Eccentric gear unit with rotationally symmetrical transmission elements

Abstract

Eccentric gear unit comprising a shaft (3) rotatable about an axis of rotation (2), which has at least one eccentric section (4) with a central eccentric axis (5) arranged at an acute angle (6) to the axis of rotation (2) and intersecting the axis of rotation (2) at a point “O1” (12), a planet (7) rotatably mounted on the eccentric section (4) about the eccentric axis (5), the planet (7) having planetary gear teeth (8), a first gear unit (13) with a first gear tooth which is in meshing contact with the planetary gear tooth (8) at a first point of engagement via rotationally symmetrical transmission elements (19), and a second gear unit (15) with a second gear tooth which is in meshing contact with the planetary gear tooth (8) at a second point of engagement via rotationally symmetrical transmission elements (19), wherein the transmission surfaces of the gear teeth in the first and second gear units (13; 15) are produced in this way,by traversing the trochoid, which is formed when the pitch circle of the planet (7) rolls over the pitch circle of the gear part (13; 15) according to a constant transmission ratio, with a profile identical or similar to that of the transmission element, thereby removing material from the gear part (13; 15), so that the transmission elements between the planet (7) and the gear parts (13; 15) perform a rolling motion, wherein the transmission surfaces created by the trochoids are only partially retained in the material of the gear parts (13; 15), whereas the transmission surfaces created by the planet trochoids in the planet (7) are completely incorporated into the material of the planet (7), characterized in that the rotatable shaft (3) has an additional second eccentric section (9) with a central second eccentric axis (10) which has an angle (11) to the axis of rotation (2),which is half as large and has the same sign as the angle (6) of the first eccentric axis (5), such that the 3 axes (2), (5) and (10) intersect at exactly one point “O1” (12), the center of rotation, and a two-part cage is mounted on this second eccentric section (9), which has a first cage part (17) and a second cage part (18), so that the transmission elements are received between the two cage parts with minimal to no play, which run in equal numbers with the trochoidal rolling channels (24) provided in the planet (7) and simultaneously perform a pure rolling motion in the trochoidal rolling channels (14) of the first gear part (13) and in the trochoidal rolling channels (16) of the second gear part (15) diametrically opposite to point “O1” (12).

Description

[0001] The present invention relates to an eccentric gear. State of the art

[0002] Key objectives in gearbox development include reducing manufacturing costs and increasing efficiency and power density. For example, in planetary gearboxes, different types of planets are investigated, and various rotationally symmetrical transmission elements are used instead of teeth.

[0003] Patent DE 199 07 912 A1 discloses an eccentric gear unit which has an eccentric arranged at an angle around the axis of rotation and rotatably mounts a planet gear. The planet gear meshes with both the stationary part of the gear unit and simultaneously with the output gear. This design thus consists of a fixed gear, a planet gear, and a rotatable output gear – a three-gear transmission. The disadvantage of this solution is that the type of gearing, whether involute, cycloidal, circular arc, or other similar, requires a three-dimensional form, which leads to high manufacturing costs and relatively low efficiency.

[0004] Another embodiment of a three-wheel transmission is known from DE 11 2016 002 380 T5. Here, the problem of planetary gearing was circumvented by using two independent gear sets, one meshing with the fixed gear and the other with the driven gear.

[0005] Early on, a proposal was described in US 1 748 907 A in which the planet meshes with the stationary gear but then transmits the power to the output via a wave-shaped groove using balls as transmission elements.

[0006] In the publications WO 2007 / 094 693 A1, AT 508 205 B1, DE 10 2014 001 263 A1 and US 9 863 480 B2, a planet running on an angular eccentric with two independent rows of magnets arranged on one or both sides as transmission elements is also used.

[0007] Early attempts were also made to replace involute gearing, which relies heavily on sliding friction, with a geometry of the transmission elements based on rolling friction. This is described in US 594,110 A for parallel and non-parallel axes. A similar solution is described in DE 10 2012 220 260 A1. In the first case, this results in sliding friction in the axes of the rollers, while in the second case, sliding friction arises at least on one gear due to forced guidance.

[0008] DE 10 2014 208 418 A1 describes a solution in which rollers are also used as transmission elements that move more or less in a controlled manner along tooth flanks.

[0009] US Patent 1,867,492 A describes the solution of the cycloidal gear in which rollers are used as transmission elements to mechanically convert torque and speed. This solution has proven effective, but only above a certain minimum gear ratio, and it requires some form of mass balancing.

[0010] German patent application DE 11 2017 001 685 T5 describes a solution in which balls are guided as transmission elements in corrugated transmission grooves in an eccentric drive element and then convert the mechanical quantities via corrugated transmission grooves in a centric output element. However, the solution shown here involves a large degree of relative motion between the transmission elements and the transmission grooves, resulting in low efficiency.

[0011] The publication EP 1 757 841 B1 describes a type of transmission in which the transmission elements are spheres that independently perform a spatial, oscillating motion. Their shape is determined by the shapes of the guide curves used, with the spherical transmission elements always located where the curve of the input element intersects the curve of the output element. This results in transmission elements, similar to a cycloidal gear, that are clamped between two flanks and cause a relative movement of the output with respect to the input. A disadvantage of this solution is the occurrence of alternating contact and clearance conditions of the transmission elements due to the absence of a ball cage.

[0012] In publications US 1 277 193 A, US 3 590 659 A, US 4 620 456 A and US 4 620 457 A, up to publications GB 2 085 994 A, US 4 960 003, US 4 829 851 A, US 4 643 047 A, US 5 312 306 A, US 5 443 428 A, RU 2 272 196 C2, EP 1 462 677 A1 and others, roller gears or ball gears, i.e. gears in which the transmission elements are balls or rollers, are described. All of these drives have in common that they provide cylindrical or spherical grooves in the form of trochoids with the same or similar pitch circle radius in a fixed, a driving, and a driven gear section, in which the transmission elements run and are located at the intersections of the curves. This forces constrained positions between the three gear sections, which, with a continuous input rotary motion, result in a non-continuous rotary motion at the output [Xu, Lizhong; SONG, Wentao; LI, Ran: Two-step sine movable tooth drive.In: Advances in Mechanical Engineering, Bd. 9, 2017, H. 6, S. 1-9. - ISSN 1687-8140 (E); 1687-8132 (P); DOI: 10.1177 / 1687814017712414. URL:. https: / / journals.sagepub.com / doi / pdf / 10.1177 / 1687814017712414?download=true [accessed 2024-03-11]. This type of gearbox has gained increased attention due to the development of modern manufacturing machines, as these gearboxes allow the sliding friction of classic gear drives to be largely replaced by rolling friction of the transmission elements. It should be noted that with a single planetary gear drive (a single ring of rotating elements) and a double planetary gear drive (two rings of rotating elements), the reduction ratio can be adjusted as needed. Some of the proposed solutions do not use cages, while others use cages for partial guidance of the rotating elements, which negatively affects the stability of the output speed, vibration behavior, and the wear of the transmission elements and their orbits.

[0013] Further designs are known from DE 10 2008 001 490 A1, from US 3 385 135 A and from DE 197 14 528 A1. Object of the invention

[0014] To improve the consistency of the output speed, the smooth running and the wear of gearboxes with rolling transmission elements, according to the preamble of claim 1, it is proposed to use a multi-part cage for the transmission elements, which, according to the invention, is controlled similarly to the planetary gear system, so that it keeps the transmission elements in the optimal paths calculated in theory, regardless of the pressure conditions prevailing between the transmission elements and their raceways and the speed at which the gearbox is operated. Description of the attached drawings: - Fig. Figure 1 shows the transmission according to claim 1 in longitudinal section; - Fig. 2 shows the one in Fig. 1 marked section AA through the transmission elements of the transmission according to the invention - Fig. 3 shows the one in Fig. 2 marked section BB in the direction of the rotation axis of a transmission element - Fig. 4 shows the one in Fig. 3 marked section CC, through the axis of rotation of a transmission element - Fig. Figure 5 shows an exploded view of the transmission according to the invention. Fig. 1 - Fig. Figure 6 shows the kinematic model of a prior art gearbox. - Fig. Figure 7 shows the kinematic model of the transmission according to the invention. - Fig. Figure 8 shows the arrangement of the trochoids of the first gear part, the planetary gear and the second gear part at a specific point in time - the transmission elements are shown reduced in size here. - Fig. Figure 9 shows a longitudinal section through the inventive gearbox with double planet and one output. - Fig. Figure 10 shows a longitudinal section through the transmission according to the invention with double planet and two outputs - Fig. Figure 11 shows a half-section of a bevel gear drive for deriving a trochoid. - Fig. Figure 12 shows the transmission according to the invention as a variant with a radial drive. Description

[0015] An advantageous configuration of the transmission 1 according to the invention consists of a rotary axis 2 along which the rotatable shaft 3 extends, which is rotatably mounted via bearing 1 31 in the transmission part 1 13 and via bearing 3 33 to the transmission part 2 15. The transmission part 2 15 is mounted via bearing 2 32 in the transmission part 1 13. A first eccentric section 4 is mounted on the shaft 3 at an angle θ 6 with its axis 5, and a second eccentric section 9 is mounted at an angle τ 11 with its axis 10. The axes 2, 5, and 10 intersect at the kinematic center “O1” 12 of the transmission. The planet 7 is mounted radially on the first eccentric section 4 via bearing 20 and axially via bearing 21. The cage parts 17 and 18 are mounted radially and axially on the second eccentric section 9 via bearing 22.The coordinate system in which the guide curves 34, 35 and 36 are defined lies in the kinematic center “O1” 12, according to which the rolling channels 14 in the first gear part, 16 in the second gear part and 24 in the planet 7 are placed and on which guide curves 34, 35 and 36 the transmission elements 19 move.The cage parts 17 and 18 are designed to accommodate the transmission elements 19 freely rotatable and with minimal play between them along the equator, such that the rotational movement imposed on the cage parts 17 and 18 by the shaft 3 and the free rotational movement of the cage parts 17 and 18 about the axis 10 of the second eccentric section 9 cause the transmission elements 19 to be supported in the rolling channels 14, on the transmission surfaces 27 or 28 - depending on the direction of rotation of the shaft 3 - of the first gear part 13 and in the rolling channels 24, on the transmission surfaces 25 or 26 - depending on the direction of rotation of the shaft 3 - of the planet 7, and to move rolling precisely along the guide cam 34 in the first gear part 13 and along the guide cams 36 for the rolling channels 24 in the planet 7. The forces arising from the dimensionally prestressed transmission elements 19 and the forces arising from the output torque, F. NThe reaction torque from planet 7 is introduced into the first gear part 13. Accordingly, the rotary motion is transmitted by the transmission elements 19 in the rolling channels 16, on the transmission surfaces 29 or 30 – depending on the direction of rotation of the shaft 3 – of the second gear part 15.

[0016] Another advantageous arrangement of the transmission according to the invention is used to achieve a higher reduction ratio. The transmission 37 thus constructed consists of a pivot axis 38 along which the rotatable shaft 39 extends, which is rotatably mounted via bearing 166 in the transmission part 150 and via bearing 368 with the transmission part 252. The transmission part 252 is mounted in the transmission part 150 via bearing 267. A first eccentric section 40 is mounted on the shaft 39 at an angle θ42 with its axis 41, and a second eccentric section 46 is mounted at an angle τ48 with its axis 47. The axes 38, 41, and 47 intersect at the kinematic center "O2" 49 of the gear unit 37. The double planetary gear 43 is radially supported at the first eccentric section 40 via the bearing 59 and axially supported via the bearings 60. The planetary gear 43 has two sets of roller channels with transmission surfaces 64 and 65 on either side of its equator.The three-part cage (see 17, 18, and 54) is radially and axially supported on the second eccentric section 46 via bearings 61. The transmission elements 58 are arranged in two sets, spaced apart from and at the equator of the three-part cage (see 17, 18, and 54), and are freely rotatable between cage parts 17 and 54 and 18 and 54, with minimal to no play. Their number and distance from the equator correspond to the rolling channels provided in the planetary gear 43. The kinematic center "O2" 49 contains the coordinate system in which the guide curves are defined in the first gear part 50, the second gear part 52, and the planetary gear 43. These guide curves determine the placement of the rolling channels in the first gear part 50, the second gear part 52, and the planetary gear 43, and the transmission elements 58 move along these guide curves. Reference symbol list 1. Gearbox according to the invention 2. Axis of rotation 3 Rotating shaft 4 First eccentric section 5 First eccentric axis 6 Angles of the first eccentric section 7 Planet 8 planetary gearing 9 Second eccentric section 10 Second eccentric axis 11 Angles of the second eccentric section 12 Intersection of the two eccentric axes: “O1” 13 First gearbox part 14 rolling channels for the transmission elements in the first gear section 15 Second gearbox part 16 rolling channels for the transmission elements in the second gearbox part 17 First cage part, guided according to the invention 18 Second cage part, guided according to the invention 19 Transmission element 20 Radial bearing of the planet 21 Axial bearing of the planet 22 Radial-Axial Mounting of the Cage Parts 23 contact surfaces on the cage parts for the transmission elements 24 rolling channels in the planet 25 First transmission surfaces in the planet 26 Second transmission surfaces in the planet 27 First transmission surfaces in the first gear section 28 Second transmission surfaces in the first gear section 29 First transmission surfaces in the second gear section 30 Second transmission surface in the second gear part 31 Warehouse 1 32 storage units 2 33 warehouses 3 34 Guide curve in the first gearbox part 35 Guide curve in the second gearbox part 36 guiding curves in the planet 37 Inventive gearbox with double planet 38 Rotary axis 39 Rotating shaft 40 First eccentric section 41 First eccentric axis 42 Angles of the first eccentric section 43 Double Planet 44 First planetary gearing 45 Second planetary gearing 46 Second eccentric section 47 Second eccentric axis 48 Angles of the second eccentric section 49 Intersection of the two eccentric axes: “O2” 50 First gearbox part 51 Running surfaces of the transmission elements in the first gearbox part 52 Second gearbox part 53 Running surfaces of the transmission elements in the second gearbox part 54 Middle cage part, guided according to the invention over the transmission elements 55 Lead-in surface of the first set of transmission elements on the first cage part 56 Lead-in surface of the first set of transmission elements on the middle cage part 57 First set of transmission elements 58 Second set of transmission elements 59 Radial bearing of the planet 60 Axial bearing of the planet 61 Radial-Axial Mounting of the Double Cage 62 contact surfaces of the transmission elements of the first set in the cage 63 Starting surface of the first set of transmission elements on the second cage part 64 transmission surfaces of the first set of transmission elements in the planet 65 transmission surfaces of the second set of transmission elements in the planet 66 Warehouse 1 67 Warehouse 2 68 storage 3 69 Inventive gearbox with double planet and two output parts 70 Third gearbox part 71 Transmission surfaces of the first set of transmission elements in the third gear section 72 storage units 4 73 Cage in standard design and function according to the state of the art 74 Track line, or guide curve of the transmission elements in the first gearbox part 75 Track line, or guide curve of the transmission elements in the second gearbox part 76 A selected point on the selected tooth of gear 1 77 The tooth flank of the selected tooth 78 A selected tooth of gear 1 79 Bevel gear 1 80 Bevel gear 2 81 bevel gear 82 Separation plane between gearbox part 1 and gearbox part 2 83 Subcircle of the transmission elements 84 Gearbox according to the invention with radial drive 85 Drive direction 86 Housing, first gearbox part 87 Output, second gearbox part 88 Drive with Planet 89 Drive element, here gearing 90 Drive shaft bearing 91 Output shaft bearing 92 Planet, outer 93 Radial bearing of the planet 94 Axial bearing of the planet 95 Transmission element 96 Two-part cage, guided according to the invention 97 Axial-radial bearing of the cage parts 98 rolling channels in the first gearbox section 99 rolling channels in the second gearbox part 100 Abwälzkanäle im Planeten Angeführte Druckschriften 1. DE 19 907 912 A1 2. DE 11 2016 002 380 T5 3. US 1 748 907 A 4. WO 2007 / 094 693 A1 5. AT 508 205 B1 6. DE 10 2014 001 263 A1 7. US 9 863 480 B2 8. US 594 110 A 9. DE 10 2012 220 260 A1 10. DE 10 2014 208 418 A1 11. US 1 867 492 A 12. DE 11 2017 001 685 T5 13. EP 1 757 841 B1 14. US 1 277 193 A 15. US 3 590 659 A 16. US 4 620 456 A 17. US 4 620 457 A 18. GB 2 085 994 A 19. US 4 960 003 A 20. US 4 829 851 A 21. US 4 643 047 A 22. US 5 312 306 A 23. US 5 443 428 A 24. RU 2 272 196 C2 25. EP 1 462 677 A1 26. XU, Lizhong; SONG, Wentao; Li, Ran :Two-step sine movable tooth drive. In: Advances in Mechanical Engineering, Bd. 9, 2017, H. 6, S. 1-9. - ISSN 1687-8140 (E); 1687-8132 (P); DOI: 10.1177 / 1687814017712414. URL: https: / / journals.sagepub.com / doi / pdf / 10.1177 / 16878140177124147? download=true [abgerufen am 2024-03-11] 27. DE 10 2008 001 490 A1 28. US 3 385 135 A 29. DE 197 14 528 A1

Claims

[1] Eccentric gear unit comprising a shaft (3) rotatable about an axis of rotation (2), which has at least one eccentric section (4) with a central eccentric axis (5) arranged at an acute angle (6) to the axis of rotation (2) and intersecting the axis of rotation (2) at a point “O1” (12), a planet (7) rotatably mounted on the eccentric section (4) about the eccentric axis (5), the planet (7) having planetary gearing (8), a first gear unit (13) with a first gear which is in meshing contact with the planetary gearing (8) at a first point of engagement via rotationally symmetric transmission elements (19), and a second gear unit (15) with a second gear which is in meshing contact with the planetary gearing (8) at a second point of engagement via rotationally symmetric transmission elements (19), wherein the transmission surfaces of the gears in the first and in the second gearbox part (13;15) are produced by traversing the trochoid that is formed when the pitch circle of the planet (7) rolls over the pitch circle of the gear part (13; 15) according to a constant transmission ratio, with a profile identical or similar to that of the transmission element, thereby removing material from the gear part (13; 15), so that the transmission elements between the planet (7) and the gear parts (13; 15) perform a rolling motion, wherein the transmission surfaces created by the trochoids are only partially retained in the material of the gear parts (13; 15), whereas the transmission surfaces created by the planet trochoids in the planet (7) are completely incorporated into the material of the planet (7); characterized by, that the rotatable shaft (3) has an additional second eccentric section (9) with a central second eccentric axis (10) which has an angle (11) to the axis of rotation (2) that is half as large and has the same sign as the angle (6) of the first eccentric axis (5), such that the 3 axes (2), (5) and (10) intersect at exactly one point “O1” (12), the center of rotation, and a two-part cage is mounted on this second eccentric section (9), which has a first cage part (17) and a second cage part (18), such that the transmission elements are received between the two cage parts with minimal to no play,which run in the same number with the trochoidal rolling channels (24) introduced in the planet (7) and simultaneously perform a pure rolling motion in the trochoidal rolling channels (14) of the first gear part (13) and in the trochoidal rolling channels (16) of the second gear part (15) diametrically opposite point “O1” (12). [2] Eccentric gear unit according to claim 1, characterized by , that a two-part cage is provided, which is mounted on the drive shaft over its own eccentric section, which receives the transmission elements (19) in a ring shape along its equator. [3] Eccentric gear unit according to claim 1, characterized by , that the transmission elements (19) are arranged in a three-part cage in two planes parallel to the equatorial plane of the cage and spaced apart from the equatorial plane. [4] Eccentric gear unit according to any one of claims 1 to 3, characterized by, that the transmission elements (19) are designed as spheres and the profiles of the rolling channels (14; 16; 24) are shaped with a corresponding conformity to the spheres. [5] Eccentric gear unit according to any one of claims 1 to 3, characterized by , that the transmission elements (19) are designed in a torus shape. [6] Eccentric gear unit according to any one of claims 1 to 5, characterized by , that the rolling channels (24; 16, 24) in the area of ​​the reversal points in the extreme angular positions of the planet (7) are cleared so that no radial and axial constraints arise. [7] Eccentric gear unit according to any one of claims 1 to 6, characterized by, that the trochoids used to manufacture the rolling channels (14; 16; 24) in the gear parts (13; 15) and the planet (7) as well as the path of the transmission elements (19) correspond exactly to that path of a selected point on the tooth flank (77) of one tooth of one gear opposite the other in an equivalent bevel gear (81) with involute or similar gearing. [8] Eccentric gear unit according to any one of claims 1 to 6, characterized by , that the trochoids used to manufacture the rolling channels (14; 16; 24) in the gear parts (13; 15) and the planet (7) as well as the path of the transmission elements (19) correspond exactly to that path of a point in the middle of the tooth width of a tooth, on the pitch circle of one gear opposite the other in an equivalent bevel gear (81) with involute or similar gearing. [9] Eccentric gear unit according to any one of claims 1 to 6, characterized by, that the trochoids used to manufacture the rolling channels (14; 16; 24) in the gear parts (13; 15) and the planet (7) as well as the path of the transmission elements (19) correspond exactly to that path of a selected point in the volume of one tooth of one gear opposite the other in an equivalent bevel gear (81) with involute or similar gearing. [10] Eccentric gear unit according to any one of claims 1 to 6, characterized by , that the trochoids used to manufacture the rolling channels (14; 16; 24) in the gear parts (13; 15) and the planet (7) as well as the path of the transmission elements (19) correspond exactly to that path of a selected point outside the volume of one tooth of one gear opposite the other in an equivalent bevel gear (81) with involute or similar gearing. [11] Eccentric gear unit according to any one of claims 1 to 10, characterized by, that a variant according to the invention (84) is designed such that the drive is provided from the radial direction (85), from the outside and thereby the two eccentric areas act outside the transmission elements (19), while maintaining the position of the eccentric axes.

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