RV Reducer for Precision Control

Abstract

The present invention discloses an RV reducer for precision control, which relates to the technical field of robot reducers. It includes a pin tooth housing and a two-stage reduction component disposed therein. The first-stage component includes an input shaft, a sun gear, and planet gears. The second-stage component includes an eccentric shaft, a cycloid gear, a pin, a rigid disk, and a bearing. After the cycloid gear is modified, the lateral clearance Δc between the pin and both sides of the tooth groove of the cycloid gear satisfies 0.1λ1 ≤ Δc < 0.7λ1, where λ1 is the theoretical radial thermal expansion amount of the cycloid gear when doing work under the rated torque. The cycloid gear modification of the present invention satisfies the relationship between the lateral clearance Δc and the thermal expansion amount λ1 of the cycloid gear, thus having good dynamic characteristics, less heat generation, and less wear. It has conventional manufacturing accuracy and 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 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 localized.

[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) and is measured from the actual thermal expansion amount of the solid round bar-shaped structure bearing steel material. However, 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 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, which do not make a quantitative setting for specifically defining the lateral clearance range of the cycloidal 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. Such 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 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 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 RV reducer for precise control, which includes a pin gear housing and a two-stage reduction component disposed therein:

[0008] The first-stage reduction component includes an input shaft, a sun gear, and two or three evenly distributed planet gears;

[0009] The second-stage reduction component includes an eccentric shaft, a cycloid gear, a pin, a rigid disk, and a bearing; two or three eccentric shafts are evenly distributed around the input shaft, the shaft extension end of the eccentric shaft is connected to the planet gear, and the first bearing for supporting the cycloid gear is provided on two eccentric segments of the eccentric shaft. The 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 the second bearing, and 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 the third bearing; the input shaft is respectively supported in the central holes of the left rigid disk and the right rigid disk by the fourth bearing, and two or three flanges are evenly distributed on the left rigid disk, passing through two or three through holes evenly distributed on the cycloid gear, and are connected to the right rigid disk with screws and positioning pins to form a rigid body; the cycloid gear includes a left cycloid gear and a right cycloid gear, and adopts "equidistant - shift" modification, and the modification forms a lateral clearance Δc and a radial clearance between the pin and the tooth groove of the cycloid gear.

[0010] (1) When λ1 is the theoretical radial thermal expansion amount of the cycloid gear when the reducer does work:

[0011] The range of the lateral clearance Δc between the pin and the tooth groove of the cycloid gear on one side is: 0.1λ1 ≤ Δc < 0.7λ1;

[0012] (2) When λ2 is the actual radial thermal expansion amount of the cycloid gear when the reducer does work:

[0013] The lateral clearance Δc between the pin and the tooth groove of the cycloid gear on one side is Δc = (0.1 - 5)λ2;

[0014] (3) When λ is the actual lateral thermal expansion amount of the cycloid gear when the reducer does work:

[0015] The lateral clearance Δc between the pin and the tooth groove of the cycloid gear on one side is Δc = (0.1 - 5)λ.

[0016] In a preferred embodiment of the present invention, the lateral clearance Δc between the pin and the tooth groove of the cycloid gear on one side is Δc = (0.2 - 0.6)λ1.

[0017] In a preferred embodiment of the present invention, the lateral clearance Δc between the pin and the tooth groove of the cycloid gear on one side is Δc = (0.1 - 4)λ2.

[0018] In a preferred embodiment of the present invention, the lateral clearance Δc between the pin and the tooth groove of the cycloid gear on one side is Δc = (0.2 - 3)λ2.

[0019] In a preferred embodiment of the present invention, the lateral clearance Δc between the pin and the tooth groove of the cycloid gear on one side is Δc = λ2.

[0020] 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.

[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 - 0.6)λ2.

[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 (0.1 - 4)λ.

[0023] 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.

[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 λ.

[0025] 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.

[0026] 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.

[0027] In a preferred embodiment of the present invention, 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 or irregular.

[0028] In a preferred embodiment of the present invention, the theoretical radial thermal expansion amount λ1 of the cycloid gear = (d0 Δt) αt1, the actual radial thermal expansion amount λ2 of the cycloid gear = (d0 Δt) αt2, and the actual lateral thermal expansion amount λ of the cycloid gear = (d0 Δt) αt, where αt, αt1, and αt2 are respectively the actual lateral thermal expansion coefficient, theoretical radial thermal expansion coefficient, and actual radial 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 = 1.38·10 -5 (1 / °C), the temperature rise Δt = 45°C, and λ1 = (d0 Δt) αt = 0.00062d0.

[0029] The beneficial effects of the present invention are:

[0030] (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 amount of the cycloid gear, so it has good dynamic characteristics and does not overheat when operating under rated load.

[0031] (2) The present invention adopts conventional manufacturing precision, with simple process and low cost;

[0032] (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

[0033] 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 also be obtained based on these drawings, where:

[0034] Figure 1 is a schematic cross-sectional view of the structure of a preferred embodiment of an RV reducer for precise control according to the present invention;

[0035] Figure 2 is a schematic structural view of a cycloid gear in an RV reducer for precise control according to the present invention;

[0036] Figure 3 is a schematic structural view of another embodiment of a cycloid gear in an RV reducer for precise control according to the present invention;

[0037] In the figure: 1. Pin tooth housing, 2. Third bearing, 3. Left cycloid gear, 4. Pin, 5. Right cycloid gear, 6. Eccentric shaft, 7. Second bearing, 8. First bearing, 9. Input shaft, 10. Fourth bearing, 11. Flange, 12. Right rigid disk, 13. Left rigid disk, 14. Sun gear, 15. Planet gear, 16. Through hole, 17. Anti-expansion hole. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some 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.

[0039] Please refer to Figures 1 - 3 , the embodiments of the present invention include:

[0040] An RV reducer for precise control, which includes a pin tooth housing and a two-stage reduction component disposed therein:

[0041] The first-stage reduction component includes an input shaft, a sun gear, and 2 or 3 evenly distributed planet gears;

[0042] The second-stage deceleration component includes an eccentric shaft, a cycloid gear, a pin, a rigid disc, and a bearing; 2 or 3 of the eccentric shafts are evenly distributed around the input shaft. The extended end of the eccentric shaft is connected to a planetary gear. The first bearing for supporting the cycloid gear is provided on 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 disc and the right rigid disc by the second bearing. The left rigid disc and the right rigid disc are respectively supported in the inner holes on both sides of the pin tooth housing by the third bearing; the input shaft is respectively supported in the central holes of the left rigid disc and the right rigid disc by the fourth bearing. 2 or 3 flanges are evenly distributed on the left rigid disc, passing through 2 or 3 through holes evenly distributed on the cycloid gear, and are connected to the right rigid disc with screws and positioning pins to form a rigid body; the cycloid gear includes a left cycloid gear and a right cycloid gear, and adopts "equal-distance - shift-distance" modification. The modification forms a lateral clearance Δc and a radial clearance between the pin and the tooth groove of the cycloid 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.

[0043] When λ1 is the theoretical radial thermal expansion amount of the cycloid gear when the speed reducer does work:

[0044] The range of the lateral clearance Δc is: 0.1λ1 ≤ Δc < 0.7λ1.

[0045] The shape of the through hole on the cycloid 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 special-shaped.

[0046] 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 bearing steel materials of cycloid gears with different structures, it is found that there are differences in the thermal expansion coefficients of bearing steel materials of cycloid gears with different structures. In particular, the change in the through hole structure or the structure around the through hole of the cycloid gear has an impact on the thermal expansion of the cycloid gear. Therefore, reasonably setting the structure of the cycloid gear, especially reasonably setting the structure of the through hole or around the through hole, to minimize the thermal expansion amount of the cycloid gear will be most beneficial to the precision design of the speed reducer. Through a large number of thermal expansion ratio comparison studies of cycloid gears with different structures, on the premise of ensuring the stiffness of the cycloid gear, the through hole of the cycloid gear is set from the existing circular or sector structure to a quasi-sector shape, that is, the through hole is expanded to both sides of the sector 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 special-shaped structure.

[0047] Therefore,

[0048] (1) When λ2 is the actual radial thermal expansion amount of the cycloid gear when the speed reducer does work:

[0049] The lateral clearance Δc between the pin and the tooth groove of the cycloid gear on one side = (0.1 - 5)λ2;

[0050] (2) When λ is the actual lateral thermal expansion amount of the cycloid gear when the speed reducer does work:

[0051] The lateral clearance Δc between the pin and the unilateral tooth space of the cycloid gear is Δc = (0.1 - 5)λ.

[0052] 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.

[0053] 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 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.

[0054] 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 the thermal expansion coefficient usually has simple calculation methods, statistical calculation methods, and Grüneisen formula, 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.

[0055] According to the information retrieved 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 αt of the bearing steel = 1.38·10 -5 (1 / ℃), which is the measured value of the bearing steel material with a solid round bar structure of a certain size.

[0056] 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 Handbook (Volume 1)", and the linear expansion coefficient table of common materials (Table 1-1-12) in "Modern Mechanical Design Handbook (Volume 1)", it is retrieved that, referring to the fact that the linear expansion coefficient of chromium steel 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.

[0057] 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 gear can be calculated by the temperature difference between the reducer housing and the environment and the temperature difference between the housing and the cycloid gear, or it can be directly taken as 45°C. When the temperature rise of the cycloid gear is taken as 45°C, since the reducer generally operates in a room temperature environment, the corresponding thermal expansion amount of the set cycloid gear is also relatively high.

[0058] The actual structure of the cycloid gear 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 gear will be lower than the theoretical thermal expansion coefficient of the bearing steel material.

[0059] 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 gear, 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 gear are lower than the theoretical thermal expansion coefficient of the bearing steel material.

[0060] In summary, the theoretical thermal expansion amount, its thermal expansion coefficient, and temperature rise of the cycloid gear 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 gear 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.

[0061] Although 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 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.

[0062] 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.

[0063] In some of the prior arts, due to the too small value of the lateral clearance Δc, the involute gear and the pin are in interference friction, 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'.

[0064] When the backlash = 0.29' remains unchanged, through calculation, it is known that:

[0065] The lateral clearance ΔC = 0.003 (mm).

[0066] And the theoretical radial thermal expansion amount of the involute gear λ1=(d0Δt) αt = 0.00062 d0 (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 involute gear.

[0067] Furthermore, through calculation, it is obtained that the actual radial thermal expansion amount λ2 of the involute gear is less than the theoretical radial thermal expansion amount λ1, that is, λ2<λ1.

[0068] Furthermore, through calculation, it is obtained that the actual radial thermal expansion amount λ2 of the involute 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 involute gear when the reducer does work under the rated torque.

[0069] At the same time, it is obtained that the actual lateral thermal expansion amount λ of the involute gear is less than the theoretical radial thermal expansion amount λ1, that is, λ<λ1.

[0070] 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.

[0071] From this, it is 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 an interference fit and friction between the cycloid gear and the pin, and problems such as heat generation, wear, and reduced accuracy in dynamic performance will inevitably occur.

[0072] The usage effects of the reducer at different lateral clearances are shown in the following table.

[0073]

[0074] As can be seen from the above table:

[0075] Performance 1: When the lateral clearance Δc satisfies 0.1λ1 ≤ Δc < 0.7λ1, it meets the standard;

[0076] Performance 2: When the lateral clearance Δc = (0.1 - 5)λ2, it meets the standard;

[0077] Performance 3: When the lateral clearance Δc = (0.7 - 5)λ1 and Δc < 0.1λ1, Δc > 5λ1, it does not meet the standard;

[0078] Performance 4: When the lateral clearance Δc < 0.1λ2 and Δc > 5λ2, it does not meet the standard;

[0079] Performance 5: Under the condition of meeting the standard, the temperature rise is lower than 45°C.

[0080] 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:

[0081] (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;

[0082] (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.

[0083] (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.

[0084] 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.

[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, and 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.

[0086] 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, and 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.

[0087] 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, and 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.

[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, and 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.

[0089] 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, and 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.

[0090] 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, and 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.

[0091] Furthermore, the shape of the through-hole is a fan-like 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 tooth groove of the cycloid gear on one side is (0.1-4)λ.

[0092] Furthermore, the shape of the through-hole is a fan-like 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 tooth groove of the cycloid gear on one side is (0.2-3)λ.

[0093] Still further, the shape of the through-hole is a fan-like 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 tooth groove of the cycloid gear on one side is λ.

[0094] Still further, the shape of the through-hole is a fan-like 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 tooth groove of the cycloid gear on one side is: 0.1λ ≤ Δc < 0.7λ.

[0095] Still further, the shape of the through-hole is a fan-like 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 tooth groove of the cycloid gear on one side is (0.2-0.6)λ. Specific Embodiment 1

[0097] An RV reducer for precise control, whose structure includes a pin gear housing 1 and a two-stage reduction component disposed therein: the first-stage reduction component includes an input shaft 9, a sun gear 14, and three evenly distributed planet gears 15; the second-stage reduction component includes an eccentric shaft 6, a left cycloid gear 3 and a right cycloid gear 5, a pin 4, a left rigid disk 13 and a right rigid disk 12, and bearings. The three eccentric shafts 6 are evenly distributed around the input shaft 9. The shaft extension end of the eccentric shaft 6 is connected to the planet gear 15. The first bearings 8 for supporting the cycloid gears are provided on two eccentric segments of the eccentric shaft 6. The shaft extensions on both sides of the eccentric segments are respectively supported in the peripheral holes of the left rigid disk 13 and the right rigid disk 12 by the second bearings 7. The left rigid disk 13 and the right rigid disk 12 are respectively supported in the inner holes on both sides of the pin gear housing 1 by the third bearings 2. The input shaft 9 is respectively supported in the central holes of the left rigid disk 13 and the right rigid disk 12 by the fourth bearings 10. The three flanges 11 evenly distributed on the left rigid disk 13 pass through the corresponding three through holes 16 on the cycloid gear and are connected to the right rigid disk 12 with screws and positioning pins to form a rigid body. The shape of the three through holes 16 is a quasi-sector structure. The cycloid gears 3 and 5 adopt "equal pitch - shifted pitch" modification, and the modification forms a lateral clearance Δc and a radial clearance between the pin 4 and the tooth grooves of the cycloid gears 3 and 5. The lateral clearance Δc on one side between the pin 4 and the tooth grooves of the cycloid gears 3 and 5 is Δc = λ, where: λ is the actual lateral thermal expansion amount of the cycloid gears 3 and 5 when the reducer does work under the rated torque.

[0098] 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 pins, the machining accuracy of the pin diameter, the fit clearance between the pin and the semi-buried hole, the tooth pitch deviation of the cycloid 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.

[0099] 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, which realizes good gear meshing and avoids 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.

[0100] The RV reducer for precise control provided by the present invention has the following advantages compared with the prior art:

[0101] (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 amount λ of the cycloid gear, so it has good dynamic characteristics and does not overheat when operating and doing work under the rated load.

[0102] (2) The present invention uses conventional manufacturing accuracy, has a simple process, and low cost.

[0103] (3) The external dimensions of the present invention are the same as those of the commonly used RV reducer and can be interchanged with it.

[0104] The above are only embodiments of the present invention, and thus 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 similarly be included within the patent protection scope of the present invention.

Claims

1. An RV reducer for precision control, comprising a pin gear housing and a two-stage reduction component disposed therein: The first-stage reduction component includes an input shaft, a sun gear and a planetary gear; The second-stage reduction component includes an eccentric shaft, a cycloid gear, a pin, a rigid disk, and a bearing. The eccentric shafts are evenly distributed around the input shaft. The extended end of the eccentric shaft is connected to the planetary gear. The first bearings for supporting the cycloid gear are provided on two eccentric segments of the eccentric shaft. The extended ends 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 the second 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 the third bearings. The input shaft is respectively supported in the central holes of the left rigid disk and the right rigid disk by the fourth bearings. The left rigid disk is evenly provided with flanges, which pass through the evenly distributed through holes on the cycloid gear and are connected to the right rigid disk with screws and positioning pins to form a rigid body. The cycloid gear includes a left cycloid gear and a right cycloid gear. The "equidistant - shift" modification is adopted to form a lateral clearance Δc and a radial clearance between the pin and the tooth groove of the cycloid gear. It is characterized in that: (1)The "positive equal-distance - positive shift-distance" modification is adopted to form 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 amount of the cycloid gear when the reducer does work: The range of the lateral clearance Δc between the pin and the cycloid gear tooth groove on one side 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 pin and the cycloid gear tooth groove on one side 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 pin and the cycloid gear tooth groove on one side is: 0.1λ ≤ Δc < 0.7λ; (2)The through hole of the cycloid gear 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.

2. The RV reducer for precision control according to claim 1, characterized in that: The theoretical radial thermal expansion amount of the cycloid gear λ1 = (d0 Δt) α t1 , the actual radial thermal expansion of the cycloid gear λ2 = (d0Δt) α t2 , the actual lateral thermal expansion of the cycloid gear λ = (d0 Δt) α t , where, α t1 is the theoretical radial thermal expansion coefficient of the cycloid gear bearing steel, α t2 is the actual radial thermal expansion coefficient of the cycloid gear bearing steel, α t 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, α t1 = (1.378~1.382)·10 -5 (1 / °C), the temperature rise Δt = 45°C, λ1 = (d0Δt) α t1 = 0.00062d0.

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