations listed are only preferred embodiments of the present invention. It should be noted that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention.

[0050] See also Figure 1 , Figure 1A , Figure 1B , Figure 1C , Figure 1D As shown, a distributed KHV type involute small-tooth difference joint module designed by the present invention is applied to a serpentine robotic arm, which includes a first rotation drive unit 1, a second rotation drive unit 2, a third rotation drive unit 3, an internal gear 4, a frame 5, a uniform-section thin-walled bearing 6, a first gear cover 41, a second gear cover 61, a first external gear 7, and a second external gear 8.

[0051] The first rotation driving unit 1 , the second rotation driving unit 2 and the third rotation driving unit 3 have the same structure.

[0052] The first gear cover 41 has the same structure as the second gear cover 61. The first external gear 7 has the same structure as the second external gear 8. The D-axis center hole 41F of the first gear cover 41, the G-axis center hole 7E of the first external gear 7, the H-axis center hole 8E of the second external gear 8 and the F-axis center hole 61F of the second gear cover 61 are aligned and kept coaxial, as shown in FIG. Figure 1C shown.

[0053] The frame 5 and the internal gear 4 remain coaxial, so that the internal gear 4 can only make circular motion around the central axis of the central hole (41F), and the assembly positions of the three rotary drive units (1, 2, 3) are constrained by the frame 5. The two eccentric shaft segments on the eccentric shaft sleeve of each rotary drive unit are coaxial with the three equally divided circular holes of the external gear (7, 8), thereby constraining the movement of the external gear (7, 8).

[0054] In order to reduce the overall volume of the joint module in the serpentine robot arm, the lower end of the inner gear 4 and the frame 5 are matched by a uniform cross-section thin-walled bearing 6 to achieve translation. The preferred size of the uniform cross-section thin-walled bearing 6 is 66.2 mm for the inner ring, 88.9 mm for the outer ring, and 6.35 mm for the thickness. The uniform cross-section thin-walled bearing 6 is a bearing with a special cross-sectional width and thickness; the same cross-sectional size can match many different bearing inner diameters; the width and thickness of the standard bearing increase proportionally with the increase of the bearing inner diameter, while the uniform cross-sectional thin-walled bearing 6 increases the inner diameter and keeps the cross-sectional size unchanged. Therefore, when the bearing diameter is large, the uniform cross-sectional thin-walled bearing 6 can significantly reduce the overall volume of the structure. The inner gear 4, as the output of the joint module, has a threaded hole on its upper end face, which is used to connect the output actuator, and a threaded hole is opened on the lower end face to fix the inner gear bearing cover 42. The design of the inner gear bearing cover 42 is conducive to preventing the uniform cross-sectional thin-walled bearing 6 from falling off.

[0055] The invention designs a distributed KHV type involute small tooth difference joint module, which adopts multiple eccentric shaft inputs (i.e., the eccentric shafts in the rotation drive unit) in the structural optimization design, the outer gear 4 performs translation, and the inner gears (7, 8) rotate as output. The distributed KHV type transmission mode is planetary gear transmission. During the transmission process of the joint module driven by a motor, the eccentric shaft rotates to drive the inner gears (7, 8) to output the speed, and the outer gear 4 translates.

[0056] In order to meet the needs of the snake-like robot arm for the distributed KHV involute small-tooth difference joint module, except for the motor, the remaining parts can be made of steel, aluminum alloy, resin materials, etc. If the processing technology is miniaturized, it can also be formed by 3D printing.

[0057] The first rotary drive unit 1

[0058] See also Figure 2 , Figure 2A The cross-sectional structure and exploded view of the first rotary drive unit 1 are shown, and the first rotary drive unit 1 includes a DC brushless motor A 1A, an eccentric shaft cover 1B, an AA deep groove ball bearing 1C, an AB deep groove ball bearing 1D, an A reverse retaining spring 1E, an eccentric shaft 1F and an A shaft ring 1G.

[0059] like Figure 2A As shown, the center of the A eccentric shaft cover plate 1B is provided with an AA center through hole 1B1, and the AA center through hole 1B1 is surrounded by AA countersunk holes 1B2, AB countersunk holes 1B3, and AC countersunk holes 1B4. The AA center through hole 1B1 is used for the motor output shaft 1A1 of the A DC brushless motor 1A to pass through.

[0060] like Figure 2 , Figure 2AAs shown, the center of the front panel 1F5 of the A eccentric shaft 1F is provided with an AB center through hole 1F1, and the AB center through hole 1F1 is surrounded by AA through holes 1F2, AB through holes 1F3, and AC through holes 1F4. The AB center through hole 1F1 is used for the motor output shaft 1A1 of the A DC brushless motor 1A to pass through. That is, the motor output shaft 1A1 of the A DC brushless motor 1A passes through the AB center through hole 1F1 of the front panel 1F5 and the AA center through hole 1B1 of the A eccentric shaft cover 1B in sequence. The A DC brushless motor 1A is placed in the cavity 1F6 of the A eccentric shaft 1F (as shown in FIG. 1 ). Figure 2B As shown), and by cooperating with the screws and the threaded holes, the A DC brushless motor 1A is fixed on the A eccentric shaft cover 1B.

[0061] like Figure 2 , Figure 2A As shown, the outside of the A eccentric shaft 1F is provided with an AA shaft section 1F7, an AB shaft section 1F8, an AC shaft section 1F9, and a retaining groove 1F10 in sequence. An AA deep groove ball bearing 1C is installed on the AA shaft section 1F7. An AB deep groove ball bearing 1D is installed on the AB shaft section 1F8. An A shaft ring 1G is installed on the AC shaft section 1F9. An A reverse retaining spring 1E is installed on the retaining groove 1F10.

[0062] like Figure 2 As shown, the motor output shaft 1A1 of the motor 1A passes through the AB center through hole 1F1 of the A eccentric shaft 1F and the AA center through hole 1B1 of the A eccentric shaft cover plate 1B in sequence; the A eccentric shaft 1F and the A eccentric shaft cover plate 1B are fixed to the front end cover of the motor 1A by screws; the AA deep groove ball bearing 1C is installed on the AA shaft section 1F7 of the A eccentric shaft 1F, the AB deep groove ball bearing 1D is installed on the AB shaft section 1F8, the A shaft ring 1G is installed on the AC shaft section 1F9, and the A reverse retaining spring 1E is installed on the retaining groove 1F10. The rear end cover of the motor 1A is fixed on the frame 5.

[0063] Second rotary drive unit 2

[0064] See also Figure 3 The exploded structure diagram of the second rotation drive unit 2 shown in the figure, the second rotation drive unit 2 includes a B DC brushless motor 2A, a B eccentric shaft cover plate 2B, a BA deep groove ball bearing 2C, a BB deep groove ball bearing 2D, a B reverse retaining spring 2E, a B eccentric shaft 2F and a B shaft ring 2G.

[0065] A BA center through hole 2B1 is provided at the center of the B eccentric shaft cover plate 2B, and a BA countersunk hole 2B2, a BB countersunk hole 2B3, and a BC countersunk hole 2B4 are provided around the BA center through hole 2B1. The BA center through hole 2B1 is used for the motor output shaft 2A1 of the B DC brushless motor 2A to pass through.

[0066] A BB center through hole 2F1 is provided at the center of the front panel 2F5 of the B eccentric shaft 2F, and a BA through hole 2F2, a BB through hole 2F3, and a BC through hole 2F4 are provided around the BB center through hole 2F1. The BB center through hole 2F1 is used for the motor output shaft 2A1 of the B DC brushless motor 2A to pass through. That is, the motor output shaft 2A1 of the B DC brushless motor 2A passes through the BB center through hole 2F1 of the front panel 2F5 and the BA center through hole 21B1 of the B eccentric shaft cover 2B in sequence. The B DC brushless motor 2A is placed in the cavity of the B eccentric shaft 2F, and the B DC brushless motor 2A is fixed to the B eccentric shaft cover 2B by the cooperation of the screws and the threaded holes.

[0067] The outside of the B eccentric shaft 2F is provided with a BA shaft section 2F7, a BB shaft section 2F8, a BC shaft section 2F9, and a retaining groove 2F10 in sequence. A BA deep groove ball bearing 2C is installed on the BA shaft section 2F7. A BB deep groove ball bearing 2D is installed on the BB shaft section 2F8. A B shaft ring 2G is installed on the BC shaft section 2F9. A B reverse retaining spring 2E is installed on the retaining groove 2F10.

[0068] The third rotary drive unit 3

[0069] See also Figure 4 The exploded structure diagram of the third rotation drive unit 3 shown in the figure, the third rotation drive unit 3 includes a C DC brushless motor 3A, a C eccentric shaft cover plate 3B, a CA deep groove ball bearing 3C, a CB deep groove ball bearing 3D, a C reverse retaining spring 3E, a C eccentric shaft 3F and a C shaft ring 3G.

[0070] A CA center through hole 3B1 is provided at the center of the C eccentric shaft cover plate 3B, and CA countersunk holes 3B2, CB countersunk holes 3B3, and CC countersunk holes 3B4 are provided around the CA center through hole 3B1. The CA center through hole 3B1 is used for the motor output shaft 3A1 of the C DC brushless motor 3A to pass through.

[0071] A CB center through hole 3F1 is provided at the center of the front panel 3F5 of the C eccentric shaft 3F, and CA through holes 3F2, CB through holes 3F3, and CC through holes 3F4 are provided around the CB center through hole 3F1. The CB center through hole 3F1 is used for the motor output shaft 3A1 of the C DC brushless motor 3A to pass through. That is, the motor output shaft 3A1 of the C DC brushless motor 3A passes through the CB center through hole 3F1 of the front panel 3F5 and the CA center through hole 31B1 of the C eccentric shaft cover plate 3B in sequence. The C DC brushless motor 3A is placed in the cavity of the C eccentric shaft 3F, and the C DC brushless motor 3A is fixed to the C eccentric shaft cover plate 3B by the cooperation of the screws and the threaded holes.

[0072] The exterior of the C eccentric shaft 3F is provided with a CA shaft section 3F7, a CB shaft section 3F8, a CC shaft section 3F9, and a retaining groove 3F10 in sequence. A CA deep groove ball bearing 3C is mounted on the CA shaft section 3F7. A CB deep groove ball bearing 3D is mounted on the CB shaft section 3F8. A C shaft ring 3G is mounted on the CC shaft section 3F9. A C reverse retaining spring 3E is mounted on the retaining groove 3F10.

[0073] The three rotation drive units in the distributed KHV type involute small tooth difference joint module designed by the present invention adopt DC brushless motors (1A, 2A, 3A), preferably 2008 model aircraft model small motors, the end of the motor rotor shaft is inlaid with radial magnetized magnetic rings, and the maximum output torque of the motor can be calculated according to the eccentric shaft torque to be 0.085N·m. The motor parameters are shown in Table 1.

[0074] Table 1 Model aircraft motor parameters

[0075] Stator outer diameter 20mm No-load current 0.33A / 10V Stator thickness 8mm Phase resistance 379.3mΩ Number of stator slots 12 Maximum current 8.9A Number of rotor poles 14 Maximum Power 112.14W Speed ​​constant 1000rpm / V Rated voltage 12.6V weight 27.08g Motor size 23.8×18.9mm

[0076] The maximum load of the motors in the three rotary drive units of the distributed KHV involute small-tooth difference joint module designed by the present invention is 6.30 N·m. The maximum load when the three motors are driven simultaneously is 18.9 N·m. The maximum speed of each motor drive is 137.0 rpm.

[0077] In the rotary drive unit with an eccentric shaft system designed by the present invention, the eccentric shaft (1F, 2F, 3F) is the active rotating shaft. In order to make the structure more compact and ensure the torsional strength of the eccentric shaft, the eccentric shaft is designed as a hollow shaft sleeve type, and the motor is placed in the cavity of the eccentric shaft. The end of one side of the eccentric shaft is closed (i.e., the front panel) and has three through holes for connecting with the motor rotor, such as Figure 2A , Figure 3 , Figure 4 shown.

[0078] The present invention uses Abaqus software to perform verification simulation on the eccentric shaft. When the load of the rotary drive unit is 200N, a single motor is used for driving, the input torque of the eccentric shaft is 2.7N·m, and the torque is applied to the cylindrical inner surface of the eccentric shaft. The two deep groove ball bearings are fixed to the bearing section of the cylindrical outer surface of the eccentric shaft. The stress cloud diagram is as follows: Figure 2C As shown, the maximum stress of the eccentric shaft is less than the yield stress, which meets the use requirements.

[0079] The 6706 model deep groove ball bearing is used between the eccentric shaft and the outer gear equally divided hole to reduce the rotation friction. The two bearings on the eccentric shaft are axially positioned by the end cover plus bolts and the shaft ring plus shaft retaining spring. The bolts are also used to fix the motor rotor to the eccentric shaft. The assembly diagram and exploded view of the eccentric shaft system are shown as follows: Figure 2 , Figure 2Ashown.

[0080] In the rotary drive unit with an eccentric shaft system designed in the present invention, the motor drives the eccentric shaft to rotate, and the deep groove ball bearing installed on the eccentric shaft realizes the rotation of the outer gear (7, 8) relative to the inner gear (4), and the frame 5 also rotates relative to the inner gear (4).

[0081] Internal gear 4

[0082] like Figure 1D , Figure 5 , Figure 5A As shown, the inner ring surface of the internal gear 4 is provided with D inner teeth 4A, D inner convex ring 4C and D bearing segment 4B in sequence. The D inner convex ring 4C is used to block and limit the movement of the uniform cross-section thin-walled bearing 6 in the up and down directions, that is, the upper end surface of the outer ring of the uniform cross-section thin-walled bearing 6 is pressed by the lower end surface of the D inner convex ring 4C, and on the other hand, the lower end surface of the outer ring of the uniform cross-section thin-walled bearing 6 is pressed by the upper end surface of the internal gear bearing cover 42, the outer ring of the uniform cross-section thin-walled bearing 6 is connected to the D bearing segment 4B of the internal gear 4, and the inner ring of the uniform cross-section thin-walled bearing 6 is connected to the E bearing segment 5F of the frame 5, as shown in FIG. Figure 5A shown.

[0083] The D internal teeth 4A of the internal gear 4 are used to mesh with the G external teeth 7D on the first external gear 7 and the H external teeth 8D on the second external gear 8 (such as Figure 1B , Figure 1C , Figure 5A The D bearing section 4B of the internal gear 4 is sleeved with a uniform cross-section thin-walled bearing 6 (as shown in FIG. Figure 1B , Figure 1C , Figure 5A As shown), the outer ring of the uniform cross-section thin-walled bearing 6 is connected to the bearing segment 4B of the internal gear 4, and the inner ring of the uniform cross-section thin-walled bearing 6 is connected to the E bearing segment 5F of the frame 5, which is conducive to the movement of the distributed KHV type middle mechanism relative to the internal gear 4.

[0084] Rack 5

[0085] See also Figure 1A , Figure 1B , Figure 1C , Figure 1D , Figure 5A , Figure 6 , Fig. 6AAs shown, the bottom panel 5D of the frame 5 is provided with an EA through hole 5D1, an EB through hole 5D2, an EC through hole 5D3 and an E wiring hole 5E for wiring (at least for the three-phase wires of the motor to pass through). One end of the bottom panel 5D of the frame 5 is provided with an EA inner boss 5A, an EB inner boss 5B, and an EC inner boss 5C; the other end of the bottom panel 5D is provided with an EA base 5A1 at a position corresponding to the EA inner boss 5A, an EB base 5B1 at a position corresponding to the EB inner boss 5B, and an EC base 5C1 at a position corresponding to the EC inner boss 5C. An E bearing segment 5F and an E outer ring 5G are provided on the outer cylindrical surface of the frame 5, and the inner ring of a uniform cross-section thin-walled bearing 6 is connected to the E bearing segment 5F. The upper end face of the inner ring of the uniform cross-section thin-walled bearing 6 is pressed by the bearing inner ring baffle 62, and the lower end face of the inner ring of the uniform cross-section thin-walled bearing 6 is pressed by the upper end face of the E outer ring 5G of the frame 5, as shown in FIG. Figure 5A shown.

[0086] exist Figure 1D In the embodiment, the three inner bosses (5A, 5B, 5C) on the frame 5 are aligned with the three inner bosses (62A, 62B, 62C) on the bearing inner ring baffle 62 and fixed by screws, so that the bearing inner ring baffle 62 is fixed on the frame 5, as shown in FIG. Figure 5A shown.

[0087] The motor stator of the A DC brushless motor 1A in the first rotation drive unit 1 is mounted at the EA through hole 5D1.

[0088] The motor stator of the B DC brushless motor 2A in the second rotation drive unit 2 is mounted at the EB through hole 5D2.

[0089] The motor stator of the C DC brushless motor 3A in the third rotation drive unit 3 is mounted at the EC through hole 5D3 .

[0090] In the present invention, the E bearing segment 5F on the outer cylindrical surface of the frame 5 is used for axial fixation of the inner ring of the uniform cross-section thin-walled bearing 6. The E bearing segment 5F on the outer cylindrical surface of the frame 5 and the E outer ring 5G form a stepped shaft, which also takes into account the design requirements of miniaturization of the frame 5 structure.

[0091] In the present invention, a structural design of three bases (EA base 5A1, EB base 5B1, EC base 5C1) is designed at the bottom of the frame 5. On the one hand, this can reduce the vibration of the rotation drive unit (1, 2, 3) during operation, and on the other hand, it is also convenient for fixing the distributed KHV type involute small tooth difference joint module of the present invention to the platform in the application scenario.

[0092] First gear cover 41

[0093] In the present invention, the first gear cover 41 and the second gear cover 61 have the same structure, but are assembled relative to each other. Figure 1B , Figure 1C , Figure 2D , Figure 5A shown.

[0094] like Figure 7 , Fig. 7A As shown, a D center hole 41F is provided at the center of the first gear cover 41, and then a DA through hole 41A, a DB through hole 41B, and a DC through hole 41C are provided in three equal parts.

[0095] The DA through hole 41A is used to place the first rotation drive unit 1. The DB through hole 41B is used to place the second rotation drive unit 2. The DC through hole 41C is used to place the third rotation drive unit 3.

[0096] The DB panel 41E of the first gear cover 41 is provided with a DA convex ring 41A1, a DB convex ring 41B1, and a DC convex ring 41C1, and the DA convex ring 41A1 is located at the DA through hole 41A, the DB convex ring 41B1 is located at the DB through hole 41B, and the DC convex ring 41C1 is located at the DC through hole 41C. The convex rings at the through holes are used to press the outer ring of the bearing.

[0097] The DA panel 41D of the first gear cover 41 is provided with a D-counter countersunk through hole 41D1 for a screw to pass through.

[0098] The DA outer convex ring 41A1 is used to press the upper end surface of the outer ring of the AA deep groove ball bearing 1C in the first rotation drive unit 1.

[0099] The DB outer convex ring 41B1 is used to press the upper end surface of the outer ring of the BA deep groove ball bearing 2C in the second rotation drive unit 2.

[0100] The DC outer convex ring 41C1 is used to press the upper end surface of the outer ring of the CA deep groove ball bearing 3C in the third rotation drive unit 3.

[0101] Second gear cover 61

[0102] The second gear cover 61 is provided with an F center hole 61F at its center, and then divided into three equal parts: an FA through hole 61A, an FB through hole 61B, and an FC through hole 61C.

[0103] The FA through hole 61A is used to place the first rotation drive unit 1. The FB through hole 61B is used to place the second rotation drive unit 2. The FC through hole 61C is used to place the third rotation drive unit 3.

[0104] The FB panel 61E of the second gear cover 61 is provided with FA convex ring, FB convex ring and FC convex ring, and the FA convex ring is located at the FA through hole 61A, the FB convex ring is located at the FB through hole 61B, and the FC convex ring is located at the FC through hole 61C. The convex rings at the through holes are used to support the outer ring of the bearing.

[0105] The FA outer convex ring is used to press against the upper end surface of the outer ring of the AB deep groove ball bearing 1D in the first rotation drive unit 1 .

[0106] The FB outer convex ring is used to press against the upper end surface of the outer ring of the BB deep groove ball bearing 2D in the second rotation drive unit 2.

[0107] The FC outer convex ring is used to press against the upper end surface of the outer ring of the CB deep groove ball bearing 3D in the third rotation drive unit 3.

[0108] The cooperation between the first gear cover 41 and the first external gear 7 can restrict the movement of the outer ring of the AA deep groove ball bearing 1C in the up-down direction.

[0109] The cooperation between the second gear cover 61 and the second external gear 8 can restrict the movement of the outer ring of the AB deep groove ball bearing 1D in the up-down direction.

[0110] Bearing inner ring baffle 62

[0111] like Figure 1D , Figure 5A As shown, the bearing inner ring baffle 62 is provided with an FA inner boss 62A, an FB inner boss 62B, and an FC inner boss 62C.

[0112] The EA inner boss 5A on the frame 5 is aligned with the FA inner boss 62A on the bearing inner ring baffle 62 and then fixed by screws.

[0113] The EB inner boss 5B on the frame 5 is aligned with the FB inner boss 62B on the bearing inner ring baffle 62 and then fixed by screws.

[0114] The EC inner boss 5C on the frame 5 is aligned with the FC inner boss 62C on the bearing inner ring baffle 62 and then fixed by screws.

[0115] First external gear 7

[0116] In the present invention, the first external gear 7 and the second external gear 8 have the same structure, but are assembled relative to each other. Figure 1B , Figure 1C , Figure 2D , Figure 5A shown.

[0117] like Figure 8 , Fig. 8AAs shown, a G center hole 7E is provided at the center of the first external gear 7, and then a GA stepped through hole 7A, a GB stepped through hole 7B, and a GC stepped through hole 7C are provided in three equal parts.

[0118] A GA inner baffle plate 7A1 is provided in the GA stepped through hole 7A. The GA inner baffle plate 7A1 is used to press against the lower end surface of the outer ring of the AA deep groove ball bearing 1C in the first rotary drive unit 1.

[0119] A GB inner baffle plate 7B1 is provided in the GB stepped through hole 7B. The GB inner baffle plate 7B1 is used to press against the lower end surface of the outer ring of the AA deep groove ball bearing 2C in the second rotation drive unit 2.

[0120] A GC inner baffle plate 7C1 is provided in the GC stepped through hole 7C. The GC inner baffle plate 7C1 is used to press against the lower end surface of the outer ring of the AA deep groove ball bearing 3C in the third rotation drive unit 3.

[0121] G external teeth 7D are provided on the outer circumferential surface of the first external gear 7 , and the G external teeth 7D mesh with the D internal teeth 4A of the internal gear 4 .

[0122] The GA face plate 71 of the first external gear 7 has a GA stepped through hole 7A, a GB stepped through hole 7B, and a GC stepped through hole 7C.

[0123] The GB face plate 72 of the first external gear 7 is a smooth surface.

[0124] Second external gear 8

[0125] The second external gear 8 has an H center hole 8E at its center, and is then divided into three equal parts: an HA stepped through hole 8A, an HB stepped through hole 8B, and an HC stepped through hole 8C.

[0126] An HA inner baffle is provided in the HA stepped through hole 8A and is used to press against the lower end surface of the outer ring of the AA deep groove ball bearing 1C in the first rotary drive unit 1 .

[0127] An HB inner baffle is provided in the HB stepped through hole 8B and is used to press against the lower end surface of the outer ring of the AA deep groove ball bearing 2C in the second rotary drive unit 2 .

[0128] An HC inner baffle is provided in the HC stepped through hole 8C and is used to press against the lower end surface of the outer ring of the AA deep groove ball bearing 3C in the third rotation drive unit 3 .

[0129] H external teeth 8D are provided on the outer circumferential surface of the second external gear 8 , and the H external teeth 8D mesh with the D internal teeth 4A of the internal gear 4 .

[0130] The HA panel of the second external gear 8 has HA stepped through holes 8A, HB stepped through holes 8B, and HC stepped through holes 8C.

[0131] The HB face plate 82 of the second external gear 8 is a smooth surface.

[0132] In the present invention, the equally divided holes of the external gears (7, 8) are stepped holes for axial positioning on one side of the bearing, and the axial positioning on the other side of the bearing is through a retaining ring. The three retaining rings are a whole and are fixed to the external gear through threaded connection.

[0133] In the present invention, the first gear cover 41, the first external gear 7, the second external gear 8 and the second gear cover 61 are all provided with through holes in three equal parts, and baffles are also provided in the through holes to form a stepped hole structure such as Figure 1D As shown. This stepped equally divided through hole cooperates with the bearing and is used for axial positioning on one side of the bearing. The axial positioning on the other side of the bearing is through a retaining ring. The three retaining rings are a whole and are fixed to the external gears (7, 8) by threaded connection. On the other hand, after the DA through hole 41A of the first gear cover 41, the GA stepped through hole 7A of the first external gear 7, the HA stepped through hole 8A of the second external gear 8 and the FA through hole 61A of the second gear cover 61 are aligned, they are used to place the first rotation drive unit 1; after the DB through hole 41B of the first gear cover 41, the GB stepped through hole 7B of the first external gear 7, the HB stepped through hole 8B of the second external gear 8 and the FB through hole 61B of the second gear cover 61 are aligned, they are used to place the second rotation drive unit 2; after the DC through hole 41C of the first gear cover 41, the GC stepped through hole 7C of the first external gear 7, the HC stepped through hole 8C of the second external gear 8 and the FC through hole 61C of the second gear cover 61 are aligned, they are used to place the third rotation drive unit 3

[0134] Example 1

[0135] In order to more intuitively understand the motion process of the involute small-tooth difference transmission applied on the serpentine robot arm, the feasibility and rationality of the motion principle, mechanical structure, and control system of the distributed KHV type rotary drive unit designed in this study are further tested. The overall structural dimensions of the distributed KHV type rotary drive unit designed by the present invention are 115mm in diameter, 26mm in thickness, 1.05 in gear transmission overlap, and 0.053 in tooth profile overlap, and performance tests are carried out.

[0136] The three motors in the prototype are DJ Yu 2008 brushless motors, and the specific parameters of the motors are shown in Table 1. All non-standard parts in the prototype, such as gears, racks, eccentric shafts, retaining rings, etc., are made of 3D resin materials with a processing accuracy of ±200μm.

[0137] When the output of the serpentine robot drive unit is rotational motion, harmonic, planetary and other reducers are often used to increase the torque. In-depth research has found that the involute small-tooth difference gear transmission is more suitable for the drive unit of the serpentine robot due to its large transmission ratio, compact structure, reliable operation, and high overload and impact resistance. The transmission effect of the rotary drive unit was tested. The main purpose of the test was to verify the stability of the operation of the rotary drive unit, so as to illustrate the feasibility of the mechanism principle and control system. The experimental content is to measure the output speed of the internal gear of the rotary drive unit at different input speeds, and calculate the actual transmission ratio of the rotary drive unit prototype based on the experimental results. Two groups of experiments were conducted in total. One group only powered one motor and controlled the motor to move at a uniform speed at different speeds; the other group powered three motors at the same time, with the same speed of the three motors, and controlled the motor to move at a uniform speed at different speeds.

[0138] The angular velocity of the internal gear is measured using a handheld tachometer, the tachometer model is Shengli VC6235P. The experimental measured data are shown in Table 2. It can be seen from the table that when the motor input speed is 400rpm~2000rpm, the transmission ratio of the linear drive unit of the two groups of experiments is relatively stable, and the error with the theoretical value of 92 is within 3%, which shows the feasibility of the transmission principle and control system of the linear drive unit.

[0139] Table 2 Experimental results of the rotary drive unit prototype

[0140]

[0141] In the present invention, the maximum bending stress of the gear when the double external gears (7, 8) are used under different loading torques is obtained by finite element simulation, and compared with the conventional single external gear, see Table 3 and Fig. 9 . Considering that in the KHV type small tooth difference transmission, the external gear performs high-speed eccentric motion, and there is an eccentric weight in the joint module, periodic interference force will be generated during operation, thereby generating vibration, aggravating bearing wear, and reducing bearing service life. In severe cases, accidents may even occur. Therefore, balancing measures must be taken to eliminate or reduce vibration. Because the ratio of the tooth thickness of the external gear used in the present invention to the gear diameter is small, the eccentric mass can be regarded as distributed in a rotating plane, so only static balance can be performed. Two identical external gears can be installed symmetrically relative to the center axis of the internal gear. During movement, the eccentricity is equal in size and opposite in direction, and offsets each other.

[0142] Table 3 Maximum bending stress of gears under different torques with different numbers of external gears

[0143]

[0144] exist Fig. 9Taking the safety factor as 1.25, the allowable bending stress is 400 MPa, and the maximum output torque of the distributed KHV type rotary drive unit using the double external gear design of the present invention is 200 N·m.

[0145] In order to verify whether the transmission principle of the three sets of rotating drive units (1, 2, 3) designed by the present invention is feasible, the working state is determined, and the force condition of the eccentric shaft (1C, 2C, 3C) is obtained (providing parameter constraints for the structural design of the eccentric shaft), and a dynamic simulation analysis is performed on it. Since the three sets of rotating drive units (1, 2, 3) and the external gear (7, 8), the external gear (7, 8) and the internal gear 4 adopt a bearing movable connection mode, and the frame 5 and the internal gear 4 are coaxial, so that the internal gear 4 can only make a circular motion around its axis, the position of the three sets of rotating drive units (1, 2, 3) is constrained by the frame 5, and at the same time, the two eccentric shaft sections of the eccentric shaft (1C, 2C, 3C) are coaxial with the three equally divided circular holes of the external gear (7, 8), constraining the movement of the external gear (7, 8). A rotating motor with a constant speed of 100rpm is applied to the eccentric shaft, and the running time is 5s. The output angular velocity fluctuation of the distributed KHV type involute small tooth difference joint module of the present invention is stable, and can even be regarded as completely eliminated. The angular velocity obtained by simulation is 6.52 rad / s. When the eccentric shaft speed is 100 rpm, the angular velocity of the internal gear 4 is 6.52 rad / s. When the rotary motor is applied to two or three eccentric shafts at the same time, the angular velocity output curve is Fig.10 Be consistent.

[0146] In order to determine the number of gear pairs that are in contact with the outer gear (7, 8) and the inner gear 4 when the distributed KHV gear transmission is in meshing, and to verify the calculation results of the transmitted torque with the eccentric shaft (1C, 2C, 3C), a finite element simulation analysis of the distributed KHV gear meshing is performed to obtain the stress cloud diagram and deformation cloud diagram of the gear under different loads, as shown in FIG. Fig.11 As shown. (a) and (b) are stress and deformation cloud diagrams of the gear when the load is 50N·m; (c) and (d) are stress and deformation cloud diagrams of the gear when the load is 150N·m; (e) and (f) are stress and deformation cloud diagrams of the gear when the load is 250N·m. According to the relationship between the maximum bending stress of the gear and the loading torque, since the change in the number of gear pairs in contact at the same time is nonlinear, the slope of the curve decreases with the increase of the loading torque, and is equal when the loading torque is about 220N·m, at which time the maximum bending stress of the gear is 575MPa.

[0147] The distributed KHV type rotary drive unit structure designed by the present invention has motors distributed on gears, which has a compact structure, small size, and flat appearance. Compared with the MIT configuration drive unit of the same specification, the thickness is reduced by 30%; compared with the KHV type transmission, the sliding friction is eliminated and the efficiency is improved; the redundancy is high, and when three motors are driven, only one motor needs to be normal, and the system can work normally under low torque state.

Claims

1. A distributed K-H-V type involute small tooth difference joint module, characterized in that: The joint module is applied to the snake-like robotic arm; The joint module comprises a first rotation drive unit (1), a second rotation drive unit (2), a third rotation drive unit (3), an internal gear (4), a frame (5), a uniform cross-section thin-walled bearing (6), a first gear cover (41), a second gear cover (61), a first external gear (7), and a second external gear (8); Wherein, the first rotation drive unit (1), the second rotation drive unit (2) and the third rotation drive unit (3) have the same structure; Wherein, the first gear cover (41) and the second gear cover (61) have the same structure; The first external gear (7) and the second external gear (8) have the same structure; the GA panel (71) of the first external gear (7) is provided with a stepped through hole for placing a bearing, and the GB panel (72) of the first external gear (7) is a smooth surface; The D-axis center hole (41F) of the first gear cover (41), the G-axis center hole (7E) of the first external gear (7), the H-axis center hole (8E) of the second external gear (8) and the F-axis center hole (61F) of the second gear cover (61) are aligned and kept coaxial; Wherein, the frame (5) and the internal gear (4) are kept coaxial; The first rotary drive unit (1) comprises a DC brushless motor (1A), an eccentric shaft cover plate (1B), an AA deep groove ball bearing (1C), an AB deep groove ball bearing (1D), an A reverse retaining spring (1E), an eccentric shaft (1F) and an A shaft ring (1G); the motor output shaft (1A1) of the motor (1A) passes through the AB center through hole (1F1) of the eccentric shaft (1F) and the AA center through hole (1B1) of the eccentric shaft cover plate (1B) in sequence; the eccentric shaft (1F) and the eccentric shaft cover plate (1B) are fixed to the front end cover of the motor (1A) by screws; the AA deep groove ball bearing (1C) is installed on the AA shaft section (1F7) of the eccentric shaft (1F), the AB deep groove ball bearing (1D) is installed on the AB shaft section (1F8), the A shaft ring (1G) is installed on the AC shaft section (1F9), and the retaining groove (1F 10) A reverse retaining spring (1E) is installed on it; The inner ring surface of the internal gear (4) is provided with D inner teeth (4A), D inner convex ring (4C) and D bearing section (4B) in sequence; the D inner convex ring (4C) is used to block and limit the movement of the uniform cross-section thin-walled bearing (6) in the up and down directions; the outer ring of the uniform cross-section thin-walled bearing (6) is connected to the D bearing section (4B) of the internal gear (4); the inner ring of the uniform cross-section thin-walled bearing (6) is connected to the E bearing section (5F) of the frame (5); the D inner teeth (4A) of the internal gear (4) are used to mesh with the G outer teeth (7D) on the first outer gear (7) and the H outer teeth (8D) on the second outer gear (8); The joint module uses two external gears (7, 8) of the same structure and are placed symmetrically relative to the central axis of the internal gear (4). When moving, the eccentricity is equal in size and opposite in direction, and they cancel each other out.

2. The distributed K-H-V type involute small tooth difference joint module according to claim 1 is characterized in that: During the transmission process of the joint module driven by the motor, the eccentric shaft rotates to drive the internal gear to output the speed, and the external gear moves horizontally.

3. The distributed K-H-V type involute small tooth difference joint module according to claim 1 is characterized in that: The joint module has a flat structure.

4. The distributed K-H-V type involute small tooth difference joint module according to claim 1 is characterized in that: The joint module adopts a distributed K-H-V type rotary drive unit with double external gear design, with a maximum output torque of 200N·m 。 5. The distributed K-H-V type involute small tooth difference joint module according to claim 1 is characterized in that: The joint module is made of steel, aluminum alloy or resin.

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