A planetary gear reducer for robots

Abstract

The present invention discloses a planetary gear reducer for robots, which solves the problem that the existing planetary gear reducer has a large axial dimension, which leads to an increase in the span of the planetary shaft and a weakened rigidity. The reducer adopts a hole retaining ring to axially position the planetary gear of the first-stage planetary gear reduction mechanism, the current-stage planetary frame to axially position the planetary gear bearing, and the upper-stage planetary frame is axially positioned by the first external tooth of the next-stage sun gear. At the same time, the same-stage planetary gear and the planetary frame are in direct contact to achieve mutual axial positioning. Compared with the existing reducer structure, the structure of the present invention not only shortens the overall axial dimension of the planetary gear reducer, but also reduces the characteristics and quantity of parts, thereby reducing the manufacturing cost.

Description

Technical Field

[0001] The invention relates to a gear transmission device, in particular to a planetary gear reducer for a robot. Background Art

[0002] Existing robot reducers usually adopt RV reducer structure. The advantages of RV reducer are small size and large reduction ratio, but relatively speaking, due to the cycloid gear structure, it is difficult to process, high cost, low transmission efficiency, and poor precision retention. Planetary gear reducer is superior to RV reducer in terms of cost, efficiency, and precision retention.

[0003] For example: Chinese patent, application number: CN200710068194.9 discloses a "closed planetary gear reducer", such as Figure 1 As shown, the reducer is a three-stage planetary gear structure, wherein the input end high-speed sun gear 14 contacts the housing (actually the end cover 18) through the bearing 19 for axial positioning, and the output end low-speed planetary shaft 5 contacts the output flange (i.e., the three-stage planetary carrier 34) for axial positioning. The sun gears of each stage are contacted and positioned with each other; the planetary carriers of each stage are axially positioned by the retaining springs on the sun gears and the end faces of the sun gear teeth; the planetary gear shafts are axially fixed to the planetary carriers through the shaft shoulders and retaining springs; the planetary gears are positioned on the planetary shafts through the bearings of the planetary shafts on one side and on the planetary carriers on the other side.

[0004] However, the planetary gear reducer with the above structure has the following problems:

[0005] 1. A large number of retaining springs are used for axial positioning, which not only occupies the axial size, but also increases the span of the planetary shaft itself and weakens the rigidity. At the same time, due to the large axial size, it will not be able to meet some scenarios with more stringent requirements on the use space.

[0006] 2. The planetary gear reducer uses deep groove ball bearings between the low-speed planet carrier and the inner gear housing as the output end. However, since deep groove ball bearings are mainly used to bear radial loads, their bearing capacity for axial loads is weak, which reduces the reducer's bearing capacity for axial and moment loads. In some structures, deep groove ball bearings are replaced with double-row angular contact ball bearings, but the use of such bearings will make the entire reducer occupy too much space and also reduce the power density of the reducer.

[0007] 3. The planetary wheel bearings between the planetary wheels and the planetary shafts in the planetary gear reduction mechanisms at all levels mostly use needle roller bearings. After assembly, the needle roller bearings are in line contact with the inner hole of the planetary wheel and the outer circle of the planetary shaft.

[0008] However, due to manufacturing errors (cylindricity errors of the three parts, the needle roller, the inner hole of the planetary gear, and the outer circle of the planetary shaft), there will actually be a point contact close to one end of the needle roller's axis, causing the radial load on the needle roller to be unevenly distributed along the axial direction, which in turn causes the friction force of the needle roller along the axial direction to be uneven, making the needle roller's own axis not perpendicular to the direction of movement. This inclination will increase the frictional resistance and produce drag, causing the needle roller to fail quickly.

[0009] In addition, when the reducer is loaded, the planetary carrier as the low-speed output end needs to bear a torsional load that is much greater than the torsional load at the other end (input end) when resisting the output torque, causing the planetary carrier used as the low-speed output end to undergo torsional deformation, resulting in bending deformation of the planetary shaft, which further destroys the linear contact of the needle roller bearing.

[0010] The above two factors greatly reduce the transmission efficiency of the needle roller bearing, causing it to fail easily and shortening its service life. It is the link in the reducer that is most prone to failure and damage. Summary of the invention

[0011] In order to solve the problem that the existing planetary gear reducer has a large axial dimension, resulting in an increase in the span of the planetary shaft and a weakened rigidity, as well as the problem that deep groove ball bearings or double-row angular contact ball bearings are used between the planetary carrier at the output end and the inner gear housing, and the problem that the planetary wheel bearings are very easy to fail when needle roller bearings are used, the present invention provides a planetary gear reducer for a robot.

[0012] The specific technical solution of the present invention is:

[0013] A planetary gear reducer for a robot, comprising an inner gear housing and N-stage planetary gear reduction mechanisms arranged in sequence along the axial direction of the inner gear housing; N≥2; each stage of the planetary gear reduction mechanism comprises a sun gear, a planetary gear, a planet carrier and a planetary shaft;

[0014] The improvements are:

[0015] The planetary gear of the first-stage planetary gear reduction mechanism is axially positioned by a retaining ring through a hole clamped inside the internal gear housing;

[0016] In the 2nd to Nth stage planetary gear reduction mechanisms, the sun gear is provided with a first external tooth and a second external tooth, and the tooth height of the first external tooth is greater than the tooth height of the second external tooth; the first external tooth is meshed with the planetary gear of the current stage, and the second external tooth is key-connected with the planetary carrier of the previous stage; the end face of the planetary carrier of the previous stage contacts the end face of the first external tooth on the sun gear of the current stage, and at the same time forms a micro gap with the end face of the planetary gear of the current stage;

[0017] The planet shaft of each stage of the planetary gear reduction mechanism is interference fit with the planet shaft mounting hole on the planet carrier, and the planetary gear and the planet carrier of the Nth stage of the planetary gear reduction mechanism are in contact with each other to achieve the axial positioning of the planetary gear in the Nth stage of the planetary gear reduction mechanism;

[0018] In the 1st to Nth stage planetary gear reduction mechanism, the outer surface of the planetary shaft located in the planetary wheel bearing mounting hole is provided with S first inner ring outer raceways arranged side by side in the axial direction, S≥2, and a plurality of first steel balls are arranged along the circumferential direction between each first inner ring outer raceway and the hole wall of the planetary wheel bearing mounting hole; the first steel balls installed in each two adjacent first inner ring outer raceways are arranged in a staggered manner in the circumferential direction, thereby forming the planetary wheel bearing of the Nth stage planetary gear reduction mechanism; a circular arc groove protruding inward is provided on the side of the planetary wheel bearing mounting hole close to the planet carrier, which is used to axially position the first steel balls;

[0019] The planet carrier of the Nth-stage planetary gear reduction mechanism is rotationally connected to the inner gear housing via at least one row of contact ball bearing structures, and the contact ball bearing structure realizes axial positioning of the planet carrier in the Nth-stage planetary gear reduction mechanism;

[0020] The contact ball bearing structure includes M second inner ring outer raceways arranged along the axial direction on the outer surface of the planet carrier of the N-th stage planetary gear reduction mechanism, and M second outer ring inner raceways corresponding to the M second inner ring outer raceways are arranged on the inner wall of the inner gear housing along the axial direction; M≥1;

[0021] M steel ball installation raceways are formed between the M second inner ring outer raceways and the M second outer ring inner raceways; a plurality of second steel balls are arranged in the circumferential direction in each steel ball installation raceway;

[0022] The planet carrier of the Nth-stage planetary gear reduction mechanism is provided with at least one axial hole, and M ball loading holes are provided at positions corresponding to the axial hole and the outer raceway of the second inner ring, and each ball loading hole is provided with an anti-escape structure to prevent the ball from escaping;

[0023] A keyway for connecting with an output end of an external motor is arranged in the central through hole of the sun wheel of the first-stage planetary gear reduction mechanism.

[0024] Furthermore, each of the above-mentioned sun gears has a central through hole; a positioning through hole for installing the motor is set in the center of the planetary carrier of the Nth stage planetary gear reduction mechanism, and a keyway is set in the central through hole of the sun gear in the 1st stage planetary reduction gear mechanism.

[0025] Furthermore, a limiting hole is also provided on the planet carrier of the above-mentioned Nth-stage planetary gear reduction mechanism, and the limiting hole is connected to the ball loading hole; a limiting device is provided in the limiting hole to prevent the anti-escape structure from moving.

[0026] Furthermore, the above-mentioned limiting hole is a screw hole parallel to the axial hole, and the limiting device is a tightening screw.

[0027] Furthermore, when the above M is 1: the steel ball mounting raceway includes four eccentric arcs, each of which occupies 1 / 4 of the circumference of the cross-section, and the second steel ball is in point contact with the four arcs of the steel ball mounting raceway.

[0028] Furthermore, when the above M is 2,

[0029] The first ball installation raceway consists of four eccentric arcs, each of which occupies 1 / 4 of the cross-section circumference;

[0030] The second ball installation raceway consists of four eccentric arcs, each of which occupies 1 / 4 of the circumference of the cross section;

[0031] The arc of the first steel ball mounting raceway is the same as the arc of the second steel ball mounting raceway, and the second steel ball is in point contact with the four arcs of the first steel ball mounting raceway, as well as the second steel ball and the four arcs of the second steel ball mounting raceway.

[0032] Furthermore, when the above M is 2,

[0033] The first ball installation raceway consists of two eccentric arcs, each of which occupies 1 / 2 of the cross-section circumference;

[0034] The second ball installation raceway consists of two eccentric arcs, each of which occupies 1 / 2 of the circumference of the cross section;

[0035] The arc of the first steel ball mounting raceway and the arc of the second steel ball mounting raceway are mirror images.

[0036] Furthermore, when the above M is 3,

[0037] The first ball installation raceway consists of two eccentric arcs, each of which occupies 1 / 2 of the cross-section circumference;

[0038] The second steel ball installation raceway includes four eccentric arcs, each of which occupies 1 / 4 of the circumference of the cross section. The second steel ball is in point contact with the four arcs of the second steel ball installation raceway.

[0039] The third ball installation raceway consists of two eccentric arcs, each of which occupies 1 / 2 of the circumference of the cross section;

[0040] The arc of the first steel ball installation raceway and the arc of the third steel ball installation raceway are mirror images.

[0041] Furthermore, S shallow grooves are arranged on the inner wall of the planetary wheel bearing mounting hole of each stage of the above-mentioned planetary gear reduction mechanism, and the S shallow grooves correspond one-to-one to the S first inner ring outer raceways; the first inner ring outer raceway is composed of a first circular arc and a second circular arc arranged eccentrically, and the first steel ball is respectively in point contact with the first circular arc and the second circular arc, and is in contact with the shallow grooves, thereby forming a three-point contact ball bearing structure.

[0042] Furthermore, the above-mentioned N-stage planetary gear reduction mechanisms share an internal gear housing, and the modules of the planetary gears in each stage of the planetary gear reduction mechanism are the same.

[0043] The present invention has the following beneficial effects:

[0044] 1. The reducer of the present invention adopts a hole retaining ring to axially position the planetary gear of the first-stage planetary gear reduction mechanism, the current-stage planetary carrier axially positions the planetary gear bearing, and the upper-stage planetary carrier axially positions the first external tooth of the next-stage sun gear. At the same time, the same-stage planetary gear and the planetary carrier directly contact each other to achieve mutual axial positioning. Compared with the existing reducer structure, the structure of the present invention not only shortens the overall axial size of the planetary gear reducer, but also reduces the characteristics and number of parts, and reduces the manufacturing cost. At the same time, the center of the planetary carrier of the Nth-stage planetary gear reduction mechanism is provided with a motor positioning through hole for installing, each stage of the sun gear has a central through hole, and the central through hole of the sun gear of the first-stage planetary gear reduction mechanism is provided with a keyway for connecting to the output end of the external motor. This design allows the motor matched with the reducer to be set on the high-speed side (power input side) or on the low-speed side (power output side), so that the entire reducer structure has strong adaptability and can be applied to different usage scenarios.

[0045] 2. In the adjacent two-stage planetary gear reduction mechanism of the present invention, the end face of the upper-stage planet carrier forms a micro gap with the end face of the current-stage planet wheel, which can assume the axial positioning function while leaving space for grease, so that an oil film is established between the contact surfaces, thereby improving lubrication and reducing wear; at the same time, it also increases the manufacturing tolerance and reduces the manufacturing difficulty.

[0046] 3. The planetary wheel bearings in the Nth-stage planetary gear reduction mechanism of the present invention adopt a three-point contact ball bearing structure, which has higher manufacturing precision, stronger load-bearing capacity, stiffness and higher transmission accuracy than the cylindrical needle bearings used in the existing planetary wheel bearings; at the same time, the three-point contact ball bearing structure can be preloaded to eliminate bearing clearance, thereby reducing the reverse clearance of the reducer, and in order to shorten the axial dimension of the planetary gear reduction mechanism, the number of steel ball rows can be increased in the same axial space to improve the load-bearing capacity.

[0047] 4. The planet carrier and the inner gear housing of the Nth-stage planetary gear reduction mechanism of the reducer of the present invention are rotationally connected by arranging a single-row contact ball bearing. This bearing type can not only bear radial loads, but also axial loads. Compared with the structure of the existing reducer, the reducer's bearing capacity for axial and bending loads is greatly improved; at the same time, the contact ball bearing structure adopts a filling structure composed of an axial hole, a ball filling hole and an anti-escape structure, thereby avoiding the problem of splicing gaps that are inevitably generated by adopting an upper and lower splicing structure, thereby improving manufacturing accuracy, thus effectively ensuring the raceway stiffness and reducing the wear of the balls in the raceway caused by the splicing raceway gap.

[0048] 5. The present invention adopts a common inner gear housing for each stage of the planetary gear reduction mechanism, and the same module design is adopted for each stage of the planetary gear, so that the width dimension of the planetary gear in each stage of the planetary mechanism can be thinned, further reducing the axial dimension of the reducer. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a structural schematic diagram of an existing planetary gear reducer.

[0050] Figure 2 This is a schematic structural diagram of the planetary gear reducer for robots of the present invention.

[0051] Figure 3 Schematic diagram of a planetary gear bearing without shallow grooves.

[0052] Figure 4 Schematic diagram of a planetary gear bearing with shallow grooves.

[0053] Figure 5 The figure is a schematic diagram of the circumferentially staggered arrangement of the first steel balls in two adjacent rows in the planetary gear bearing.

[0054] Figure 6 This is a schematic diagram of the end face of the planet carrier of the third-stage planetary gear reduction mechanism.

[0055] Figure 7 It is a partial schematic diagram of the structure of the contact ball bearing installed on the planet carrier;

[0056] Figure 8 It is a schematic diagram of the structure of a single-row contact ball bearing;

[0057] Fig. 9 It is a schematic diagram of the first form of the two-row contact ball bearing structure;

[0058] Fig.10 It is a schematic diagram of the second form of the two-row contact ball bearing structure;

[0059] Fig.11 It is a schematic diagram of the third form of the two-row contact ball bearing structure;

[0060] Fig.12 It is a schematic diagram of a three-row contact ball bearing structure;

[0061] Fig.13 This is a schematic diagram when the motor is set on the power input side;

[0062] Fig.14 This is a schematic diagram when the motor is set on the power output side.

[0063] The reference numerals are as follows:

[0064] 100-inner gear housing, 1001-inner raceway of the second outer ring;

[0065] 200-planetary gear reduction mechanism, 201-sun gear, 2011-first outer tooth, 2012-second outer tooth, 2013-center through hole, 202-planetary gear, 203-planet carrier, 2031-second inner ring outer raceway, 2032-axial hole, 2033-ball filling hole, 2034-motor positioning through hole, 204-planetary shaft, 2041-first inner ring outer raceway, 2042-arc-shaped channel, 206-planetary shaft mounting hole, 207-planetary gear inner hole, 2071-shallow groove;

[0066] 300- retaining ring for hole;

[0067] 400-first steel ball;

[0068] 500-Steel ball installation raceway;

[0069] 600-second steel ball;

[0070] 700-anti-slip structure, 701-pin shaft, 702-limiting hole, 703-tightening screw. DETAILED DESCRIPTION

[0071] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0072] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0073] At the same time, in the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper, lower, inner and outer" are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first, second or third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0074] In the present invention, unless otherwise clearly specified and limited, the terms "install, connect, connect" should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection or an integral connection; it can also be a mechanical connection, an electrical connection or a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0075] This embodiment provides a planetary gear reducer for a robot, specifically, Figure 2 As shown, Figure 2 As shown, the reducer includes an inner gear housing 100 and N-stage planetary gear reduction mechanisms 200 arranged in sequence along the axial direction of the inner gear housing 100; N≥2, in this embodiment, N is 3, wherein the first-stage planetary gear reduction mechanism is the high-speed input end of the reducer, the second-stage planetary gear reduction mechanism is the medium-speed stage, and the third-stage planetary gear reduction mechanism is the low-speed output end of the reducer; each stage of the planetary gear reduction mechanism 200 includes a sun gear 201, a planetary gear 202, a planet carrier 203 and a planet shaft 204.

[0076] In order to solve the problems existing in the existing planetary gear reducer, the present embodiment has the following three core designs: A: the planetary gear reducer adopts an overall axial scaled structural design; B: the planetary wheel bearing adopts a three-point contact ball bearing structural design; C: the contact ball bearing structural design at the Nth-stage planet carrier; the following is a detailed introduction to the above three core designs in conjunction with the accompanying drawings:

[0077] A. Overall axial scale structural design

[0078] In an embodiment, Figure 2 As shown, the planetary gear 202 of the first-stage planetary gear reduction mechanism 200 is axially positioned by a retaining ring 300 clamped in a hole inside the inner gear housing 100;

[0079] The sun gear 201 in the second to third stage planetary gear reduction mechanism 200 is provided with a first external tooth 2011 and a second external tooth 2012 along its own axial direction, and the tooth height of the first external tooth 2011 is greater than the tooth height of the second external tooth 2012; the first external tooth 2011 of each stage sun gear 200 is meshed with the planetary gear 202 of the current stage, and the second external tooth 2012 is key-connected with the planetary carrier 203 of the previous stage; the end face of the planetary carrier 203 of the previous stage contacts the end face of the first external tooth 2011 on the sun gear 201 of the current stage;

[0080] The planet shaft 204 of each stage of the planetary gear reduction mechanism is interference fit with the planet shaft mounting hole 206 on the planet carrier 203, and the planet wheel 202 and the planet carrier 203 of the third stage of the planetary gear reduction mechanism are in contact with each other to achieve the axial positioning of the planet wheel in the third stage of the planetary gear reduction mechanism;

[0081] In addition, in order to further reduce the axial size of the reducer, the three-stage planetary gear reduction mechanism in this embodiment shares an internal gear housing 100, and the module of the planetary gear 202 in each stage of the planetary gear reduction mechanism is the same, which can make the width size of the planetary gear 202 in each stage of the planetary mechanism (especially the first stage planetary gear and the second stage planetary gear) thinner.

[0082] B. The planetary gear bearing adopts the structural design of three-point contact ball bearing

[0083] like Figure 2 and Figure 3 As shown, in the 1st to 3rd stage planetary gear reduction mechanism 200, the outer surface of the planetary shaft 204 located in the planetary wheel bearing mounting hole 207 is provided with S first inner ring outer raceways 2041 arranged side by side along the axial direction, S≥2, and a plurality of first steel balls 400 are arranged along the circumferential direction between each first inner ring outer raceway 2041 and the hole wall of the planetary wheel bearing mounting hole 207; the first steel balls 400 installed in each two adjacent first inner ring outer raceways 2041 are staggered in the circumferential direction, thereby constituting the planetary wheel bearing of the N-stage planetary gear reduction mechanism; the planetary wheel bearing mounting hole 207 is provided with an inwardly protruding arc-shaped groove 2042 on the side close to the planet carrier for axial positioning of the first steel ball 400.

[0084] In order to make the positioning of the first steel ball 400 more reliable, Figure 2 and Figure 4 As shown, in this embodiment, S shallow grooves 2071 are also opened on the inner wall of the planetary gear bearing mounting hole 207, and the S shallow grooves 2071 correspond to the S first inner ring outer raceways 2041 one by one. The first inner ring outer raceway 2041 is composed of two eccentrically arranged arcs, which are respectively recorded as the fifth arc and the sixth arc. The first steel ball 400 is in point contact with the two arcs and in contact with the shallow grooves 2071, thereby forming a more reliable three-point contact ball bearing structure.

[0085] C. Contact ball bearing structure design at the Nth stage planet carrier

[0086] like Figure 2 , 6 As shown, the planet carrier 203 of the third-stage planetary gear reduction mechanism is rotationally connected to the inner gear housing 100 via at least one row of contact ball bearing structures (in this embodiment, the contact ball bearing structure is one row), and the contact ball bearing structure realizes the axial positioning of the planet carrier in the third-stage planetary gear reduction mechanism;

[0087] The contact ball bearing structure includes M second inner ring outer raceways 2031 arranged along the axial direction on the outer surface of the planet carrier 203 of the third-stage planetary gear reduction mechanism, and M second outer ring inner raceways 1001 corresponding to the M second inner ring outer raceways 2031 are arranged on the inner wall of the inner gear housing 100 along the axial direction; M≥1;

[0088] M steel ball installation raceways 500 are formed between the M second inner ring outer raceways 2031 and the M second outer ring inner raceways 1001; a plurality of second steel balls 600 are arranged in each steel ball installation raceway along the circumferential direction;

[0089] At least one axial hole 2032 is arranged on the planet carrier 203 of the third-stage planetary gear reduction mechanism, and M ball loading holes 2033 are arranged at positions corresponding to the axial hole 2032 and the second inner ring outer raceway 2031, and each ball loading hole 2033 is provided with an anti-escape structure 700 for preventing the ball from escaping.

[0090] There are many forms of anti-escape structure to choose from. Its purpose is to prevent the second steel ball 600 from falling out of the ball filling hole 2033 during operation, especially under large load conditions after processing. A better way is that not only will the second steel ball 600 not fall out of the ball filling hole 2033 during operation, but also the raceway can be opened to take out the second steel ball 600 when maintenance is needed.

[0091] The ball filling hole 2033 should be set perpendicular to the steel ball mounting raceway 500, that is, perpendicular to the axial hole 2032, which is the best. It can also be set obliquely, but when it is set obliquely, firstly, the processing cost will increase, and secondly, there is a risk of reducing the bearing stiffness.

[0092] Based on the above conditions, two specific structures of the anti-escape structure are provided for reference. The first structure is adopted in this embodiment:

[0093] 1. If Figure 7As shown, a pin 701 is arranged in the ball filling hole 2033, and a limiting hole 702 is arranged on the planetary carrier 203 of the third-stage planetary gear reduction mechanism. The limiting hole 702 is connected with the ball filling hole 2033, and the pin 701 is positioned by installing a tightening screw 703 in the limiting hole 702. The limiting hole 702 is preferably parallel to the central axis of the axial hole 2032, so that the force is relatively balanced when the limiting and tightening is performed. The pin 701 is fixed. If the contact ball bearing structure is multi-row, the limiting holes 702 should be staggered, and the limiting holes closer to the center row are deeper. In this case, the axial hole 2032 should be equal to the number of raceways.

[0094] The processing and assembly method of the contact ball bearing structure in this embodiment is as follows:

[0095] Step 1: Processing M second outer ring inner raceways 1001 on the inner gear housing 100;

[0096] Step 2: The axial hole 2032, M ball loading holes 2033 and M limiting holes 702 are processed on the planet carrier 203 of the third-stage planetary gear reduction mechanism; after the axial hole 2032, M ball loading holes 2033 and M limiting holes 702 are manufactured, the pins 701 are respectively installed in the M ball loading holes 2032, and then the limiting devices are installed through the limiting holes 702 to fix the pins 701. After fixing, the pins 701 are processed so that the ends of the pins 701 away from the second outer ring inner raceway 1001 are coplanar with the hole wall of the axial hole 2032;

[0097] Alternatively, first make M ball filling holes 2032 and M limiting holes 702 on the planet carrier 203 of the third-stage planetary gear reduction mechanism; after the M ball filling holes 2032 and the M limiting holes 702 are made, the pins 701 are all installed in the M ball filling holes 2032, and then the limiting devices are installed through the limiting holes 702 to fix the pins 701. After fixing, the axial holes 2032 are made so that the end of each pin 701 away from the second outer ring inner raceway 1001 is coplanar with the hole wall of the axial hole 2032;

[0098] Step 3: Process the M second inner ring outer raceways 2031 on the planet carrier 203 of the third-stage planetary gear reduction mechanism, and at the same time process the pins 701 extending into the second inner ring outer raceway 2031 through the ball filling holes 2032, so that one end of each pin 701 extending into the second inner ring outer raceway 2031 is coplanar with the wall of the second inner ring outer raceway 2031; after the production is completed, remove the pins 701 and the limiting device;

[0099] Step 4: Load the second steel ball 600. There are two ways to do this:

[0100] Method 1:

[0101] Step 4.1: Load a second steel ball 600 into a raceway through the ball loading hole 2032 made in step 3; grease may be applied to the second steel ball 600 and / or the raceway to reduce the difficulty of installation;

[0102] Step 4.2: Rotate the inner gear housing 100 so that the second steel ball 600 loaded in step 4.1] is offset from the ball loading hole 2032;

[0103] Step 4.3: Load a second steel ball 600 into the raceway through the ball loading hole 2032;

[0104] Step 4.4: loop steps 4.2 to 4.3 until all the second steel balls 600 are loaded into the raceway;

[0105] Step 4.5: Repeat steps 4.1 to 4.4 to load other raceways until all are loaded;

[0106] Method 2:

[0107] Step 4.1: Load a second steel ball 600 into each raceway through the ball loading hole 2032 made in step 3;

[0108] Step 4.2: Rotate the inner gear housing 100 so that the second steel balls 600 loaded in step 4.1 are staggered from the ball loading holes 2032;

[0109] Step 4.3: Load a second steel ball 600 into each raceway through the ball loading hole 2032;

[0110] Step 4.4: Repeat steps 4.2 to 4.3 until all the second steel balls 600 are loaded into each raceway;

[0111] Step 5: Install the pin shaft 701 into the ball filling hole 2032 to seal it, and insert the limiting device into the limiting hole 702 to fix the pin shaft 701.

[0112] 2. An isosceles trapezoidal elastic sleeve is arranged in the ball filling hole, with the bottom surface with a larger area of ​​the sleeve facing the center of the bearing, and the top surface with a smaller area facing the outer raceway of the second inner ring. The diameter of the larger area is larger than the diameter of the second steel ball, and the diameter of the smaller area is smaller than the diameter of the second steel ball. However, the difference must ensure that the deformation generated during installation can squeeze the second steel ball in, and at the same time, the strength can ensure that the second steel ball is not squeezed out when the second steel ball is subjected to force at this position during operation.

[0113] In this embodiment, when the number M of the steel ball installation raceway 500 is 1: the steel ball installation raceway 500 includes four eccentric arcs, each of which occupies 1 / 4 of the circumference of the cross section, and the second steel ball 600 is in point contact with the four arcs of the steel ball installation raceway 500. Figure 8 As shown, each second outer ring inner raceway 1001 is composed of a first arc A1 and a second arc A2 that are eccentrically arranged, and the second steel ball 600 is in point contact with the first arc A1 and the second arc A2, respectively, and the contact points here are recorded as S1 and S2 respectively; each second inner ring outer raceway 2031 is composed of a third arc A3 and a fourth arc A4 that are eccentrically arranged, and the second steel ball 600 is in point contact with the third arc A3 and the fourth arc A4, respectively, and the contact points here are recorded as S3 and S4 respectively, thereby forming a four-point contact ball bearing structure. In order to further reduce steel ball wear, the contact points of the second steel ball 600 with the first arc, the fourth arc, and the center of the second steel ball 600 are collinear (such as Figure 8 As shown, that is, S1, S4, O are collinear); the contact points of the second steel ball 600 with the second arc, the third arc, and the center of the second steel ball 600 are collinear (as shown Figure 8 As shown, points S2, S3 and O are collinear).

[0114] When the number M of steel ball installation raceway 500 is 2, there are three structural forms:

[0115] The first form is:

[0116] The first steel ball installation raceway includes four eccentric arcs, each of which occupies 1 / 4 of the circumference of the cross section; the second steel ball installation raceway includes four eccentric arcs, each of which occupies 1 / 4 of the circumference of the cross section; the arc of the first steel ball installation raceway is the same as the arc of the second steel ball installation raceway, and the second steel ball 600 and the four arcs of the first steel ball installation raceway, as well as the second steel ball 600 and the four arcs of the second steel ball installation raceway are all point contacts, such as Figure 8 As shown;

[0117] The second and third forms are:

[0118] The first steel ball installation raceway includes two eccentric arcs, each of which occupies 1 / 2 of the circumference of the cross section; the second steel ball installation raceway includes two eccentric arcs, each of which occupies 1 / 2 of the circumference of the cross section; the arc of the first steel ball installation raceway and the arc of the second steel ball installation raceway are mirror images, and the structure presented is a back-to-back mirror image (such as Fig. 9 ), or face-to-face mirroring (as Fig.10 shown).

[0119] like Fig.11As shown, when the number M of steel ball mounting raceways is 3, the first steel ball mounting raceway includes two eccentric arcs, each of which occupies 1 / 2 of the circumference of the cross-section; the second steel ball mounting raceway includes four eccentric arcs, each of which occupies 1 / 4 of the circumference of the cross-section, and the second steel ball is in point contact with the four arcs of the second steel ball mounting raceway; the third steel ball mounting raceway includes two eccentric arcs, each of which occupies 1 / 2 of the circumference of the cross-section; the arc of the first steel ball mounting raceway and the arc of the third steel ball mounting raceway are mirrored.

[0120] In addition to the above three cores, in order to be applicable to different usage scenarios, the present embodiment realizes that the motor used in conjunction with the reducer can be installed on both the high-speed side (power input side) and the low-speed side (power output side) through the special design of each stage sun gear and the Nth stage planet carrier. The specific structure is as follows: Fig.13 and Fig.14 As shown:

[0121] Each stage sun gear 201 has a central through hole 2013. A keyway for connecting to an external motor output terminal is provided in the central through hole 2013 of the sun gear 201 of the first stage planetary gear reduction mechanism. A positioning through hole 2034 for installing a motor is provided at the center of the planet carrier 203 of the third stage planetary gear reduction mechanism. When the motor is arranged on the high speed side, such as Fig.13 As shown, the external motor is close to the first stage planetary gear reduction mechanism, and the output end of the motor is directly connected to the sun gear key of the first stage planetary gear reduction mechanism. When the motor is set on the high speed side, such as Fig.14 As shown, the motor is close to one side of the Nth-stage planetary gear reduction mechanism. After the motor is positioned through the motor positioning through hole, the output end of the motor passes through the sun gear of the second-stage planetary gear reduction mechanism and is key-connected with the sun gear of the first-stage planetary gear reduction mechanism.

Claims

1. A planetary gear reducer for a robot, comprising an inner gear housing and N-stage planetary gear reduction mechanisms arranged in sequence along the axial direction of the inner gear housing; N≥2; each stage of the planetary gear reduction mechanism comprises a sun gear, a planetary gear, a planet carrier and a planetary shaft; Features: The planetary gear of the first-stage planetary gear reduction mechanism is axially positioned by a retaining ring through a hole clamped inside the internal gear housing; In the 2nd to Nth stage planetary gear reduction mechanisms, the sun gear is provided with a first external tooth and a second external tooth, and the tooth height of the first external tooth is greater than the tooth height of the second external tooth; the first external tooth is meshed with the planetary gear of the current stage, and the second external tooth is key-connected with the planetary carrier of the previous stage; The end face of the previous stage planet carrier contacts the end face of the first external tooth on the current stage sun gear, and at the same time forms a micro gap with the end face of the current stage planet gear; The planet shaft of each stage of the planetary gear reduction mechanism is interference fit with the planet shaft mounting hole on the planet carrier, and the planetary gear and the planet carrier of the Nth stage of the planetary gear reduction mechanism are in contact with each other to achieve the axial positioning of the planetary gear in the Nth stage of the planetary gear reduction mechanism; In the 1st to Nth stage planetary gear reduction mechanism, the outer surface of the planetary shaft located in the planetary wheel bearing mounting hole is provided with S first inner ring outer raceways arranged side by side in the axial direction, S≥2, and a plurality of first steel balls are arranged along the circumferential direction between each first inner ring outer raceway and the hole wall of the planetary wheel bearing mounting hole; the first steel balls installed in each two adjacent first inner ring outer raceways are arranged in a staggered manner in the circumferential direction, thereby forming the planetary wheel bearing of the Nth stage planetary gear reduction mechanism; a circular arc groove protruding inward is provided on the side of the planetary wheel bearing mounting hole close to the planet carrier, which is used to axially position the first steel balls; The planet carrier of the Nth-stage planetary gear reduction mechanism is rotationally connected to the inner gear housing via at least one row of contact ball bearing structures, and the contact ball bearing structure realizes axial positioning of the planet carrier in the Nth-stage planetary gear reduction mechanism; The contact ball bearing structure includes M second inner ring outer raceways arranged along the axial direction on the outer surface of the planet carrier of the N-th stage planetary gear reduction mechanism, and M second outer ring inner raceways corresponding to the M second inner ring outer raceways are arranged on the inner wall of the inner gear housing along the axial direction; M≥1; M steel ball installation raceways are formed between the M second inner ring outer raceways and the M second outer ring inner raceways; a plurality of second steel balls are arranged in the circumferential direction in each steel ball installation raceway; The planet carrier of the Nth-stage planetary gear reduction mechanism is provided with at least one axial hole, and M ball loading holes are provided at positions corresponding to the axial hole and the outer raceway of the second inner ring, and each ball loading hole is provided with an anti-escape structure to prevent the ball from escaping; A keyway for connecting with an output end of an external motor is arranged in the central through hole of the sun wheel of the first-stage planetary gear reduction mechanism.

2. The planetary gear reducer for robots according to claim 1, characterized in that: Each stage of the sun gear has a central through hole; the center of the planet carrier of the Nth stage planetary gear reduction mechanism is provided with a positioning through hole for installing the motor, and a keyway is provided in the central through hole of the sun gear in the first stage planetary reduction gear mechanism.

3. The planetary gear reducer for robots according to claim 2, characterized in that: A limiting hole is also provided on the planet carrier of the Nth-stage planetary gear reduction mechanism, and the limiting hole is connected to the ball loading hole; a limiting device for preventing the anti-escape structure from moving is provided in the limiting hole.

4. The planetary gear reducer for robots according to claim 3, characterized in that: The limiting hole is a screw hole parallel to the axial hole, and the limiting device is a tightening screw.

5. The planetary gear reducer for robots according to any one of claims 1 to 4, characterized in that: When M is 1: the steel ball mounting raceway includes four eccentric arcs, each of which occupies 1 / 4 of the circumference of the cross section, and the second steel ball is in point contact with the four arcs of the steel ball mounting raceway.

6. The planetary gear reducer for robots according to any one of claims 1 to 4, characterized in that: When M is 2, The first ball installation raceway consists of four eccentric arcs, each of which occupies 1 / 4 of the cross-section circumference; The second ball installation raceway consists of four eccentric arcs, each of which occupies 1 / 4 of the circumference of the cross section; The arc of the first steel ball mounting raceway is the same as the arc of the second steel ball mounting raceway, and the second steel ball is in point contact with the four arcs of the first steel ball mounting raceway, as well as the second steel ball and the four arcs of the second steel ball mounting raceway.

7. The planetary gear reducer for robots according to any one of claims 1 to 4, characterized in that: When M is 2, The first ball installation raceway consists of two eccentric arcs, each of which occupies 1 / 2 of the cross-section circumference; The second ball installation raceway consists of two eccentric arcs, each of which occupies 1 / 2 of the circumference of the cross section; The arc of the first steel ball mounting raceway and the arc of the second steel ball mounting raceway are mirror images.

8. The planetary gear reducer for robots according to any one of claims 1 to 4, characterized in that: When M is 3, The first ball installation raceway consists of two eccentric arcs, each of which occupies 1 / 2 of the cross-section circumference; The second steel ball installation raceway includes four eccentric arcs, each of which occupies 1 / 4 of the circumference of the cross section. The second steel ball is in point contact with the four arcs of the second steel ball installation raceway. The third ball installation raceway consists of two eccentric arcs, each of which occupies 1 / 2 of the circumference of the cross section; The arc of the first steel ball installation raceway and the arc of the third steel ball installation raceway are mirror images.

9. The planetary gear reducer for robots according to claim 1, characterized in that: The inner wall of the planet wheel bearing mounting hole of each stage of the planetary gear reduction mechanism is provided with S shallow grooves, and the S shallow grooves correspond one by one to the S first inner ring outer raceways; the first inner ring outer raceway is composed of a first circular arc and a second circular arc which are eccentrically arranged, and the first steel ball contacts the first circular arc and the second circular arc respectively, and contacts the shallow grooves, thereby forming a three-point contact ball bearing structure.

10. The planetary gear reducer for robots according to claim 1, characterized in that: N-stage planetary gear reduction mechanisms share an internal gear housing, and the modules of the planetary gears in each stage of the planetary gear reduction mechanism are the same.

Images