Internal meshing RV-C type reducer for precise control

Abstract

The present invention discloses an internal meshing RV-C type reducer for precision control, which relates to the technical field of robot reducers, including an inner cycloid gear ring and a two-stage reduction component placed therein: the first-stage reduction component includes a driving wheel, a duplex gear and a planetary gear on a servo motor, and the second-stage reduction component includes 2 to 3 evenly distributed eccentric shafts, a cycloid wheel, a left rigid disk and a right rigid disk. After the cycloid wheel is modified, the lateral clearance between the inner cycloid teeth and the cycloid tooth grooves is 0.1λ1≤Δc<0.7λ1, where λ1 is the theoretical radial thermal expansion of the cycloid wheel when doing work under rated torque. The cycloid wheel modification of the present invention satisfies the relationship between the lateral clearance Δc and the thermal expansion of the cycloid wheel, and thus has good dynamic characteristics, less heat generation, less wear; conventional manufacturing precision, low cost; and can be interchanged with existing RV reducers.

Description

Technical Field

[0001] The present invention relates to the technical field of robot reducers, and particularly to an internal meshing RV-C type reducer for precise control with good dynamic characteristics. Background Art

[0002] Robots are the pearls at the crown of the manufacturing industry and an important symbol to measure a country's scientific and technological innovation and high-end manufacturing level. The RV reducer is one of the most core components of robots and is also the only component that has not been truly domesticated.

[0003] There are two existing lateral clearance technologies for the cycloid gear after modification in RV reducers. One is patents such as CN 110966357 A, CN111059225 A, CN 110985611 A, CN 110985610 A, etc. Since their lateral clearances are set based on the calculation parameters of the theoretical thermal expansion amount, their thermal expansion coefficient αt = 1.379·10 -5 (1 / ℃) comes from the data on page 95 of "Research on Thermal Expansion of Precision Parts and Accurate Thermal Expansion Coefficient of Materials" (Miao Enming, Hefei University, September 2004), which is measured from the actual thermal expansion amount of the solid round bar-shaped structure bearing steel material. The actual cycloid gear structure is a porous disc-shaped structure, which is very different from the solid round bar-shaped structure of the theoretical measurement sample. According to the quasi-harmonic approximation theory in "Introduction to Solid State Physics" (Kittel C [USA], Beijing: Science Press, 1979), thermal deformation is inseparable from the shape factor. At the same time, through the comparative research on the actual measurement of the thermal expansion of the existing structure and different structure cycloid gear bearing steel materials, it is confirmed that there are significant differences in the thermal expansion coefficients of the porous disc-shaped structure bearing steel material and the solid round bar-shaped structure bearing steel material. Therefore, it will be difficult to meet the design requirements when implementing the above existing patented technologies.

[0004] The other is patents such as CN 108869644 A and CN 106641110 A, etc., which do not make a quantitative setting for specifically defining the lateral clearance range of the cycloid gear, and only give a principle description that if the lateral clearance is too small, it will cause wear and heat generation, poor dynamic performance, shortened life, etc. during temperature rise and expansion. This kind of principle knowledge is well-known to those of ordinary skill in the art. Summary of the Invention

[0005] The object of the present invention is to propose the correct relational formula between the lateral clearance Δc after modification of the cycloid gear and the thermal expansion amount, so as to solve the defects such as easy heat generation, easy wear, and poor accuracy retention in the existing technology, and provide an internal meshing RV-C type reducer for precise control with good dynamic characteristics.

[0006] To solve the above technical problems, a technical solution adopted by the present invention is:

[0007] Provided is an internal meshing RV-C type reducer for precise control, including an internal cycloid gear ring and a two-stage reduction component disposed therein: The first-stage reduction component includes a driving wheel on a servo motor, a double gear, and a planetary gear. The double gear includes a driven wheel and a sun gear. The driven wheel meshes with the driving wheel, the sun gear meshes with the planetary gear, the planetary gear is connected to the eccentric shaft extension end of the second-stage reduction component, a through wire tube is arranged in the inner hole of the double gear, and both sides of the double gear are respectively supported at corresponding positions of the right rigid disk and the robot body by a first bearing and a second bearing; The second-stage reduction component includes 2 to 3 evenly distributed eccentric shafts, cycloid wheels, a left rigid disk, and a right rigid disk. Needle bearings for supporting the cycloid wheels are arranged on two eccentric segments of the eccentric shaft. The two shaft extensions on both sides of the eccentric segment of the eccentric shaft are respectively supported in the peripheral holes of the left and right rigid disks by second and first tapered roller bearings. The left and right rigid disks are respectively supported in the inner holes on both sides of the internal cycloid gear ring by main bearings. The evenly distributed flanges on the left rigid disk pass through the corresponding through holes on the cycloid wheels and are connected to the right rigid disk with screws and positioning pins to form a rigid body. The cycloid wheel includes a left cycloid wheel and a right cycloid wheel, and adopts "equidistant - shift distance" modification, so that a lateral clearance Δc and a radial clearance are formed between the internal cycloid teeth and the cycloid tooth grooves.

[0008] (1) When λ1 is the theoretical radial thermal expansion amount of the cycloid wheel when the reducer does work:

[0009] The range of the lateral clearance Δc between the internal cycloid teeth and the cycloid tooth grooves on one side is: 0.1λ1 ≤ Δc < 0.7λ1;

[0010] (2) When λ2 is the actual radial thermal expansion amount of the cycloid wheel when the reducer does work:

[0011] The lateral clearance Δc between the internal cycloid teeth and the cycloid tooth grooves on one side is Δc = (0.1 - 5)λ2;

[0012] (3) When λ is the actual lateral thermal expansion amount of the cycloid wheel when the reducer does work:

[0013] The lateral clearance Δc between the internal cycloid teeth and the cycloid tooth grooves on one side is Δc = (0.1 - 5)λ.

[0014] In a preferred embodiment of the present invention, the lateral clearance Δc between the internal cycloid teeth and the cycloid tooth grooves on one side is Δc = (0.2 - 0.6)λ1.

[0015] In a preferred embodiment of the present invention, the lateral clearance Δc between the internal cycloid teeth and the cycloid tooth grooves on one side is Δc = (0.1 - 4)λ2.

[0016] In a preferred embodiment of the present invention, the lateral clearance Δc between the internal cycloid teeth and the cycloid tooth grooves on one side is Δc = (0.2 - 3)λ2.

[0017] In a preferred embodiment of the present invention, the lateral clearance Δc between the inner cycloid tooth and the cycloid tooth groove on one side is Δc = λ2.

[0018] In a preferred embodiment of the present invention, the range of the lateral clearance between the inner cycloid tooth and the cycloid tooth groove on one side is: 0.1λ2 ≤ Δc < 0.7λ2.

[0019] In a preferred embodiment of the present invention, the lateral clearance Δc between the inner cycloid tooth and the cycloid tooth groove on one side is Δc = (0.2 - 0.6)λ2.

[0020] In a preferred embodiment of the present invention, the lateral clearance Δc between the inner cycloid tooth and the cycloid tooth groove on one side is Δc = (0.1 - 4)λ.

[0021] In a preferred embodiment of the present invention, the lateral clearance Δc between the inner cycloid tooth and the cycloid tooth groove on one side is Δc = (0.2 - 3)λ.

[0022] In a preferred embodiment of the present invention, the lateral clearance Δc between the inner cycloid tooth and the cycloid tooth groove on one side is Δc = λ.

[0023] In a preferred embodiment of the present invention, the range of the lateral clearance between the inner cycloid tooth and the cycloid tooth groove on one side is: 0.1λ ≤ Δc < 0.7λ.

[0024] In a preferred embodiment of the present invention, the lateral clearance Δc between the inner cycloid tooth and the cycloid tooth groove on one side is Δc = (0.2 - 0.6)λ.

[0025] In a preferred embodiment of the present invention, the shape of the through hole is a quasi-sector structure, or expansion-reducing holes are provided on both sides of the through hole, and the shape of the expansion-reducing holes is circular or polygonal or irregular.

[0026] In a preferred embodiment of the present invention, the theoretical radial thermal expansion amount λ1 of the cycloid gear is λ1 = (d0 Δt) αt1, the actual radial thermal expansion amount λ2 of the cycloid gear is λ2 = (d0 Δt) αt2, and the actual lateral thermal expansion amount λ of the cycloid gear is λ = (d0 Δt) αt, where αt, αt1, and αt2 are the actual lateral thermal expansion coefficient, theoretical radial thermal expansion coefficient, and actual radial thermal expansion coefficient of the cycloid gear bearing steel respectively, Δt is the temperature rise of the cycloid gear, d0 is the average diameter of the addendum circle and the dedendum circle of the cycloid gear, and αt1 = 1.38·10 -5 (1 / °C), the temperature rise Δt = 45°C, and λ1 = (d0 Δt) αt = 0.00062d0.

[0027] The beneficial effects of the present invention are:

[0028] (1) The lateral clearance Δc generated by the "equal pitch - shifted pitch" modification adopted by the present invention is closely related to the thermal expansion of the cycloid gear, thus having good dynamic characteristics and not overheating when operating under rated load.

[0029] (2) The present invention adopts conventional manufacturing precision, with simple process and low cost.

[0030] (3) The external dimensions of the present invention are the same as those of common RV reducers and can be interchanged with them. Description of the Drawings

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings, where:

[0032] Figure 1 is a schematic cross - sectional view of the structure of a preferred embodiment of an internal - meshing RV - C type reducer for precision control of the present invention;

[0033] Figure 2 is a schematic structural view of a cycloid gear in a preferred embodiment of an internal - meshing RV - C reducer for precision control of the present invention;

[0034] Figure 3 is a schematic structural view of another preferred embodiment of a cycloid gear in an internal - meshing RV - C reducer for precision control of the present invention;

[0035] In the figure: 1, internal cycloid gear ring; 2, main bearing; 3, left cycloid gear; 4, right cycloid gear; 5, right rigid disk; 6, driven wheel; 7, sun gear; 8, double - joint gear; 9, first bearing; 10, second bearing; 11, eccentric shaft; 12, planetary gear; 13, driving wheel; 14, first tapered roller bearing; 15, second tapered roller bearing; 16, left rigid disk; 17, through - hole; 18, anti - expansion hole. Detailed Embodiments

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0037] Please refer to Figures 1-3 , the embodiments of the present invention include:

[0038] A precision control internal meshing RV-C type reducer, which includes an internal cycloid gear ring and two-stage reduction components disposed therein:

[0039] The first-stage reduction component includes a driving wheel on a servo motor, a double gear, and a planetary gear. The double gear includes a driven wheel and a sun gear. The driven wheel meshes with the driving wheel, the sun gear meshes with the planetary gear, the planetary gear is connected to the eccentric shaft extension end of the second-stage reduction component, a through wire tube is arranged in the inner hole of the double gear, and both sides of the double gear are respectively supported on corresponding positions of the right rigid disk and the robot body by a first bearing and a second bearing;

[0040] The second-stage reduction component includes 2 to 3 uniformly distributed eccentric shafts, cycloid wheels, a left rigid disk, and a right rigid disk. Needle bearings for supporting the cycloid wheels are arranged on two eccentric sections of the eccentric shaft. The two sides of the eccentric section of the eccentric shaft are respectively supported in peripheral holes of the left and right rigid disks by tapered roller bearings. The left and right rigid disks are respectively supported in inner holes on both sides of the internal cycloid gear ring by main bearings. Flanges uniformly distributed on the left rigid disk pass through corresponding through holes on the cycloid wheels and are connected to the right rigid disk by screws and positioning pins to form a rigid body. The cycloid wheel includes a left cycloid wheel and a right cycloid wheel, and adopts "equal pitch - shift pitch" modification, so that a lateral clearance Δc and a radial clearance are formed between the internal cycloid teeth and the cycloid tooth grooves. Among them, when performing the modification, "positive equal pitch - positive shift pitch" modification is preferably adopted first, and "negative equal pitch - negative shift pitch" modification can be selected secondly.

[0041] When λ1 is the theoretical radial thermal expansion amount of the cycloid wheel when the reducer does work:

[0042] The range of the lateral clearance Δc is: 0.1λ1 ≤ Δc < 0.7λ1.

[0043] The shape of the through hole on the cycloid wheel can be a quasi-sector structure, or expansion-reducing holes are opened on both sides of the through hole, and the shape of the expansion-reducing hole can be circular or polygonal or irregular.

[0044] According to the discovery in the theory of thermal expansion research that thermal deformation is inseparable from shape factors, through the actual measurement and comparative research on the thermal expansion coefficients of bearing steel materials of cycloid wheels with different structures, it is found that there are differences in the thermal expansion coefficients of bearing steel materials of cycloid wheels with different structures. Especially, the change in the through hole structure or the structure around the through hole of the cycloid wheel has an impact on the thermal expansion of the cycloid wheel. Therefore, reasonably setting the cycloid wheel structure, especially reasonably setting the through hole or the structure around the through hole, to minimize the thermal expansion amount of the cycloid wheel will be most beneficial to the precision design of the reducer. Through a large number of thermal expansion ratio comparison studies on cycloid wheels with different structures, on the premise of ensuring the stiffness of the cycloid wheel, the through hole of the cycloid wheel is set from the existing circular or fan-shaped structure to a quasi-sector shape, that is, the through hole is expanded to both sides of the fan to form a quasi-sector; or expansion-reducing holes are opened on both sides of the through hole, and the shape of the expansion-reducing hole is a circular or polygonal or irregular structure.

[0045] Therefore,

[0046] (1) When λ2 is the actual radial thermal expansion of the cycloid gear when the reducer does work:

[0047] The lateral clearance Δc between the inner cycloid tooth and the cycloid tooth groove on one side = (0.1 - 5)λ2;

[0048] (2) When λ is the actual lateral thermal expansion of the cycloid gear when the reducer does work:

[0049] The lateral clearance Δc between the inner cycloid tooth and the cycloid tooth groove on one side = (0.1 - 5)λ.

[0050] Among them, the actual radial thermal expansion of the cycloid gear can be obtained by measuring the thermal expansion, or by calculating after measuring the thermal expansion coefficient, that is, λ2 = (d0 Δt) αt2, and it can also be calculated and deduced from the actual lateral thermal expansion; the actual lateral thermal expansion of the cycloid gear can be obtained by measuring the thermal expansion, or by calculating after measuring the thermal expansion coefficient, that is, λ = (d0 Δt) αt, and it can also be calculated and deduced from the actual radial thermal expansion; among them, αt and αt2 are the thermal expansion coefficients of the cycloid gear bearing steel, Δt is the temperature rise of the cycloid gear, and d0 is the average diameter of the addendum circle and the dedendum circle of the cycloid gear.

[0051] According to the quasi - harmonic approximation theory in "Introduction to Solid State Physics" (Charles Kittel [USA], Beijing: Science Press, 1979), the mechanism of thermal expansion is that solids are composed of tiny crystals, and crystals are formed by atoms arranged in a certain position in space. There is both potential energy and kinetic energy between atoms. When the atoms are in equilibrium, the sum of their kinetic energy and potential energy is the smallest. As the temperature rises, the kinetic energy of the atoms increases, which promotes the increase in the displacement between atoms and the increase in potential energy. Macroscopically, it is manifested as the occurrence of thermal expansion. Thermal expansion can be regarded as an object being subjected to a uniform outward expansion force. Therefore, the thermal expansion is closely related to the shape of the object.

[0052] According to the research in "Research on the Influence of Shape Parameters on the Thermal Expansion of Parts" (Miao Enming, Fei Yetai, Journal of Applied Sciences, 2003.06), it is found that thermal deformation is inseparable from shape factors; the calculation of thermal expansion coefficients usually includes simple calculation methods, statistical calculation methods, and Grüneisen formulas, etc. These methods all have certain limitations, which makes the calculated thermal expansion coefficient value differ greatly from the actual measured value. The currently used thermal expansion coefficient is still the actual measured value of a round bar of a certain size, which inevitably makes the measured value of the thermal expansion coefficient contain the influence of shape factors.

[0053] According to the search on page 95 of "Research on Thermal Expansion of Precision Parts and Precise Thermal Expansion Coefficient of Materials" (Miao Enming, Hefei University, 2004.09), the thermal expansion coefficient of bearing steel αt = 1.38·10-5 (1 / ℃) is the measured value of solid round bar structural bearing steel material of a certain size.

[0054] According to the linear expansion coefficient and density table of commonly used materials in the "Chinese Mechanical Design Encyclopedia (Volume 1)" (Table 12.2-4), the linear expansion coefficient αt table of materials in the "Mechanical Design Manual (Volume 1)" (Table 1-1-12), and the linear expansion coefficient table of commonly used materials in the "Modern Mechanical Design Manual (Volume 1)" (Table 1-1-12), the linear expansion coefficient of chromium steel at 20℃~100℃ is αt =1.12·10 -5 , only the thermal expansion coefficient of bearing steel αt =1.38·10 -5 (1 / ℃) is 81.12%.

[0055] According to the national standard GB / T 36491-2018 "General Technical Requirements for Cycloidal Pinwheel Planetary Gear Transmission Devices for Robots", the maximum temperature of the reducer housing should not exceed 60°C, and the operating environment should be between -10°C and 40°C. The specific value of the cycloidal wheel temperature rise can be calculated by the temperature difference between the reducer housing and the environment and the temperature difference between the housing and the cycloidal wheel, or it can be directly taken as 45°C. When the cycloidal wheel temperature rise is 45°C, because the reducer generally works in a room temperature environment, the corresponding set cycloidal wheel thermal expansion is also high.

[0056] The actual structure of the cycloid wheel is a porous disc structure, which is far from the solid round rod structure of the theoretical measured sample. Therefore, the actual thermal expansion coefficient of the bearing steel material of the cycloid wheel will be lower than the theoretical thermal expansion coefficient of the bearing steel material.

[0057] By applying relevant thermal expansion research theories and through actual measurement research on the thermal expansion coefficient of cycloidal wheel bearing steel materials with existing structures and different structures, it is also confirmed that the actual thermal expansion coefficient of cycloidal wheel bearing steel materials with existing structures and different structures is lower than the theoretical thermal expansion coefficient of bearing steel materials.

[0058] In summary, the theoretical thermal expansion amount, thermal expansion coefficient and temperature rise of the cycloid wheel are all greater than the actual thermal expansion amount, thermal expansion coefficient and temperature rise. In order to obtain the correct lateral clearance, the actual thermal expansion amount, or the thermal expansion coefficient and temperature rise data of the cycloid wheel can be measured by various existing means, and the thermal expansion amount can be multiplied by a certain coefficient to adjust it, so as to obtain the parameters of the actual lateral clearance Δc.

[0059] Those of ordinary skill in the art, although the amount of thermal expansion, coefficient of thermal expansion, temperature, and the coefficient multiplied are different from those of this patent, but the final value of the lateral clearance Δc falls within the claims of this patent, and is still included in the scope of this right protection. Similarly, since this patent has set the value range of the actual lateral thermal expansion amount, if the theoretical lateral thermal expansion amount derived from the theoretical radial thermal expansion amount has no practicality and is covered by the practicality of the actual lateral thermal expansion amount, and at the same time the theoretical lateral thermal expansion amount can be directly derived from the theoretical radial thermal expansion amount, the value of the theoretical lateral thermal expansion amount is included in the patent protection scope of this invention.

[0060] In some of the prior arts, due to reasons such as the relatively large values of the theoretical coefficient of thermal expansion, temperature rise, and adjustment coefficient adopted, the value of the lateral clearance Δc is too large, resulting in poor accuracy.

[0061] In some of the prior arts, due to the too small value of the lateral clearance Δc, the cycloid gear and the internal cycloid gear ring are in interference friction, and inevitably there is a problem of poor dynamic performance. To further illustrate this problem, take the RV reducer national 863 project jointly tackled by a famous expert from Dalian Jiaotong University and CRRC Qishuyan Institute as an example. The parameters publicly published in September 2017 are as follows: Rz = 77, e = 1.50, Za = 39, K1 = 0.7792, Δrz = -0.027, ΔRz = -0.047, backlash 0.29'.

[0062] When the backlash = 0.29' remains unchanged, through calculation, it is known that:

[0063] The lateral clearance ΔC = 0.003 (mm).

[0064] And the theoretical radial thermal expansion amount of the cycloid gear λ1 = (d0Δt)αt = 0.00062d0 (mm) = 0.09548 (mm). When the temperature rise Δt = 45°C, in the formula: the thermal expansion coefficient of bearing steel GCr15 αt = 1.38·10 -5 (1 / °C), d0 is the average diameter of the addendum circle and the dedendum circle of the cycloid gear.

[0065] Furthermore, through calculation, it is obtained that the actual radial thermal expansion amount λ2 of the cycloid gear is less than the theoretical radial thermal expansion amount λ1, that is, λ2 < λ1.

[0066] Furthermore, through calculation, it is obtained that the actual radial thermal expansion amount λ2 of the cycloid gear is less than the actual lateral thermal expansion amount λ, that is, λ2 < λ, where λ is the actual lateral thermal expansion amount of the cycloid gear when the reducer does work under the rated torque.

[0067] At the same time, it is obtained that the actual lateral thermal expansion amount λ of the cycloid gear is less than the theoretical radial thermal expansion amount λ1, that is, λ < λ1.

[0068] Therefore, it is concluded that the lateral clearance ΔC is less than the set 0.1λ2, less than the set 0.1λ, less than the set 0.1λ1, less than the actual radial thermal expansion λ2, less than the actual lateral thermal expansion λ, and less than the theoretical radial thermal expansion λ1, that is, ΔC < 0.1λ2 < 0.1λ < 0.1λ1 < λ2 < λ < λ1.

[0069] From this, it can be known that the lateral clearance ΔC of this project is less than the actual lateral thermal expansion λ, that is, ΔC < λ, and does not satisfy Δc = (0.1 - 5)λ, does not satisfy 0.1λ1 ≤ Δc < 0.7λ1, and does not satisfy Δc = (0.1 - 5)λ2. Therefore, there must be interference friction between the cycloid gear and the internal cycloid gear ring, and problems such as heat generation, wear, and accuracy decline in dynamic performance will inevitably occur.

[0070] The usage effects of the reducer at different lateral clearances are shown in the following table.

[0071]

[0072] As can be seen from the above table:

[0073] Performance 1: When the lateral clearance Δc satisfies 0.1λ1 ≤ Δc < 0.7λ1, it meets the standard;

[0074] Performance 2: When the lateral clearance Δc = (0.1 - 5)λ2, it meets the standard;

[0075] Performance 3: When the lateral clearance Δc = (0.7 - 5)λ1 and Δc < 0.1λ1, Δc > 5λ1, it does not meet the standard;

[0076] Performance 4: When the lateral clearance Δc < 0.1λ2 and Δc > 5λ2, it does not meet the standard;

[0077] Performance 5: Under the condition of meeting the standard, the temperature rise is lower than 45°C.

[0078] Therefore, in summary, the above table can more intuitively show the technical effects achieved by the improvement points of this application from the perspective of actual detection, that is:

[0079] (1) When the theoretical radial thermal expansion λ1 is adopted, the lateral clearance needs to satisfy 0.1λ1 ≤ Δc < 0.7λ1 to effectively reduce the heat generation caused by wear. At the same time, the accuracy of the reducer can be maintained at a relatively high level;

[0080] (2) When the actually measured radial thermal expansion λ2 is obtained, since the actually measured radial thermal expansion is generally less than the theoretical radial thermal expansion, the lateral clearance only needs to satisfy Δc = (0.1 - 5)λ2 to meet the requirements of reducing the temperature rise, reducing wear, extending the service life, and maintaining high precision.

[0081] (3) When the measured lateral thermal expansion amount is λ, since the measured lateral thermal expansion amount is generally smaller than the theoretical radial thermal expansion amount, the lateral clearance can meet the requirements of reducing temperature rise, reducing wear, extending service life, and maintaining high precision only when Δc = (0.1 - 5)λ.

[0082] Similarly, through theoretical calculation and actual measurement research on the thermal expansion coefficients of cycloid gears with different structures, it is deduced that the lateral clearance Δc between the internal cycloid teeth and the cycloid tooth groove on one side must satisfy the formula 0.1λ1 ≤ Δc < 0.7λ1, and through actual sample operation tests, it conforms to the theoretical calculation and actual measurement results.

[0083] Further, the shape of the through-hole is a quasi-sector structure, or expansion-reducing holes are opened on both sides of the through-hole. The shape of the expansion-reducing holes is circular or polygonal or special-shaped structure. Corresponding to various RV reducer models, the lateral clearance Δc between the internal cycloid teeth and the cycloid tooth groove on one side is (0.1 - 0.6)λ1.

[0084] Further, the shape of the through-hole is a quasi-sector structure, or expansion-reducing holes are opened on both sides of the through-hole. The shape of the expansion-reducing holes is circular or polygonal or special-shaped structure. Corresponding to various RV reducer models, the lateral clearance Δc between the internal cycloid teeth and the cycloid tooth groove on one side is (0.1 - 4)λ2.

[0085] Further, the shape of the through-hole is a quasi-sector structure, or expansion-reducing holes are opened on both sides of the through-hole. The shape of the expansion-reducing holes is circular or polygonal or special-shaped structure. Corresponding to various RV reducer models, the lateral clearance Δc between the internal cycloid teeth and the cycloid tooth groove on one side is (0.2 - 3)λ2.

[0086] Even further, the shape of the through-hole is a quasi-sector structure, or expansion-reducing holes are opened on both sides of the through-hole. The shape of the expansion-reducing holes is circular or polygonal or special-shaped structure. Corresponding to various RV reducer models, the lateral clearance Δc between the internal cycloid teeth and the cycloid tooth groove on one side is λ2.

[0087] Even further, the shape of the through-hole is a quasi-sector structure, or expansion-reducing holes are opened on both sides of the through-hole. The shape of the expansion-reducing holes is circular or polygonal or special-shaped structure. Corresponding to various RV reducer models, the range of the lateral clearance Δc between the internal cycloid teeth and the cycloid tooth groove on one side is: 0.1λ2 ≤ Δc < 0.7λ2.

[0088] Even further, the shape of the through-hole is a quasi-sector structure, or expansion-reducing holes are opened on both sides of the through-hole. The shape of the expansion-reducing holes is circular or polygonal or special-shaped structure. Corresponding to various RV reducer models, the lateral clearance Δc between the internal cycloid teeth and the cycloid tooth groove on one side is (0.1 - 0.6)λ2.

[0089] Furthermore, the shape of the through hole is a quasi-sector structure, or anti-expansion holes are provided on both sides of the through hole, and the shape of the anti-expansion holes is circular or polygonal or special-shaped structure. Corresponding to various RV reducer models, the lateral clearance Δc between the inner cycloid tooth and the cycloid tooth groove on one side is (0.1 - 4)λ.

[0090] Furthermore, the shape of the through hole is a quasi-sector structure, or anti-expansion holes are provided on both sides of the through hole, and the shape of the anti-expansion holes is circular or polygonal or special-shaped structure. Corresponding to various RV reducer models, the lateral clearance Δc between the inner cycloid tooth and the cycloid tooth groove on one side is (0.2 - 3)λ.

[0091] Still further, the shape of the through hole is a quasi-sector structure, or anti-expansion holes are provided on both sides of the through hole, and the shape of the anti-expansion holes is circular or polygonal or special-shaped structure. The lateral clearance Δc between the inner cycloid tooth and the cycloid tooth groove on one side is λ.

[0092] Still further, the shape of the through hole is a quasi-sector structure, or anti-expansion holes are provided on both sides of the through hole, and the shape of the anti-expansion holes is circular or polygonal or special-shaped structure. The range of the lateral clearance between the inner cycloid tooth and the cycloid tooth groove on one side is: 0.1λ ≤ Δc < 0.7λ.

[0093] Still further, the shape of the through hole is a quasi-sector structure, or anti-expansion holes are provided on both sides of the through hole, and the shape of the anti-expansion holes is circular or polygonal or special-shaped structure. Corresponding to various RV reducer models, the lateral clearance Δc between the inner cycloid tooth and the cycloid tooth groove on one side is (0.1 - 0.6)λ. Specific Embodiment 1

[0095] An internal meshing RV-C type reducer for precision control, the structure of which includes an inner cycloid gear ring 1 and a two-stage reduction component placed therein: the first stage reduction component includes a driving wheel 13, a double gear 8 and a planetary gear 12 on a servo motor, the double gear 8 includes a driven wheel 6 and a sun gear 7, the driven wheel 6 is meshed with the driving wheel 13, the sun gear 7 is meshed with the planetary gear 12, the planetary gear 12 is connected to the shaft extension end of the eccentric shaft 11 of the second stage reduction component, a wire tube is arranged in the inner hole of the double gear 8, and the two sides of the double gear 8 are supported by a first bearing 10 and a second bearing 9 on the right rigid disk 5 and the corresponding position of the robot body respectively; the second stage reduction component includes 2 to 3 evenly distributed eccentric shafts 11, a cycloid wheel, a left rigid disk 16 and a right rigid disk 17. The cycloid wheel comprises a left cycloid wheel 3 and a right cycloid wheel 4. The two eccentric sections of the eccentric shaft 11 are provided with needle bearings for supporting the cycloid wheel. The shaft extensions on both sides of the eccentric section of the eccentric shaft are supported in the peripheral holes of the left and right rigid disks by the first and second tapered roller bearings respectively. The left and right rigid disks are supported in the inner holes on both sides of the inner cycloid gear ring 1 by the main bearings 2 respectively. The flanges evenly distributed on the left rigid disk 16 pass through the corresponding three through holes 17 on the cycloid wheel and are connected to the right rigid disk 5 by screws and positioning pins to form a rigid body. The shape of the three through holes 17 is a fan-shaped structure. The cycloid wheel adopts "equidistant-shifted" shaping. The shaping forms a lateral gap Δc and a radial gap between the inner cycloid teeth and the cycloid wheel tooth grooves. The lateral gap Δc on one side of the inner cycloid teeth and the cycloid wheel tooth grooves is Δc =λ, where: λ is the actual lateral thermal expansion of the cycloid wheels 3 and 4 when the reducer does work under the rated torque.

[0096] At the same time, the size of the lateral clearance Δc is related to factors such as the machining accuracy of the adjacent distance of the hypocycloid gear ring, the machining accuracy of the hypocycloid gear ring diameter, the cycloid wheel pitch deviation and the deviation caused by assembly, and is related to the size of the RV reducer model. If the lateral clearance Δc is too small, interference friction will occur, and if it is too large, vibration will easily occur when the input speed is high.

[0097] It can be seen that the lateral clearance Δc in this embodiment is equal to the actual lateral thermal expansion, that is, Δc=λ, which achieves good gear meshing and avoids interference friction; at the same time, it also greatly reduces the requirements for processing accuracy, thereby greatly reducing the company's investment and production and management costs.

[0098] The internal meshing RV-C type reducer for precision control provided by the present invention has the following advantages compared with the prior art:

[0099] (1) The lateral clearance Δc generated by the "equidistant-shifted" shaping method of the present invention is closely related to the thermal expansion of the cycloid wheel, so it has good dynamic characteristics and does not overheat when operating under rated load.

[0100] (2) The present invention uses conventional manufacturing precision, has a simple process and low cost.

[0101] (3) The external dimensions of the present invention are the same as those of common RV reducers and can be interchanged with them.

[0102] The above are only embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the content of the specification of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. An internal meshing RV-C type reducer for precision control, comprising an inner cycloid gear ring and a two-stage reduction component placed therein: the first stage reduction component comprises a driving wheel, a double gear and a planetary gear on a servo motor, the double gear comprises a driven wheel and a sun gear, the driven wheel meshes with the driving wheel, the sun gear meshes with the planetary gear, the planetary gear is connected to the eccentric shaft extension end of the second stage reduction component, a wire tube is arranged in the inner hole of the double gear, and the two sides of the double gear are supported by a first bearing and a second bearing respectively on the corresponding positions of the right rigid disk and the robot body; the second stage reduction component comprises 2 to 3 evenly distributed eccentric The eccentric shaft comprises a left cycloid wheel, a right cycloid wheel, and a left rigid disk. The two eccentric sections of the eccentric shaft are provided with needle bearings for supporting the cycloid wheel. The shaft extensions on both sides of the eccentric section of the eccentric shaft are supported in the peripheral holes of the left and right rigid disks by tapered roller bearings respectively. The left and right rigid disks are supported in the inner holes on both sides of the inner cycloid gear ring by main bearings respectively. The flanges evenly distributed on the left rigid disk pass through the corresponding through holes on the cycloid wheel and are connected to the right rigid disk by screws and positioning pins to form a rigid body. The cycloid wheel comprises a left cycloid wheel and a right cycloid wheel, and adopts "equidistant-shifted" shaping to form a lateral gap Δc and a radial gap between the inner cycloid teeth and the cycloid tooth grooves. It is characterized in that: (1) Adopt "positive equidistant - positive shift distance" modification to form a lateral clearance Δc and a radial clearance between the epicycloid teeth and the cycloid tooth grooves. 1) When λ1 is the theoretical radial thermal expansion amount of the cycloid gear when the reducer does work: The range of the lateral clearance Δc between the unilateral sides of the epicycloid teeth and the cycloid tooth grooves is: 0.2λ1 ≤ Δc ≤ 0.6λ1; 2) When λ2 is the actual radial thermal expansion amount of the cycloid gear when the reducer does work: The range of the lateral clearance Δc between the unilateral sides of the epicycloid teeth and the cycloid tooth grooves is: 0.1λ2 ≤ Δc < 0.7λ2; 3) When λ is the actual lateral thermal expansion amount of the cycloid gear when the reducer does work: The range of the lateral clearance Δc between the unilateral sides of the epicycloid teeth and the cycloid tooth grooves is: 0.1λ ≤ Δc < 0.7λ; (2) The shape of the through - hole is a sector - like structure, or expansion - reducing holes are opened on both sides of the through - hole, and the shape of the expansion - reducing holes is circular or polygonal.

2. The internal meshing RV-C type reducer for precision control according to claim 1, characterized in that: The theoretical radial thermal expansion amount of the cycloid gear λ1=(d0Δt)αt1, the actual radial thermal expansion amount of the cycloid gear λ2=(d0Δt)αt2, the actual lateral thermal expansion amount of the cycloid gear λ=(d0Δt)αt, where αt1 is the theoretical radial thermal expansion coefficient of the cycloid gear bearing steel, αt2 is the actual radial thermal expansion coefficient of the cycloid gear bearing steel, αt is the actual lateral thermal expansion coefficient of the cycloid gear bearing steel, Δt is the temperature rise of the cycloid gear, d0 is the average diameter of the addendum circle and the dedendum circle of the cycloid gear, αt1=(1.378 - 1.382)·10 - 5 (1 / ℃), the temperature rise Δt = 45℃, and λ1=(d0Δt)αt1 = 0.00062d0.

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