Planar wave nutation transmission reducer and gear cutting method

Abstract

To provide a planar wave nutation transmission reducer in which the drawbacks have been overcome. [Solution] A plane wave low-tooth difference speed reducer in which the end face teeth nutate, employing a structure similar to a drum gear coupling, the fixed ring gear is a cylindrical straight-tooth internal gear, used in combination with a drum external gear of the same number of teeth, the tooth tips of the drum external gear are spherical and the center of the sphere is O, and as the crank of the input shaft rotates, the drum external gear achieves plane wave nutation around point O while limiting the rotation of the nutation gear.

Description

Technical Field

[0001] The present invention belongs to the design and processing technology of nutation transmission reducers, and more specifically relates to a planar wave differential reducer with end face teeth nutating.

Background Art

[0002] In recent years, due to many characteristics such as a simple and compact structure, a large reduction ratio, and rigid transmission, nutation transmission reducers have emerged as a new force in the field of wave differential reducers and are being actively developed. Compared with a cylindrical surface wave reducer composed of a rigid internal cylindrical gear and a flexible external cylindrical gear that are usually used in large quantities, it is inevitable that the material selection is strict and the manufacturing becomes difficult like that of a flexible external thin-walled cylindrical gear. At the same time, rigid transmission is realized, which is advantageous for improving transmission accuracy.

Summary of the Invention

Problems to be Solved by the Invention

[0003] However, in the current design of nutation transmission reducers, the nutation is realized by the internal bevel gear and the differential external bevel gear with a small number of teeth difference through conical surface wave (harmonic). However, the internal bevel gear is difficult to process with the current existing bevel gear hobbing machines, resulting in new manufacturing difficulties. Also, the mechanism for restricting the rotation of the nutation gear is often not ideal.

[0004] [[ID=二十六]]In view of the above, the planar wave differential reducer with end face teeth nutating according to the present invention adopts the following design and hobbing technical means in order to overcome these drawbacks. Its technical features are as follows.

Means for Solving the Problems

[0005] 1. Adopting a structure similar to a drum gear coupling, the fixed ring gear is a cylindrical straight-tooth internal gear, used in combination with a drum external gear of the same number of teeth, the tooth tips of the drum external gear are spherical, the center of the sphere is O, the drum external gear achieves planar wave nutation around point O, while restricting the rotation of the nutation gear, eliminating the need to separately arrange a mechanism to restrict the rotation of the nutation gear.

[0006] 2. The drum external gear of the drum gear coupling is manufactured by hobbing it according to the conjugate tooth surface principle provided by the Chinese invention patent "Hobbed Drum Gear Device" (Chinese invention patent registration number 87101897, inventor: Peng Fuhua), ensuring that all tooth surfaces of the inner and outer teeth of the drum gear coupling exhibit precise line contact, thereby maintaining a constant instantaneous transmission ratio and being advantageous for the operating life of the drum gear coupling.

[0007] 3. The nutation gear is a straight-toothed plane bevel gear with a plane pitch cone. The pitch cone plane overlaps with the centering end plane passing through point O of the drum gear of the drum gear coupling. The two are fixedly connected as a single unit, completing a plane wave nutation together and limiting the rotation of the nutation gear.

[0008] 4. Using a German bevel gear shaper, such as the RAPID 25KH, the cutting direction of the tool can be adjusted according to the tooth root angle required for the output bevel gear. Using the virtual plane bevel gear machining principle, the teeth of the output bevel gear (number of teeth Z2) are created and cut out, while the teeth of the drive gear are milled according to the plane bevel gear (number of teeth Z1) using a linear cutting milling cutter and indexing on a circular turntable. Both machining processes are straightforward.

[0009] 5. Using bevel gear shapers from the United States, China, etc., the cutting direction of the tool is perpendicular to the cradle axis and cannot be adjusted according to the tooth root angle required for the output bevel gear. It is only possible to create and cut the teeth of the output bevel gear (number of teeth Z2) by the virtual flat-top bevel gear (bevel gear with a face angle of 90 degrees) machining principle. The chute gear is formed by milling the teeth of a flat-top planar bevel gear (number of teeth Z1) using a linear cutting milling cutter and indexing on a circular turntable, and both machining processes are still simple.

[0010] The present invention will be described sequentially below with reference to the drawings. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a diagram illustrating the motion of hobbing the external gear of a drum using the conjugate tooth surface principle of the Chinese invention patent "Hob-cutting drum gear device" (registration number 87101897). [Figure 2] Figure 2 is a schematic cross-sectional view of the structure of a plane wave low-tooth difference speed reducer in which the end face teeth undergo nutation. [Figure 3] Figure 3 is a cross-sectional parameter diagram of a virtual plane bevel gear (number of teeth Z1), which is a driven gear. [Figure 4] Figure 4 is a cross-sectional parameter diagram of a conjugate drive gear, a virtual flat-top plane bevel gear (number of teeth Z1), and a conjugate output bevel gear (number of teeth Z2). [Figure 5] Figure 5 is a schematic cross-sectional view of the structure of a plane wave low-tooth difference speed reducer in which the end face teeth nutate, suitable for small-dimensional specifications. [Modes for carrying out the invention]

[0012] As shown in Figure 1, a hobbing drum gear device 2, according to a Chinese invention patent, is mounted on the slewing table 1 of the hobbing machine, and it is required that the slewing axes II of both devices overlap. The work axis II-II of device 2 (see the above patent document for detailed structure) intersects with the slewing axis II at point O, and the vertical position is adjusted so that point O is at the center of the spherical tooth tip of the spherical surface of the drum gear when the workpiece 3, i.e., the external gear drum, is mounted on the work axis II-II. The angle Σ between the two axes, the slewing axis II and the work axis II-II, is adjusted by an eccentricity mechanism within device 2, and device 2 also completes the process of eliminating the rotation of the work axis II-II itself when the work axis II-II rapidly rotates around the slewing axis II. In this way, wave nutation of the end plane passing through point O of the workpiece 3 is realized.

[0013] In the diagram, the hobbing machine's rotating table 1 rotates ω2 along with the device 2, and the hob 4 rotates ω1 and moves Vf in the direction of the II axis, thereby completing the hobbing of the drum external gear according to the conjugate tooth surface principle.

[0014] As shown in Figure 2, in the figure, 1 is the casing, and the nutation motion is completed by the relative motion between the cylindrical straight-toothed internal ring gear 2 fixed to the casing and the drum external gear 3. The shapes of members 2 and 3 are similar to those of a normal drum gear coupling, but member 3 is manufactured by hobbing the drum external gear according to the conjugate tooth surface principle described above. Member 4 is a nutation gear fixedly connected to member 3, and is itself a planar bevel gear with a number of teeth Z1. The apex O of the cone must coincide with the spherical center O of the tooth tip of member 3, and the reference cone surface of the planar bevel gear also overlaps with the centering end plane passing through point O of member 3.

[0015] Member 4 is attached to the crank portion of the input shaft of member 6 via member 5, which is a group of thrust bearings that receive radial and axial forces. The angle between the axis II-II of the crank and the pivot axis II of the input shaft is Σ, and the intersection of the two axes must also coincide with the apex O of the cone. Member 7 is an output bevel gear with Z2 teeth, which meshes with member 4, a nutation gear which is a plane bevel gear with Z1 teeth, and the apex of the cone is still O. Members 8 and 9 in the figure are both groups of thrust bearings that receive radial and axial forces.

[0016] If the rotational speed of the input shaft is n1 and the rotational speed of the output shaft is n2, then the reduction ratio i = n1 / n2 = -Z2 / (Z1-Z2), where n1 and n2 are in opposite directions.

[0017] As shown in Fig. 3, by using a German bevel gear shaper, such as RAPID 25KH, and performing tooth cutting according to the virtual bevel gear principle, the nutating gear is formed by tooth cutting in accordance with the virtual bevel gear (tooth number Z1) of the gear shaper. On an ordinary milling machine, teeth can be milled by using a straight-edge forming milling cutter and indexing a circular turntable. The output bevel gear (tooth number Z2) is generated and cut by using a gear shaper and has the structure shown in the structural schematic diagram of Fig. 2.

[0018] Fig. 3 shows the main parameters of the bevel gear (tooth number Z1) of the nutating gear. The tooth numbers of this bevel gear and the output bevel gear (tooth number Z2) are determined as follows.

[0019] 1) First, make the reduction ratio i = n1 / n2 = -Z2 / (Z1 - Z2). 2) Determine the tooth number difference ΔZ and Z1 and Z2, and set ΔZ = (Z1 - Z2) = 1 - 4, Z2 = iΔZ, Z1 = Z2 + ΔZ. 3) Determine the large end diameter D of the teeth of the output bevel gear according to the strength requirements. 4) The reference cone angle δ of the output bevel gear, Sinδ = Z2 / Z1 5) The length of the reference cone generatrix at the large end of the output bevel gear, Le = D / 2Sinδ 6) The diameter of the nutating gear, D0 = 2Le 7) The module at the large end of the teeth, m = D0 / Z1 8) The tooth tip angle γ, tanγ = (0.8 - 1)m / Le. Here, 0.8 is calculated for low teeth and can effectively avoid meshing interference. 9) The tooth width b of the output bevel gear = (1 / 3 - 1 / 4)Le 10) The shaft angle Σ, Σ = 90° - δ 11) The tooth profile angle α of the teeth, α = 20°, 225°. When the tooth profile angle is larger, interference is less likely to occur.

[0020] Figure 4 is a cross-sectional parameter diagram of the nutating gear, i.e., the virtual flat-top face bevel gear (tooth number Z1) and the conjugate output bevel gear (tooth number Z2) during gear shaping. The nutating gear shown is a flat-top face bevel gear, with its axis of rotation being II-II, pitch cone angle being 90°, and it is a face bevel gear. Since its tooth tip is parallel to the pitch plane and is a plane at a distance h1 from the pitch plane, it is called a flat-top face bevel gear, and h1 is for the tooth tip of the small end of the tooth. Obviously, compared with the standard Gleason bevel gear, the tooth tip part of the tooth of the flat-top face bevel gear is incomplete, and the tooth root part of the tooth of the conjugate output bevel gear is incomplete. However, during the nutation process, the tooth number difference ΔZ between the two is extremely small, and at the same time, the number of meshing teeth is large, so normal operation can still be maintained. V in the figure indicates the tooth cutting direction of the cutter when the virtual flat-top face bevel gear generates and cuts the teeth of the output bevel gear (tooth number Z2), and V⊥II-II, which meets the limitation that the cutter cutting direction of bevel gear shapers in the United States, China, etc. is perpendicular to the cradle axis. The top edge of the cutter cuts the bottom of the tooth groove of the output bevel gear (tooth number Z2), and the height of the top edge of the cutter needs to be adjusted until the distance from the pitch plane is h1 + c, where c is the tooth tip clearance.

[0021] The structure shown in Figure 2 above is suitable for a plane wave type planetary gear reducer with large dimensional specifications and nutating end teeth. When the dimensional specifications are small, in order to facilitate the arrangement of bearings, a structure as shown in Figure 5 can be adopted.

[0022] As shown in Figure 5, in the figure, 1 is the casing, and the nutation motion is completed by the relative motion between the cylindrical straight-toothed internal ring gear 2 fixed to the casing and the drum external gear 3. The shapes of members 2 and 3 are similar to those of a normal drum gear coupling, but member 3 is manufactured by hobbing the drum external gear according to the conjugate tooth surface principle described above. Member 4 is a nutation gear fixedly connected integrally with member 3, and is itself a planar bevel gear with the number of teeth Z1. The apex O of the cone must coincide with the spherical center O of the tooth tip of member 3, and the reference cone plane of the planar bevel gear also overlaps with the centering end plane that passes through point O of member 3. The difference from Figure 2 is that member 4 does not have a hole, but has a flat end boss B, and the plane B is the reference cone plane of the planar bevel gear that includes point O.

[0023] By being mounted on the inclined plane at the left end of the input shaft member 6, the angle between the axis II-II of member 5, i.e., the thrust ball bearing, member 4, which receives axial force, and the pivot axis II of the input shaft member 6 becomes Σ, and the intersection of the two axes coincides with the apex O of the cone. Member 7 is an output bevel gear with Z2 teeth, and meshes with the plane bevel gear i.e., the nutation gear of member 4 with Z1 teeth, and the apex of the cone is still O. The difference from Figure 2 is that the right end of member 7 is formed on the A cone surface, that is, it is manufactured so that the reference cone angle δ of the output bevel gear is Sinδ = Z2 / Z1, and during operation, the A cone surface of member 7 is in close contact with the B plane of member 4, thereby realizing nutation between plane B and cone surface A.

[0024] Members 8 and 9 in the diagram are all thrust bearing groups, which receive radial and axial forces. By adjusting the axial relative position of thrust bearing groups 8 and 9, the contact state between plane B and conical surface A can be adjusted.

[0025] The main features of this invention can be summarized as follows.

[0026] 1. The drum external gear achieves planar wave nutation using a drum gear coupling hobbed according to the conjugate tooth surface principle of the Chinese invention patent "Hobbed Drum Gear Device" (registration number 87101897). All tooth surfaces of the inner and outer teeth exhibit precise line contact, maintaining a constant instantaneous transmission ratio and benefiting the operating life of the drum gear coupling. Using this invention eliminates the need to separately arrange a mechanism to limit the rotation of the nutation gear.

[0027] Compared to Japanese-made gearboxes that achieve nutation using bevel gears, cylindrical gears are easier to machine and offer advantages in reducing manufacturing costs.

[0028] 2. Compared to cylindrical wave-driven speed reducers currently in widespread use, which consist of rigid internal cylindrical gears and flexible external cylindrical gears, this design avoids the strict material selection and manufacturing difficulties associated with flexible external thin-walled cylindrical gears, while simultaneously achieving rigid transmission and offering advantages in improving transmission accuracy.

[0029] 3. Compared to a conical wave gear reducer where nutation is driven by internal bevel gears and external bevel gears with small tooth difference, the manufacturing difficulty of internal bevel gears, which are difficult to machine with existing bevel gear cutting machines, is eliminated.

[0030] 4. The structure is simple and highly reliable, which is advantageous for reducing manufacturing costs. Furthermore, bearings can be arranged and selected according to different standard dimensions, meeting the needs of various industries.

[0031] The following technologies are disclosed based on the above description.

[0032] (Technology 1) A plane wave small tooth difference reduction gear in which end face teeth nutate, employing a structure similar to a drum gear coupling, the fixed ring gear is a cylindrical straight tooth internal gear, used in combination with a drum external gear of the same number of teeth, the tooth tips of the drum external gear are spherical and the center of the sphere is O, and as the crank of the input shaft rotates, the drum external gear achieves plane wave nutation around point O, while limiting the rotation of the nutation gear, a plane wave small tooth difference reduction gear.

[0033] (Technology 2) The external gear of the drum gear coupling has all of its internal and external tooth surfaces making precise line contact, maintaining a constant instantaneous transmission ratio, as described in Technology 1 for the planar wave small tooth difference reduction gear.

[0034] (Technology 3) The nutation gear is a straight-toothed plane bevel gear with a plane pitch cone, the pitch cone plane overlapping with the centering end plane passing through point O of the drum gear of the drum gear coupling, and the two are fixedly connected as a single unit, completing the plane wave nutation together while limiting the rotation of the nutation gear, as described in Technology 1.

[0035] (Technology 4) A gear cutting method in which a nutation drive gear is shaped and cut according to a virtual plane bevel gear (number of teeth Z1) by using a German bevel gear shaper, such as the RAPID 25KH, and the output bevel gear (number of teeth Z2) is created and cut using the gear shaper, based on the principle of virtual plane bevel gears.

[0036] (Technology 5) A gear cutting method in which a nutation drive gear is shaped and cut according to a virtual flat-topped bevel gear (number of teeth Z1) by using a bevel gear shaper from the United States, China, etc., and cutting the teeth according to the virtual flat-topped bevel gear principle, and an output bevel gear (number of teeth Z2) is created and cut using a gear shaper.

[0037] (Examples) The geometric elements of the output bevel gear and nutation gear of a plane wave low-tooth difference speed reducer with a reduction ratio of i=60 and a large end diameter D=100mm of end face teeth of the output bevel gear were designed and calculated, and the output bevel gear was cut using a German bevel gear gear shaper.

[0038] 1) Determine the tooth difference ΔZ = 1. 2) Calculate the number of teeth Z2 of the output bevel gear, and find that Z2 = iΔZ = 60. 3) Calculate the number of teeth Z1 of the drive gear, and you get Z1 = Z2 + ΔZ = 61. 4) The reference cone angle δ of the output bevel gear is given by Sinδ = Z² / Z¹, where δ = arcSin(60 / 61) = 79.609° 5) Generator length of the big end reference cone of the output bevel gear: Le = D / 2Sinδ = 50.8333 mm 6) Chapter: Diameter of the drive gear, D0 = 2Le = 101.6667 mm 7) Tooth big end module, m=D0 / Z1=1.6667mm 8) For the tooth terminal angle γ, tanγ = (0.8~1)m / Le. Calculating for a normal tooth with a tooth terminal height coefficient of 1, γ = arctan(1 × 1.6667) / 50.8333 = 1.8783°. 9) Tooth width of output bevel gear b = Le / 4 = 12.7 mm 10) Axis angle Σ, Σ=90°-δ=10.391° 11) Let α be the tooth profile angle, where α = 20°. 12) Σ(10.391°) > 2γ(3.7566°) is verified and passes.

Claims

1. A plane wave type small tooth difference reduction gear in which the end face teeth undergo nutation, It employs a structure similar to a drum gear coupling, with a fixed ring gear being a cylindrical straight-tooth internal gear, used in combination with a drum external gear of the same number of teeth. The tooth tips of the drum external gear are spherical, with a spherical center of O. As the input shaft crank rotates, the drum external gear achieves a planar wave nutation around point O, while limiting the rotation of the nutation gear. Planar wave small tooth difference speed reducer.

2. The drum gear coupling's external gears, both internal and external, exhibit precise line contact on all tooth surfaces, maintaining a constant instantaneous power transmission ratio. Planar wave small tooth difference reduction gear according to claim 1.

3. The nutation gear is a straight-toothed plane bevel gear with a plane pitch cone. The pitch cone plane overlaps with the centering end plane passing through point O of the drum gear of the drum gear coupling, and the two are fixedly connected as a single unit, completing a plane wave nutation together while restricting the rotation of the nutation gear. Planar wave small tooth difference reduction gear according to claim 1.

4. Using a German bevel gear shaper, such as the RAPID 25KH, the gear cutting is performed according to the virtual planar bevel gear principle, shaping and cutting the drive gear according to the virtual planar bevel gear (number of teeth Z1), and then creating and cutting the output bevel gear (number of teeth Z2) using the gear shaper. Tooth cutting method.

5. Using bevel gear shapers from the United States, China, etc., the gear cutting is performed according to the virtual flat-topped, planar bevel gear principle. The nutation drive gear is shaped and cut according to the virtual flat-topped, planar bevel gear (number of teeth Z1), and the output bevel gear (number of teeth Z2) is created and cut using the gear shaper. Tooth cutting method.

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