RV-C Reducer for Precision Control

Abstract

The present invention discloses an RV-C type reducer for precision control, which relates to the technical field of robot reducers, including a pinion housing 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 an evenly distributed eccentric shaft, a cycloidal wheel, a pinion, a left rigid disk and a right rigid disk. After the cycloidal wheel is reshaped, the lateral clearance between the pinion and the cycloidal wheel tooth groove is 0.1λ1≤Δc<0.7λ1, where λ1 is the theoretical radial thermal expansion of the cycloidal wheel when doing work under rated torque. The cycloidal wheel reshaped of the present invention satisfies the relationship between the lateral clearance Δc and the thermal expansion of the cycloidal 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 RV-C type reducer for precision 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 technologies for the lateral clearance of cycloidal gears 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 / °C) comes from the data on page 95 of "Research on Thermal Expansion of Precision Parts and Precise Thermal Expansion Coefficient of Materials" (Miao Enming, Hefei University, September 2004), which is measured from the actual thermal expansion amount of solid round bar-shaped bearing steel materials. The actual cycloidal 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 study of the actual measurement of the thermal expansion of the existing structure and different structure cycloidal gear bearing steel materials, it is confirmed that there are significant differences in the thermal expansion coefficients of porous disc-shaped structure bearing steel materials and solid round bar-shaped structure bearing steel materials. Therefore, it will be difficult to meet the design requirements for the implementation of the above existing patented technologies.

[0004] The other is patents such as CN 108869644 A and CN 106641110 A, which do not make a quantitative setting for specifically defining the lateral clearance range of the cycloidal gear. They 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 skilled in the art. Summary of the Invention

[0005] The object of the present invention is to propose a correct relationship between the lateral clearance Δc of the cycloidal gear after modification 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 RV-C type reducer for precision control with good dynamic characteristics.

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

[0007] An RV-C type reducer for precise control, which includes a pin gear housing and a two-stage reduction component placed 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, and 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. The two sides of the double gear are respectively supported on the 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 evenly distributed eccentric shafts, cycloidal gears, pin shafts, a left rigid disk, and a right rigid disk. Eccentric shaft bearings for supporting the cycloidal gears are arranged on the two eccentric sections of the eccentric shaft. The two sides of the eccentric sections are respectively supported in the peripheral holes of the left rigid disk and the right rigid disk by tapered roller bearings. The left rigid disk and the right rigid disk are respectively supported in the inner holes on both sides of the pin gear housing by main bearings. The evenly distributed flanges on the left rigid disk pass through the corresponding through holes on the cycloidal gear and are connected to the right rigid disk with screws and positioning pins to form a rigid body. The cycloidal gear includes a left cycloidal gear and a right cycloidal gear, and is modified by "equal pitch - shifted pitch" to form a lateral clearance Δc and a radial clearance between the pin shaft and the tooth groove of the cycloidal gear.

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

[0009] The range of the lateral clearance Δc between the single side of the pin shaft and the tooth groove of the cycloidal gear is: 0.1λ1 ≤ Δc < 0.7λ1;

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

[0011] The lateral clearance Δc between the single side of the pin shaft and the tooth groove of the cycloidal gear is Δc = (0.1 - 5)λ2;

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

[0013] The lateral clearance Δc between the single side of the pin shaft and the tooth groove of the cycloidal gear is Δc = (0.1 - 5)λ.

[0014] In a preferred embodiment of the present invention, the lateral clearance Δc between the single side of the pin shaft and the tooth groove of the cycloidal gear is Δc = (0.2 - 0.6)λ1.

[0015] In a preferred embodiment of the present invention, the lateral clearance Δc between the single side of the pin shaft and the tooth groove of the cycloidal gear is Δc = (0.1 - 4)λ2.

[0016] In a preferred embodiment of the present invention, the lateral clearance Δc between the single side of the pin shaft and the tooth groove of the cycloidal gear is Δc = (0.2 - 3)λ2.

[0017] In a preferred embodiment of the present invention, the lateral clearance Δc between the single side of the pin shaft and the tooth groove of the cycloidal gear is Δc = λ2.

[0018] In a preferred embodiment of the present invention, the range of the lateral clearance between the pin and the unilateral tooth space of the cycloid gear is: 0.1λ2 ≤ Δc < 0.7λ2.

[0019] In a preferred embodiment of the present invention, the lateral clearance Δc between the pin and the unilateral tooth space of the cycloid gear is (0.2 - 0.6)λ2.

[0020] In a preferred embodiment of the present invention, the lateral clearance Δc between the pin and the unilateral tooth space of the cycloid gear is (0.1 - 4)λ.

[0021] In a preferred embodiment of the present invention, the lateral clearance Δc between the pin and the unilateral tooth space of the cycloid gear is (0.2 - 3)λ.

[0022] In a preferred embodiment of the present invention, the lateral clearance Δc between the pin and the unilateral tooth space of the cycloid gear is λ.

[0023] In a preferred embodiment of the present invention, the range of the lateral clearance between the pin and the unilateral tooth space of the cycloid gear is: 0.1λ ≤ Δc < 0.7λ.

[0024] In a preferred embodiment of the present invention, the lateral clearance Δc between the pin and the unilateral tooth space of the cycloid gear is (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, 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 as follows:

[0028] (1) The lateral clearance Δc generated by the "equal - distance - shift - distance" modification adopted by the present invention is closely related to the thermal expansion amount of the cycloid gear, so it has good dynamic characteristics and does not overheat 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. BRIEF 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 drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also 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 RV-C type reducer for precise control according to the present invention;

[0033] Figure 2 is a schematic structural view of a cycloid gear in an RV-C type reducer for precise control according to the present invention;

[0034] Figure 3 is a schematic structural view of another embodiment of a cycloid gear in an RV-C type reducer for precise control according to the present invention;

[0035] In the figure: 1. Pin tooth housing, 2. Main bearing, 3. Left cycloid gear, 4. Right cycloid gear, 5. Right rigid disc, 6. Driven wheel, 7. Sun gear, 8. Double gear, 9. Second bearing, 10. First bearing, 11. Eccentric shaft, 12. Planet gear, 13. Driving wheel, 14. Tapered roller bearing, 15. Eccentric shaft bearing, 16. Left rigid disc, 17. Pin, 18. Through hole, 19. Anti-expansion hole. DETAILED DESCRIPTION OF THE 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 some embodiments of the present invention, rather than all embodiments. 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] An RV-C type reducer for precise control, which comprises a pin gear housing 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, and the sun gear meshes with the planetary gear. The planetary gear is connected to the extended end of the eccentric shaft 11 of the second-stage reduction component. A through wire tube is arranged in the inner hole of the double gear. The two sides of the double gear are respectively supported on the corresponding positions of the right rigid disk 5 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, cycloidal gears, pin shafts, a left rigid disk, and a right rigid disk. Eccentric shaft bearings for supporting the cycloidal gears are provided on the two eccentric sections of the eccentric shaft. The extended ends on both sides of the eccentric section are respectively supported in the peripheral holes of the left rigid disk and the right rigid disk by tapered roller bearings. The left rigid disk and the right rigid disk are respectively supported in the inner holes on both sides of the pin gear housing by main bearings. The evenly distributed flanges on the left rigid disk pass through the corresponding through holes on the cycloidal gear and are connected to the right rigid disk with screws and positioning pins to form a rigid body. The cycloidal gear includes a left cycloidal gear and a right cycloidal gear, and adopts "equal distance - shift distance" modification. The modification forms a lateral clearance Δc and a radial clearance between the pin shaft and the tooth groove of the cycloidal gear. Among them, during the modification, "positive equal distance - positive shift distance" modification is preferably adopted first, and "negative equal distance - negative shift distance" modification can be selected secondly.

[0039] When λ1 is the theoretical radial thermal expansion amount of the cycloidal gear when the reducer does work:

[0040] The range of the lateral clearance Δc is: 0.1λ1 ≤ Δc < 0.7λ1.

[0041] The shape of the through hole on the cycloidal gear can be a quasi-sector structure, or expansion-reducing holes are opened on both sides of the through hole. The shape of the expansion-reducing hole can be circular, polygonal, or irregular.

[0042] According to the discovery in the theory of thermal expansion that thermal deformation is inseparable from shape factors, through the actual measurement and comparative study of the thermal expansion coefficients of the bearing steel materials of cycloidal gears with different structures, it is found that there are differences in the thermal expansion coefficients of the bearing steel materials of cycloidal gears with different structures. Especially, the change in the structure of the through hole or the structure around the through hole of the cycloidal gear has an impact on the thermal expansion of the cycloidal gear. Therefore, reasonably setting the structure of the cycloidal gear, especially reasonably setting the structure of the through hole or around the through hole, to minimize the thermal expansion amount of the cycloidal gear will be most beneficial to the precision design of the reducer. Through the thermal expansion ratio comparison and research of a large number of cycloidal gears with different structures, on the premise of ensuring the stiffness of the cycloidal gear, the through hole of the cycloidal gear 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, polygonal, or irregular structure.

[0043] Therefore,

[0044] (1)When λ2 is the actual radial thermal expansion of the cycloid gear when the reducer does work:

[0045] The lateral clearance Δc between the pin and the unilateral tooth slot of the cycloid gear is Δc = (0.1 - 5)λ2;

[0046] (2)When λ is the actual lateral thermal expansion of the cycloid gear when the reducer does work:

[0047] The lateral clearance Δc between the pin and the unilateral tooth slot of the cycloid gear is Δc = (0.1 - 5)λ.

[0048] Among them, the actual radial thermal expansion of the cycloid gear can be obtained by measuring the thermal expansion, or can be calculated by measuring the thermal expansion coefficient, that is, λ2 = (d0 Δt) αt2, and 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 can be calculated by measuring the thermal expansion coefficient, that is, λ = (d0 Δt) αt, and 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.

[0049] According to the quasi - harmonic approximation theory in "Introduction to Solid State Physics" (Kittel C [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 of the displacement between atoms and the increase of 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.

[0050] 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 value of the thermal expansion coefficient differ greatly from the actual measured value. The currently used thermal expansion coefficient is still the actual measured value of a round bar with a certain size, which inevitably makes the measured value of the thermal expansion coefficient contain the influence of shape factors.

[0051] According to the retrieval 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 / ℃), which is the measured value of a bearing steel material with a solid round bar structure of a certain size.

[0052] According to the linear expansion coefficient and density table of common materials (Table 12.2-4) in "China Mechanical Design Encyclopedia (Volume 1)", the linear expansion coefficient αt table of materials (Table 1-1-12) in "Mechanical Design Manual (Volume 1)", and the linear expansion coefficient table of common materials (Table 1-1-12) in "Modern Mechanical Design Manual (Volume 1)", it is found that referring to the linear expansion coefficient of chromium steel at 20°C to 100°C is αt = 1.12·10 -5 , which is only 81.12% of the thermal expansion coefficient αt = 1.38·10 -5 (1 / °C) of bearing steel.

[0053] According to the national standard GB / T 36491-2018 "General Technical Conditions for Cycloid Pinwheel Planetary Gear Transmission Devices for Robots", the maximum temperature of the reducer housing should not be greater than 60°C, and the operating environmental conditions are -10°C to 40°C. The specific value of the temperature rise of the cycloid wheel can be deduced from the temperature difference between the reducer housing and the environment and the temperature difference between the housing and the cycloid wheel, or it can be directly taken as 45°C. When the temperature rise of the cycloid wheel is taken as 45°C, since the reducer generally operates in a room temperature environment, the corresponding thermal expansion amount of the cycloid wheel set is also relatively high.

[0054] The actual structure of the cycloid wheel is a porous disc-shaped structure, which is very different from the solid round bar-shaped 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.

[0055] Using the relevant thermal expansion research theory, through the actual measurement research on the thermal expansion coefficients of the bearing steel materials of the existing structure and different structures of the cycloid wheel, it is also confirmed that the actual thermal expansion coefficients of the bearing steel materials of the existing structure and different structures of the cycloid wheel are lower than the theoretical thermal expansion coefficient of the bearing steel material.

[0056] To sum up, the theoretical thermal expansion amount, its 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. To obtain the correct lateral clearance, the actual thermal expansion amount, or the data of the thermal expansion coefficient and temperature rise of the cycloid wheel can be measured by various existing means, and the actual required lateral clearance Δc parameters can be obtained by multiplying the thermal expansion amount by a certain coefficient for adjustment.

[0057] Even if the amount of thermal expansion, coefficient of thermal expansion, temperature, and the coefficient multiplied by those of an ordinary technician in the art are different from those of this patent, as long as the final value of the lateral clearance Δc falls within the scope of the claims of this patent, it is still included in the scope of this patent 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 since 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 already included in the patent protection scope of this invention.

[0058] In some of the prior arts, due to reasons such as the relatively large values taken for the theoretical coefficient of thermal expansion, temperature rise, and adjustment coefficient, the value of the lateral clearance Δc is too large, resulting in poor accuracy.

[0059] In some of the prior arts, due to the too small value of the lateral clearance Δc, the cycloid gear and the pin engage with interference, inevitably resulting in 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 Co., Ltd. as an example. The parameters publicly released 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'.

[0060] When the backlash = 0.29' remains unchanged, through calculation, it is known that:

[0061] The lateral clearance ΔC = 0.003 (mm).

[0062] 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 coefficient of thermal expansion 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.

[0063] 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.

[0064] 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. In the formula, λ is the actual lateral thermal expansion amount of the cycloid gear when the reducer does work under the rated torque.

[0065] 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.

[0066] Therefore, it is obtained 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.

[0067] It can be seen from this 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 an interference fit and friction between the cycloid gear and the pin, and problems such as heat generation, wear, and decreased accuracy, which are poor dynamic performance, will inevitably occur.

[0068] The usage effects of the reducer with different lateral clearances are shown in the following table.

[0069]

[0070] As can be seen from the above table:

[0071] Performance 1: When the lateral clearance Δc satisfies 0.1λ1 ≤ Δc < 0.7λ1, it meets the standard;

[0072] Performance 2: When the lateral clearance Δc = (0.1 - 5)λ2, it meets the standard;

[0073] Performance 3: When the lateral clearance Δc = (0.7 - 5)λ1 and Δc < 0.1λ1, Δc > 5λ1, it does not meet the standard;

[0074] Performance 4: When the lateral clearance Δc < 0.1λ2 and Δc > 5λ2, it does not meet the standard;

[0075] Performance 5: Under the condition of meeting the standard, the temperature rise is lower than 45°C.

[0076] 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:

[0077] (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;

[0078] (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.

[0079] (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.

[0080] 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 pin and the tooth groove of the cycloid gear 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.

[0081] 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 pin and the tooth groove of the cycloid gear on one side is (0.2 - 0.6)λ1.

[0082] 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 pin and the tooth groove of the cycloid gear on one side is (0.1 - 4)λ2.

[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 pin and the tooth groove of the cycloid gear on one side is (0.2 - 3)λ2.

[0084] 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 pin and the tooth groove of the cycloid gear on one side is λ2.

[0085] 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 pin and the tooth groove of the cycloid gear on one side is: 0.1λ2 ≤ Δc < 0.7λ2.

[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 pin and the tooth groove of the cycloid gear on one side is (0.2 - 0.6)λ2.

[0087] 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. 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 pin and the unilateral tooth space of the cycloid gear is (0.2 - 4)λ.

[0088] 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. 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 pin and the unilateral tooth space of the cycloid gear is (0.2 - 3)λ.

[0089] 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. 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 pin and the unilateral tooth space of the cycloid gear is λ.

[0090] 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. The shape of the anti-expansion holes is circular or polygonal or special-shaped structure. Corresponding to various RV reducer models, the range of the lateral clearance between the pin and the unilateral tooth space of the cycloid gear is: 0.1λ ≤ Δc < 0.7λ.

[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. 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 pin and the unilateral tooth space of the cycloid gear is (0.2 - 0.6)λ. Specific Embodiment 1

[0093] An RV-C type reducer for precise control, the structure of which includes a pin gear housing 1 and a two-stage reduction component disposed therein: The first-stage reduction component includes a driving wheel 13 on a servo motor, a double gear 8 and a planetary gear 12. The double gear 8 includes a driven wheel 6 and a sun gear 7. The driven wheel 6 meshes with the driving wheel 13, and the sun gear 7 meshes with the planetary gear 12. The planetary gear 12 is connected to the shaft extension end of an eccentric shaft 11 of the second-stage reduction component. A through wire tube is provided in the inner hole of the double gear 8. Both sides of the double gear 8 are respectively supported on the right rigid disk 5 and corresponding positions of the robot body by a first bearing 10 and a second bearing 9. The second-stage reduction component includes 2 to 3 evenly distributed eccentric shafts 11, cycloidal gears, pin shafts 17, a left rigid disk 16 and a right rigid disk 5. Eccentric shaft bearings 15 for supporting the cycloidal gears are provided on two eccentric sections of the eccentric shaft 11. The shaft extensions on both sides of the eccentric sections are respectively supported in peripheral holes of the left rigid disk 16 and the right rigid disk 5 by tapered roller bearings 14. The left rigid disk 16 and the right rigid disk 5 are respectively supported on inner holes on both sides of the pin gear housing 1 by main bearings 2. Three evenly distributed flanges on the left rigid disk 16 pass through corresponding three through holes on the cycloidal gear and are connected to the right rigid disk 5 with screws and positioning pins to form a rigid body. The shape of the three through holes 18 is a quasi-sector structure.

[0094] The cycloidal gear includes a left cycloidal gear 3 and a right cycloidal gear 4. The cycloidal gear adopts "equidistant-shift" modification, and the modification forms a lateral clearance Δc and a radial clearance between the pin shaft 17 and the tooth grooves of the cycloidal gears 3 and 4. The unilateral lateral clearance Δc between the pin shaft 4 and the tooth grooves of the cycloidal gears 3 and 4 is λ, where: λ is the actual lateral thermal expansion amount of the cycloidal gears 3 and 4 when the reducer does work under the rated torque.

[0095] 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 pin shaft, the machining accuracy of the pin shaft diameter, the fit clearance between the pin shaft and the semi-embedded hole, the tooth pitch deviation of the cycloidal gear, and the deviation generated during assembly. It is related to the model size of the RV reducer. If the lateral clearance Δc is too small, interference friction will occur. If it is too large, vibration is likely to occur when the input speed is on the high side.

[0096] From this, it can be known that the lateral clearance Δc in this embodiment is equal to the actual lateral thermal expansion amount, that is, Δc = λ, achieving good gear meshing and avoiding interference friction; at the same time, it also greatly reduces the requirements for machining accuracy, thereby greatly reducing the investment, production and management costs of enterprises.

[0097] The RV-C type reducer for precise control provided by the present invention has the following advantages compared with the prior art:

[0098] (1) The lateral clearance Δc generated by the "equidistant-shift" modification adopted by the present invention is closely related to the thermal expansion amount of the cycloidal gear, so it has good dynamic characteristics and does not overheat when operating and doing work under the rated load.

[0099] (2) The present invention uses conventional manufacturing precision, has a simple process and low cost.

[0100] (3) The external dimensions of the present invention are the same as those of common RV reducers and can be interchanged with them.

[0101] The above are only embodiments of the present invention and do not limit the patent scope of the present invention accordingly. 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 RV-C type reducer for precise control, comprising a pin gear housing 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, and 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 provided in the inner hole of the double gear. The two 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. The second-stage reduction component includes evenly distributed eccentric shafts, cycloidal gears, pin shafts, a left rigid disk, and a right rigid disk. Eccentric shaft bearings for supporting the cycloidal gears are provided on the two eccentric segments of the eccentric shaft. The two shaft extensions on both sides of the eccentric segment are respectively supported in the peripheral holes of the left rigid disk and the right rigid disk by tapered roller bearings. The left rigid disk and the right rigid disk are respectively supported in the inner holes on both sides of the pin gear housing by main bearings. The evenly distributed flanges on the left rigid disk pass through the corresponding through holes on the cycloidal gear and are connected to the right rigid disk with screws and positioning pins to form a rigid body. The cycloidal gear includes a left cycloidal gear and a right cycloidal gear, and is modified by "equidistant - shift distance" so that a lateral clearance Δc and a radial clearance are formed between the pin shaft and the tooth slot of the cycloidal gear. It is characterized in that: (1) Adopt "positive equidistant - positive shift distance" modification, which forms a lateral clearance Δc and a radial clearance between the pin and the cycloid gear tooth groove; 1) When λ1 is the theoretical radial thermal expansion of the cycloid gear when the reducer does work: The range of the lateral clearance Δc between the pin and the unilateral cycloid gear tooth groove is: 0.2λ1 ≤ Δc < 0.6λ1; 2) When λ2 is the actual radial thermal expansion of the cycloid gear when the reducer does work: The range of the lateral clearance Δc between the pin and the unilateral cycloid gear tooth groove is: 0.1λ2 ≤ Δc < 0.7λ2; 3) When λ is the actual lateral thermal expansion of the cycloid gear when the reducer does work: The range of the lateral clearance Δc between the pin and the unilateral cycloid gear tooth groove is: 0.1λ ≤ Δc < 0.7λ; (2) The shape of the through - hole is a quasi - sector 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 RV-C type reducer for precise control according to claim 1, characterized in that: The theoretical radial thermal expansion of the cycloid gear λ1 = (d0 Δt) αt1, the actual radial thermal expansion of the cycloid gear is λ2 = (d0 Δt) αt2, and the actual lateral thermal expansion of the cycloid gear is λ = (d0 Δt) 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, and αt1 = (1.378 - 1.382)·10 -5 (-6) (1 / ℃), the temperature rise Δt = 45℃, and λ1 = (d0 Δt) αt1 = 0.00062d0.

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