A zero-backlash harmonic reducer and calculation method

Abstract

The present invention provides a zero-backlash harmonic reducer, which includes a rigid gear, a flexible gear installed inside the rigid gear, and a double semi-circular wave generator assembly disposed inside the flexible gear; the left end of the flexible gear has external teeth; the rigid gear has internal teeth that cooperate with the external teeth; the cross-section of the external teeth is semi-circular arc-shaped; the radius of the external teeth gradually decreases from left to right, forming conical external teeth, and the radius of the leftmost external tooth circle is R 42 , and the radius of the rightmost external tooth circle is R 41 ; the double semi-circular wave generator assembly includes a double semi-circular cam and a flexible bearing installed between the double semi-circular cam and the flexible gear; it shows that the transmission accuracy of the present invention is higher than that of conventional harmonic reducers.

Description

Technical Field

[0001] The present invention relates to the technical field of harmonic reducers, and particularly relates to a zero-backlash harmonic reducer. Background Art

[0002] A harmonic reducer mainly consists of four basic components: a wave generator, a flexible gear, a flexible bearing, and a rigid gear. A harmonic drive reducer is a gear drive that relies on a wave generator equipped with a flexible bearing to cause the flexible gear to generate controllable elastic deformation and mesh with the rigid gear to transmit motion and power. Applied disciplines: Mechanical Engineering (first-level discipline); Transmission (second-level discipline); Gear Transmission (third-level discipline). The harmonic gear drive reducer is a new type of reducer developed based on the principle of planetary gear drive. Harmonic gear drive (abbreviation: harmonic drive).

[0003] Currently, all harmonic reducers use straight-tooth transmission. A number of straight teeth are distributed on the outer circumference of the flexible gear, and straight teeth that cooperate with the outer teeth of the flexible gear are distributed on the inner circumference of the rigid gear. When using straight-tooth transmission, first, the machining accuracy requirements for the teeth are very high; otherwise, it is easy to affect the transmission accuracy. In addition, due to the deformation of the flexible gear, the deformation amounts at different positions of the outer teeth of the flexible gear cannot reach consistency. The meshing degree between two straight teeth is not high enough, and the backlash is also relatively large, thus affecting the transmission accuracy. Summary of the Invention

[0004] The purpose of the present invention is to provide a zero-backlash harmonic reducer to solve the problems mentioned in the background art.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A zero-backlash harmonic reducer includes a rigid gear, a flexible gear installed inside the rigid gear, and a double semi-circular wave generator assembly disposed inside the flexible gear; the left end of the flexible gear has outer teeth; the rigid gear has inner teeth that cooperate with the outer teeth; the cross-section of the outer teeth is semi-circular arc-shaped; the radius of the outer teeth gradually decreases from left to right, forming conical outer teeth, and the radius of the outermost left outer tooth circle is R 42 , and the radius of the outermost right outer tooth circle is R 41 ; the double semi-circular wave generator assembly includes a double semi-circular cam and a flexible bearing installed between the double semi-circular cam and the flexible gear.

[0007] For a further description of the present invention, the right ends of the flexible gear and the rigid gear are connected by a crossed roller bearing; the crossed roller bearing includes an inner ring of the roller bearing, an outer ring of the roller bearing, and rollers; the inner ring of the roller bearing is fixed to the left end of the flexible gear; the outer ring of the roller bearing is fixed to the left end of the rigid gear; the rollers are arranged crosswise between the inner ring of the roller bearing and the outer ring of the roller bearing; a gasket is further provided between the inner ring of the roller bearing and the flexible gear.

[0008] For further description of the present invention, the number of internal teeth of the rigid gear is two more than the number of external teeth of the flexible gear.

[0009] For further description of the present invention, the cone angle A of the external teeth is greater than 0° and less than 3°.

[0010] For further description of the present invention, the length of the external teeth of the flexible gear is 1 - 1.5 times the width of the flexible bearing.

[0011] A method for calculating the size and tooth profile of a bevel gear harmonic reducer, comprising the following steps:

[0012] 1) First, determine the length of the semi-major axis R7 after the deformation of the flexible gear; the wall thickness h1 of the flexible gear; the difference between the inner and outer radii h2 of the flexible bearing; the width W1 of the flexible bearing; the number of teeth of the flexible gear Z2 = n; the module at the distribution circle of the external teeth of the flexible gear is m; the external tooth circle radius R at the leftmost end of the external teeth of the flexible gear 42 , the external tooth circle radius R at the rightmost end of the external teeth of the flexible gear 41 ;

[0013] 2) According to the formula, calculate the external tooth distribution circle radius R6 = Z2 * m / 2 of the flexible gear in the original state, the tooth pitch P at the distribution circle of the external teeth of the flexible gear = mπ, and the length L1 of the external teeth of the flexible gear = 1 - 1.5 times W1, then the specification size of the flexible gear can be obtained;

[0014] 3) Calculate the distribution circle radius R5 of the external teeth of the flexible gear on the double semi-circles after deformation through the formula R5 = (πR6 - 2R7) / (π - 2), and the eccentricity R1 of the double semi-circles after the deformation of the flexible gear = π(R7 - R6) / (π - 2);

[0015] 4) Calculate the double semi-circle radius R8 of the double semi-circle wave generator assembly = R5 - h1; the double semi-circle eccentricity R2 of the double semi-circle wave generator assembly = R1;

[0016] 5) Calculate the double semi-circle radius R9 of the double semi-circle cam = R8 - h2; the double semi-circle eccentricity R3 of the double semi-circle cam = R2; then the specification size of the double semi-circle generator assembly can be obtained;

[0017] 6) Determine the number of internal teeth of the rigid gear Z1 = Z2 + 2;

[0018] 7) Calculate the motion law of the flexible gear. When the wave generator rotates clockwise by an angle ω, the flexible gear rotates counterclockwise by an angle ω1 = ω(Z1 - Z2) / Z2 = 2ω / Z2;

[0019] 8) With the circular arc at the tip of the rigid gear teeth as the reference, design the enveloping tooth profile of the rigid gear according to the motion law of the flexible gear and the tooth profile of the external teeth of the flexible gear. Calculate the primary enveloping trajectory of the tooth profile in the tip region of the flexible gear in the root region of the rigid gear, and calculate the secondary enveloping trajectory of the tooth profile in the root region of the flexible gear in the tip region of the rigid gear. Together, they form the complete tooth profile of the rigid gear, forming a conical internal tooth that matches the conical external teeth of the flexible gear.

[0020] Further, in step (3), the length L1 of the external teeth of the flexible gear is 1.2W1.

[0021] The beneficial effects of the present invention are:

[0022] In this design, by setting the external teeth of the flexible gear as conical teeth and the cross-section as a semi-circular structure, the internal teeth of the rigid gear match the external teeth of the flexible gear, which is also a conical structure. This setting can improve the meshing degree with the rigid gear, and the semi-circular cross-section structure can also improve the smoothness when the external teeth and internal teeth move relative to each other, without the phenomenon of gear jamming. Due to the design of the conical teeth, this design can adjust the left and right positions of the flexible gear by using gaskets to improve the matching degree between the flexible gear and the rigid gear, so that the machining accuracy requirements for the flexible gear and the rigid gear do not need to be too high, and a high-precision meshing effect can be achieved, realizing zero backlash meshing transmission. Therefore, the transmission accuracy of this scheme is higher than that of the conventional harmonic reducer and is suitable for mechanical engineering with high requirements for transmission accuracy. Description of the Drawings

[0023] Figure 1 is the overall structure diagram of the semi-sectional structure of the present invention;

[0024] Figure 2 is Figure 1 the sectional view taken along A-A in

[0025] Figure 3 is Figure 2 the structure diagram of the double semi-circular wave generator assembly and the flexible gear in

[0026] Figure 4 is Figure 3 the sectional view of the external teeth of the flexible gear along B-B in

[0027] Figure 5 is Figure 2 the structure diagram of the double semi-circular wave generator assembly in

[0028] Figure 6 is Figure 2 the structure diagram of the double semi-circular cam in

[0029] Figure 7 is the schematic diagram of the distribution circle distribution trajectory of the external teeth of the flexible gear of the present invention;

[0030] Figure 8It is a schematic diagram of the distribution locus of the outer teeth of the flexspline after it is supported by the present invention;

[0031] Figure 9 It is Figure 1 the structural diagram of the flexspline in Specific embodiments

[0032] The present invention will be further described below with reference to the accompanying drawings:

[0033] As Figures 1-9 shown, a zero-backlash harmonic reducer includes a rigid gear 1, a flexspline 2 installed inside the rigid gear 1, and a double semi-circular wave generator assembly 3 arranged inside the flexspline 2; the left end of the flexspline 2 has outer teeth 21; the rigid gear 1 has inner teeth 11 that cooperate with the outer teeth 21; the cross-section of the outer teeth 21 is semi-circular arc-shaped; the radius of the outer teeth 21 gradually decreases from left to right, forming conical outer teeth 21, and the radius of the circle of the leftmost outer teeth 21 is R 42 , and the radius of the circle of the rightmost outer teeth 21 is R 41 ; the double semi-circular wave generator assembly 3 includes a double semi-circular cam 31 and a flexible bearing 32 installed between the double semi-circular cam 31 and the flexspline 2; in this design, by setting the outer teeth 21 of the flexspline 2 as conical teeth and the cross-section as a semi-circular structure, the inner teeth 11 of the rigid gear 1 also cooperate with the outer teeth 21 of the flexspline 2 and are also conical structures. During the deformation process of the flexspline 2 under the action of the wave generator assembly, the left end of the flexspline 2 swings around the right end position. The left end of the flexspline 2 has a larger deformation. Therefore, the radius of the left end of the outer teeth 21 is set as the large end, and the right end is set as the small end. At the long axis position, this setting can improve the meshing degree with the rigid gear 1. At the short axis and the positions around the short axis, it can also make the outer teeth 21 completely disengage from the inner teeth 11. In addition, the setting of the cross-section as a semi-circular structure can also improve the smoothness of the relative movement between the outer teeth 21 and the inner teeth 11, and there will be no tooth jamming phenomenon. Therefore, the transmission accuracy of this solution is higher than that of the previous harmonic reducers and is applicable to mechanical engineering with high requirements for transmission accuracy.

[0034] The right ends of the flexspline 2 and the rigid gear 1 are connected by a crossed roller bearing 4; the crossed roller bearing 4 includes a roller bearing inner ring 41, a roller bearing outer ring 42, and rollers 43; the roller bearing inner ring 41 is fixed to the left end of the flexspline 2; the roller bearing outer ring 42 is fixed to the left end of the rigid gear 1; the rollers 43 are cross-arranged and installed between the roller bearing inner ring 41 and the roller bearing outer ring 42; a gasket 5 is also provided between the roller bearing inner ring 41 and the flexspline 2. In this design, the left-right position of the flexspline 2 relative to the rigid gear 1 is adjusted through the gasket 5, so as to improve the matching degree between the flexspline 2 and the rigid gear 1, making the processing accuracy requirements for the flexspline 2 and the rigid gear 1 not too high, and also achieving the effect of high-precision meshing.

[0035] The number of internal teeth 11 of the rigid gear 1 is two more than the number of external teeth 21 of the flexible gear 2, maximizing the transmission ratio.

[0036] The cone angle A of the external teeth 21 is 1° - 3°. According to multiple tests, setting it to 2° is more optimal.

[0037] The length of the external teeth 21 of the flexible gear 2 is 1 - 1.5 times the width of the flexible bearing 32.

[0038] A method for calculating the size and tooth profile of a bevel gear harmonic reducer includes the following steps:

[0039] 1) First, determine the semi-major axis length R7 after the deformation of the flexible gear 2; the wall thickness h1 of the flexible gear 2; the inner and outer radius difference h2 of the flexible bearing 32; the width W1 of the flexible bearing 32; the number of teeth Z2 = n of the flexible gear 2; the modulus m at the distribution circle of the external teeth 21 of the flexible gear 2; the external tooth circle radius R of the leftmost external tooth 21 of the flexible gear 2 42 and the external tooth circle radius R of the rightmost external tooth 21 of the flexible gear 2 41 ;

[0040] 2) According to the formula, calculate the external tooth distribution circle radius R6 = Z2 * m / 2 of the flexible gear 2 in the original state, the tooth pitch P = mπ at the distribution circle of the external teeth 21 of the flexible gear 2, and the length L1 = 1.2W1 of the external teeth 21 of the flexible gear 2, then the specification size of the flexible gear 2 can be obtained; where the cone angle A of the external teeth 21 of the flexible gear 2 = arctan((R 41 -R 42 ) / L1), and it is more preferable to set the cone angle A to 2°. Therefore, when determining the external tooth circle radius R of the leftmost external tooth 21 of the flexible gear 2 42 and the external tooth circle radius R of the leftmost external tooth 21 of the flexible gear 2 41 in step (1), try to adjust the taper to be close to 2° to achieve the optimal solution.

[0041] 3) Calculate using the formulas 2πR5 + 4R1 = 2πR6 and R1 + R5 = R7, and the distribution circle radius R5 = (πR6 - 2R7) / (π - 2) of the external teeth 21 of the flexible gear 2 after deformation on the double semi-circle can be obtained, and the eccentricity R1 of the double semi-circle after the deformation of the flexible gear 2 = π(R7 - R6) / (π - 2);

[0042] 4) Calculate the double semi-circle radius R8 of the double semi-circle wave generator assembly 3 = R5 - h1; the double semi-circle eccentricity R2 of the double semi-circle wave generator assembly 3 = R1;

[0043] 5) Calculate the double semi-circle radius R9 of the double semi-circle cam 31 = R8 - h2; the double semi-circle eccentricity R3 of the double semi-circle cam 31 = R2; then the specification size of the double semi-circle generator assembly can be obtained;

[0044] 6) Determine the number of internal teeth 11 of the rigid gear 1, Z1 = Z2 + 2;

[0045] 7) Calculate the motion law of the flexible gear 2. When the wave generator rotates clockwise by an angle ω, the flexible gear 2 rotates counterclockwise by an angle ω1 = ω(Z1 - Z2) / Z2 = 2ω / Z2;

[0046] 8) Taking the arc of the tooth tip circle of the rigid gear 1 as the reference, design the tooth profile of the envelope of the rigid gear 1 according to the motion law of the flexible gear 2 and the tooth profile of the external teeth 21 of the flexible gear 2. Calculate the primary envelope trajectory of the tooth profile in the tooth tip area of the flexible gear 2 in the tooth root area of the rigid gear 1, and calculate the secondary envelope trajectory of the tooth profile in the tooth root area of the flexible gear 2 in the tooth tip area of the rigid gear 1, which together form the complete tooth profile of the rigid gear 1, and form the tapered internal teeth 11 that match the tapered external teeth 21 of the flexible gear 2.

[0047] The above does not impose any limitation on the technical scope of the present novelty. Any modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present novelty.

Claims

1. A zero-backlash harmonic reducer, comprising a rigid gear, a flexible gear installed inside the rigid gear, and a double semi-circular wave generator assembly disposed inside the flexible gear; the left end of the flexible gear has external teeth; the rigid gear has internal teeth that cooperate with the external teeth; characterized in that: The cross-section of the external teeth is semi-circular arc-shaped; the radius of the external teeth gradually decreases from left to right, forming conical external teeth, and the radius of the leftmost external tooth circle is R 42 , and the radius of the rightmost external tooth circle is R 41 ; the double semi-circular wave generator assembly includes a double semi-circular cam and a flexible bearing installed between the double semi-circular cam and the flexspline; the right ends of the flexspline and the rigid ring are connected by a crossed roller bearing; the crossed roller bearing includes an inner ring of the roller bearing, an outer ring of the roller bearing and rollers; the inner ring of the roller bearing is fixed to the left end of the flexspline; the outer ring of the roller bearing is fixed to the left end of the rigid ring; the rollers are arranged crosswise between the inner ring of the roller bearing and the outer ring of the roller bearing; a gasket is further provided between the inner ring of the roller bearing and the flexspline; the number of internal teeth of the rigid ring is two more than the number of external teeth of the flexspline; the cone angle A of the external teeth is greater than 0° and less than 3°; the length of the external teeth of the flexspline is 1 to 1.5 times the width of the flexible bearing.

2. A method for calculating the size and tooth profile of a zero-backlash harmonic reducer, which is used to calculate the zero-backlash harmonic reducer as described in claim 1, and is characterized in that: 1) First, determine the length of the semi-major axis R7 after the flexspline is deformed; the wall thickness h1 of the flexspline; the difference in the inner and outer radii h2 of the flexure bearing; the width W1 of the flexure bearing; the number of teeth of the flexspline Z2 = n; the module at the pitch circle of the external teeth of the flexspline is m; the external tooth circle radius R of the leftmost external tooth of the flexspline 42 , the external tooth circle radius R of the rightmost external tooth of the flexspline 41 ; 2) Calculate the outer tooth distribution circle radius R6 = Z2*m / 2 of the flexspline in its original state according to the formula, the tooth pitch P = mπ at the outer tooth distribution circle of the flexspline, and the length L1 of the outer teeth of the flexspline = 1 to 1.5 times W1, then the specification size of the flexspline can be obtained; 3) Calculate the outer tooth distribution circle radius R5 = (πR6 - 2R7) / (π - 2) of the outer teeth of the flexspline on the double semi-circles after deformation through the formula, and the eccentricity R1 of the double semi-circles after deformation of the flexspline = π(R7 - R6) / (π - 2); 4) Calculate the double semi-circle radius R8 = R5 - h1 of the double semi-circle wave generator assembly; the double semi-circle eccentricity R2 of the double semi-circle wave generator assembly = R1; 5) Calculate the double semi-circle radius R9 = R8 - h2 of the double semi-circle cam; the double semi-circle eccentricity R3 of the double semi-circle cam = R2; then the specification size of the double semi-circle generator assembly can be obtained; 6) Determine the number of internal teeth Z1 of the rigid ring = Z2 + 2; 7) Calculate the motion law of the flexspline. When the wave generator rotates clockwise by an angle ω, the flexspline rotates counterclockwise by an angle ω1 = ω(Z1 - Z2) / Z2 = 2ω / Z2; 8) Based on the circular arc at the top of the teeth of the rigid ring, design the envelope tooth profile of the rigid ring according to the motion law of the flexspline and the tooth profile of the outer teeth of the flexspline, calculate the primary envelope trajectory of the tooth profile in the tooth top area of the flexspline in the tooth root area of the rigid ring, and calculate the secondary envelope trajectory of the tooth profile in the tooth root area of the flexspline in the tooth top area of the rigid ring, which together form the complete tooth profile of the rigid ring and form a conical internal tooth that matches the conical outer teeth of the flexspline.

3. The method for calculating the size and tooth profile of a zero-backlash harmonic reducer according to claim 2, wherein: In step (3), the length L1 of the outer teeth of the flexspline = 1.2W1.

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