Mechanical deceleration assembly

Abstract

A mechanical deceleration assembly includes: a first sun gear; a first annular wheel concentrically arranged around the first sun wheel such that the first sun wheel and the first annular wheel share a first axis of symmetry; an at least hollow first planetary member comprising a first cylindrical section in frictional engagement with an outer surface of the first sun gear and an inner surface of the first annular gear, the first planetary member being arranged to rotate about a second axis, wherein the first planetary member comprises a circumferential first groove and a circumferential second groove, the circumferential first groove and the circumferential second groove being spaced apart from each other by a first cylindrical section; also included is at least a first alignment ring secured to the first sun gear or the first ring gear to prevent movement along the first axis of symmetry and protruding into the first groove or the second groove.

Description

Technical Field

[0001] The present invention relates to a mechanical speed reduction assembly including a plurality of rotationally symmetric members and to a method of assembling the mechanical speed reduction assembly. Depending on which member receives the input torque, the proposed mechanical speed reduction assembly is adapted to change the magnitude or direction of the output rotational speed relative to the input rotational speed.

[0002] WO 2018 / 178380 A1 discloses a compound planetary friction transmission including a first sun gear and planetary gears, wherein the first sun gear engages with the planetary gears, the planetary gears being arranged with two outer portions having a first radius and a central portion having a second radius, wherein the second radius is different from the first radius and a transition region is provided between the outer portion and the central portion, and wherein an outer annular toroidal surface and a central annular toroidal surface are provided which are drivingly engaged with the planetary gears, wherein the outer annular toroidal surface has two portions, the central annular toroidal surface being provided between the two portions along the length of the planetary gears, wherein the first sun gear is in frictional engagement with the outer portions of the planetary gears, the said outer portions of the planetary gears are in frictional engagement with portions of the outer annular toroidal surface and the central annular toroidal surface is in frictional engagement with the central portions of the planetary gears, wherein the planetary gears are both hollow and can be compressed continuously along their entire length spanning the outer portions, the transition region and the central portion. Background Art

[0003] Problems and Solutions

[0004] The problem to be solved is to provide an improved mechanical speed reduction assembly.

[0005] This problem is solved by the mechanical speed reduction assembly according to claim 1 and also by the preferred embodiments according to the dependent claims.

[0006] The mechanical speed reduction assembly (first aspect) according to the present invention includes a first sun gear and a first annular gear. The first annular gear is arranged concentrically around the first sun gear such that the first sun gear and the first annular gear share a first axis of symmetry. The assembly further includes at least one hollow first planetary member having a first cylindrical section which is in frictional engagement with the outer surface of the first sun gear and the inner surface of the first annular gear. The first cylindrical section serves as the running surface of the first planetary member. The first planetary member is arranged to rotate about a second axis and includes a circumferential first groove and a circumferential second groove which are spaced apart from each other by the first cylindrical section. The assembly further includes at least a first alignment ring which is fixed to the first sun gear or the first annular gear to prevent movement along the first axis of symmetry and which projects into the first groove or the second groove.

[0007] Since the alignment ring also protrudes into the first groove or the second groove, the alignment ring that is fixed to prevent movement along the first symmetry axis can prevent the undesired movement of the first planetary member along the first axis or the second axis. This can help reduce slippage and / or wear, particularly the slippage and / or wear caused by the relative rotation of the first planetary member during operation of the assembly.

[0008] In the prior art, planetary members are typically constrained by means of shafts and cam systems to achieve alignment of the planetary members with the sun gear and the ring gear. In the prior art, alignment features can be used to align the output member of the assembly with the axis of rotation of the planetary member.

[0009] The first planetary member of the present invention can move and rotate relative to more than one axis. The second axis of the planetary member is not fixed relative to the first symmetry axis. The output member of the assembly can be fixed by an external bearing. The alignment ring can urge the second axis to be more aligned with the first symmetry axis. The first alignment ring can provide a thrust bearing surface for applying a thrust on the first planetary member to urge the second axis to be more aligned with the first symmetry axis.

[0010] Furthermore, for any given amount of compressive force applied to the contact surface, a fixed amount of traction "thrust" can be obtained, as determined by the coefficient of friction. If any degree of skew occurs, the "angle" along which the traction thrust is vectorized will become non-parallel to the desired line of motion. Any component of the vector that is non-parallel to the allowed line of action will be lost. If the assembly is constrained against axial movement, these components must slide in the axial direction. The coefficient of friction during sliding is lower than the coefficient of friction during traction, resulting in additional losses. A skew angle may occur, which can cause the assembly to quickly lose traction. Changing the profile and position of the first alignment ring may affect this critical skew angle. By reducing the amount of thrust loss, the torque capacity and efficiency of the assembly are increased. By reducing the amount of slippage, abrasive wear of the components of the assembly can be reduced, and the service life of the assembly can be extended. Summary of the Invention

[0011] Unless otherwise stated, the preferred embodiments described below and explained by the dependent claims can be advantageously combined.

[0012] The assembly can be a single-stage planetary reduction assembly. At least one first planetary member can be supported by a planet carrier. The assembly can be part of a high-level multi-stage planetary reduction assembly.

[0013] The first alignment ring of an embodiment includes an alignment shoulder that is arranged to engage with the groove side surface of the first groove or the second groove, and the groove side surface is generally perpendicular to the second axis. The alignment shoulder is used to induce a stabilizing moment on the planetary member, and the direction and magnitude of the stabilizing moment urge the second axis to be more aligned with the first symmetry axis. The alignment shoulder can be a mechanical flange or a shoulder. The radial profile of the alignment shoulder is preferably straight, convex, concave, or of a complex geometry to meet the stability requirements implied by the shoulder position and the nominal dimensions of the component parts. The alignment shoulder can extend from the side surface of the first alignment ring that is perpendicular to the first axis or the second axis. Alignment shoulder

[0014] In one embodiment, the first groove and / or the second groove includes a mating shoulder that is arranged to engage with the alignment shoulder. The shape of the mating shoulder can be complementary to the alignment shoulder. A larger or smaller contact angle can be used to generate a larger or smaller stabilizing force. The profile of the mating shoulder can be identical to the profile of the alignment shoulder or can be deformed to allow for manufacturability. The radial profile of the mating shoulder is preferably straight, convex, concave, or of a complex geometry to meet the stability requirements implied by the shoulder position and the nominal dimensions of the component parts.

[0015] In another embodiment, the first annulus includes a first recess that extends circumferentially around the first symmetry axis and is arranged to partially receive the first alignment ring. Preferably, the first annulus includes a second recess that extends circumferentially around the first symmetry axis and is spaced from the first recess along the first symmetry axis, and the second recess is arranged to partially receive the first alignment ring. The first alignment ring can assist in being fixed in the recess to prevent rotation relative to the first annulus.

[0016] The first sun gear of another embodiment includes a first recess that extends circumferentially around the first symmetry axis and is arranged to partially receive the first alignment ring. Preferably, the first sun gear includes a second recess that extends circumferentially around the first symmetry axis and is spaced from the first recess along the first symmetry axis, and the second recess is arranged to partially receive the first alignment ring. The first alignment ring can assist in being fixed in the recess to prevent rotation relative to the first sun gear.

[0017] An embodiment includes a second alignment ring similar to the first alignment ring, and the second alignment ring will be partially arranged in the second recess. Preferably, the first alignment ring engages with the first groove and / or the second alignment ring engages with the second groove.

[0018] According to another embodiment, the first alignment ring, the first recess, and / or the second recess includes a curved crown. The curved crown may be bounded by a portion of a circle, preferably having a radius in the range of 0.025 mm to 25.4 mm, or a portion of an ellipse or a portion of a logarithmic curve. The curved crown of the first alignment ring may extend towards the circumferential surface of the first recess or the second recess or towards the groove side of the first groove or the second groove. Alternatively or additionally, the curved crown of the first groove or the second groove may project towards the circumferential surface of the first alignment ring or project from one of the groove sides to engage with the side surface of the first alignment ring. The curved crown may extend circumferentially around the first axis of symmetry or around the second axis. The curved crown may help protect the circumferential edges of the first alignment ring, the first recess, and / or the second recess from wear.

[0019] One embodiment includes at least a hollow second planetary member and a hollow third planetary member similar to the first planetary member. These planetary members are arranged around a first axis of symmetry, and each of these planetary members is in frictional engagement with the outer surface of the first sun gear and the inner surface of the first ring gear. In particular, a fourth planetary member similar to the first planetary member and the other planetary members may help reduce the torque to be transmitted by each of these planetary members. This embodiment can be used as a single-stage reduction assembly. Depending on which member of the assembly receives the input torque, the proposed mechanical reduction assembly is suitable for increasing the input rotational speed.

[0020] In a preferred embodiment, at least the first planetary member includes a second cylindrical section similar to the first cylindrical section, wherein the first groove or the second groove is arranged between the second cylindrical section and the first cylindrical section. At least the first planetary member may include a third cylindrical section similar to the first cylindrical section, wherein the first cylindrical section, the second cylindrical section, and the third cylindrical section are separated from each other by the first groove and the second groove. The first planetary member may be machined from a single blank. Alternatively, two of these cylindrical sections have been machined separately before being joined. One or more of the grooves may have been machined into the first planetary member by a turning operation.

[0021] Another embodiment further includes a second sun gear and a second ring gear, the second ring gear being arranged concentrically around the second sun gear, wherein the second sun gear and the second ring gear share the first axis of symmetry. The second cylindrical section is in frictional engagement with the outer surface of the second sun gear and the inner surface of the second ring gear. Depending on which member of the assembly receives the input torque, the proposed mechanical reduction assembly is suitable for increasing the input rotational speed. During the operation of this embodiment, one of the sun gears - preferably the second sun gear - may be rotationally fixed.

[0022] One embodiment further includes a bearing disposed about a first axis of symmetry, wherein the bearing engages the sun gear faces of the first sun gear and the second sun gear, these sun gear faces being perpendicular to the first axis of symmetry. The bearing can help reduce wear of the sun gears. During operation of the present embodiment, the bearing can help stabilize the first sun gear. The bearing can be a roller bearing or a needle bearing.

[0023] Another embodiment further includes a third annulus, wherein the first annulus is disposed between the second annulus and the third annulus, and at least the first planetary member - in particular the third cylindrical section - frictionally engages the inner surface of the third annulus. This embodiment can include a third sun gear, the outer surface of which frictionally engages at least the first planetary member - in particular its third cylindrical section - and wherein the first sun gear is disposed between the second sun gear and the third sun gear. There may be another bearing between the third sun gear and the first sun gear, allowing the first sun gear to rotate relative to the third sun gear. The planetary members of this embodiment can include a third cylindrical section, a second groove, a first cylindrical section, a first groove, and a second cylindrical section. One or more of the groove sides can include mating shoulders. This embodiment can be used as a two-stage planetary reduction assembly.

[0024] Preferably, the second annulus and the third annulus are rotationally coupled. The coupled annuli can be used as the torque output member of this embodiment.

[0025] A method of manufacturing a mechanical reduction assembly as described above (second aspect) preferably includes the following steps:

[0026] S1 Insert one of the alignment rings into one of the recesses of the first sun gear or the first annulus,

[0027] S2 Insert the alignment ring into the first groove or the second groove of at least the first planetary member,

[0028] S3 Dispose the first sun gear relative to the first annulus such that they are concentrically disposed and share a first axis of symmetry. Detailed Description

[0029] Further details and advantages of the present invention become apparent to those skilled in the art in accordance with the exemplary embodiments described below.

[0030] Figure 1A cross-section (left side) of an exemplary embodiment of a mechanical reduction assembly is shown. The assembly includes: a first sun gear 1; a first annulus gear 2, which is arranged concentrically around the first sun gear such that the first sun gear and the first annulus gear share a first axis of symmetry A; at least a hollow first planetary member 3, which includes a first cylindrical section 4 that is in frictional engagement with the outer surface of the first sun gear and the inner surface of the first annulus gear, and the first planetary member is arranged to rotate about a second axis B. The first planetary member includes a circumferential first groove 5 and a circumferential second groove 6, which are spaced apart from each other by the first cylindrical section. The assembly further includes at least a first alignment ring 7, which is fixed to the first annulus gear to prevent movement along the first axis of symmetry, and the at least first alignment ring projects into the first groove. Although only two planetary members 3, 9 are shown, the embodiment includes at least a third planetary member and a fourth planetary member (not shown) having a similar structure. In addition, the embodiment includes a second alignment ring 8, which is also fixed to the first annulus gear to prevent movement along the first axis of symmetry, and the second alignment ring projects into the second groove. Each of the alignment rings is partially held in a corresponding recess of the first annulus gear, and these recesses 10 are as Figure 1 shown on the right side.

[0031] Figure 2 A cross-section of another exemplary embodiment is shown. In addition to the Figure 1 members shown, the embodiment further includes a second sun gear 11 and a third sun gear 12, a second annulus gear 13 and a third annulus gear 14, at least a second planetary member 15 and a second alignment ring 16 similar to the first alignment ring. The first alignment ring 7 and the second alignment ring 8 are fixed to the first annulus gear to prevent movement along the first axis of symmetry and engage with the first groove and the second groove of the corresponding planetary members. Each of the alignment rings is partially held in a corresponding recess of the first annulus gear 2. Each planetary member includes a second cylindrical section 17 and a third cylindrical section 18. As shown, each of the first groove and the second groove is arranged between two of the cylindrical sections. Despite the grooves, each planetary member is a one-piece hollow structure.

[0032] The first cylindrical section 4 is in frictional engagement with the outer surface of the first sun gear 1 and the inner surface of the first annulus 2. The second cylindrical section 17 is in frictional engagement with the outer surface of the second sun gear 11 and the inner surface of the second annulus 13. The third cylindrical section 18 is in frictional engagement with the outer surface of the third sun gear 12 and the inner surface of the third annulus 14. Although only two planetary members are shown, the embodiment includes at least a third planetary member and a fourth planetary member. There is a first bearing 19 between the first sun gear and the second sun gear, and a second bearing 20 between the first sun gear and the third sun gear.

[0033] The embodiment is operable such that the first sun gear is driven. The first annulus is fixed against rotation. The second sun gear and the third sun gear are free to rotate. The second annulus and the third annulus are rotationally coupled and serve as a combined output member. The second and third cylindrical sections of the planetary members drive the second and third annuli to rotate about a first axis of symmetry while their first cylindrical sections roll along the inner surface of the first annulus. If operated in this manner, the assembly will serve as a two-stage reduction assembly.

[0034] Figure 3 A side view of an exemplary embodiment that is very similar to Figure 2 is shown. The embodiment includes ten hollow planetary members 3 arranged about a first axis of symmetry A. Each of these hollow planetary members transmits a portion of the total torque between each sun gear and the corresponding annulus.

[0035] Figure 4 A Figure 2 and Figure 3 cross-section of one of the planetary members 3 of the embodiment shown is presented. The planetary member includes (from left to right): a third cylindrical section 18, a second groove 6, a first cylindrical section 4, a first groove 5, and a second cylindrical section 17. The groove sides may include mating shoulders (not shown).

[0036] Figure 5 A Figures 1 to 4 of the first annulus 2 and two alignment rings 7, 8 is shown. Detail G shows that each of the alignment rings 7, 8 includes an alignment shoulder 21. These shoulders are arranged at the sides of the respective alignment rings. The alignment shoulders have a radial profile that is preferably straight, convex, concave, or of a complex geometry in order to meet the stability requirements implied by the shoulder position and the nominal dimensions of the components involved. The alignment shoulders are used to induce a stabilizing moment on the planetary member, the direction and magnitude of which urge the second axis to be more aligned with the first axis of symmetry.

[0037] Figure 6 A Figures 1 to 5The alignment rings 7, 8 engage corresponding grooves 5, 6 of one of the planetary members 3. The first cylindrical section 4 of the planetary member frictionally engages the inner / circumferential surface of the first annular gear 2, but the first sun gear is not shown. There are mating shoulders 22 on the flank surfaces of the first groove 5 and the second groove 6 to engage corresponding alignment shoulders 21 of the planetary member. The alignment shoulders and the mating shoulders cooperate to induce a stabilizing moment on the planetary member, the direction and magnitude of which urge the second axis to be more aligned with the first symmetry axis. Detail E shows that the flank surface of the first groove 5 includes the mating shoulder 22. Detail E also shows a curved crown 23 projecting from the circumferential surface of the first groove 5 towards the circumferential surface of the first alignment ring 7.

[0038] Typically, those skilled in the art are aware of curved crowns in the context of roller bearings (e.g., from published application EP 3748180 A1), but not in the context of reduction assemblies.

Claims

1. A mechanical speed reduction assembly, said mechanical speed reduction assembly comprising: a first sun gear (1), a first annular gear (2), the first annular gear being arranged concentrically around the first sun gear such that the first sun gear and the first annular gear share a first axis of symmetry (A), at least one hollow first planetary member (3), the at least one hollow first planetary member including a first cylindrical section (4), the first cylindrical section being in frictional engagement with the outer surface of the first sun gear and the inner surface of the first annular gear, the first planetary member being arranged to rotate about a second axis (B), wherein the first planetary member includes a circumferential first groove and a circumferential second groove (5, 6), the circumferential first groove and the circumferential second groove being spaced apart from each other by the first cylindrical section (4), the mechanical speed reduction assembly further comprising at least one first alignment ring (7, 8), the at least one first alignment ring being fixed to the first sun gear or the first annular gear to prevent movement along the first axis of symmetry (A), and the at least one first alignment ring projecting into the first groove or the second groove (5, 6).

2. The assembly according to claim 1, wherein the first alignment ring (7) includes an alignment shoulder (21), the alignment shoulder being arranged to engage with the groove side surface of the first groove or the second groove (5, 6), the groove side surface being generally perpendicular to the second axis (B).

3. The assembly according to claim 2, wherein the first groove and / or the second groove (5, 6) includes a mating shoulder (22), the mating shoulder being arranged to engage with the alignment shoulder (21).

4. The assembly according to any one of the preceding claims, wherein the first annular gear (1) includes a first recess (10), the first recess extending circumferentially around the first axis of symmetry (A), the first recess being arranged to partially receive the first alignment ring (7).

5. The assembly according to claim 4, wherein the first annular gear (1) includes a second recess, the second recess extending circumferentially around the first axis of symmetry (A) and being spaced apart from the first recess (10) along the first axis of symmetry, the second recess being arranged to partially receive the first alignment ring (7).

6. The assembly according to any one of claims 1 to 3, wherein the first sun gear (1) includes a first recess (10), the first recess extending circumferentially around the first axis of symmetry (A), the first recess being arranged to partially receive the first alignment ring (7).

7. The assembly according to claim 6, wherein the first sun gear (1) includes a second recess, the second recess extending circumferentially around the first axis of symmetry (a) and being spaced apart from the first recess (10) along the first axis of symmetry, the second recess being arranged to partially receive the first alignment ring (7).

8. The component according to claim 5 or 7, further comprising a second alignment ring (8) similar to the first alignment ring, the second alignment ring being partially arranged in the second recess.

9. The component according to claim 8, wherein the first alignment ring (7) engages with the first groove (5) and / or the second alignment ring (8) engages with the second groove (6).

10. The component according to any one of the preceding claims, wherein the first alignment ring (7), the second alignment ring (8), the first groove (10) and / or the second groove comprise a curved crown (23).

11. The component according to any one of the preceding claims, further comprising a second planet member (9) and a third planet member similar to the first planet member (3), the planet members being arranged around the first axis of symmetry (A), each of the second planet member and the third planet member being in frictional engagement with the outer surface of the first sun gear (1) and the inner surface of the first annular gear (2).

12. The component according to any one of the preceding claims, wherein at least the first planet member (3) comprises a second cylindrical section (17) similar to the first cylindrical section (4), and wherein the first groove (5) is arranged between the second cylindrical section and the first cylindrical section.

13. The component according to any one of the preceding claims, in particular according to claim 11 and / or 12, further comprising a second sun gear (11) and a second annular gear (12), the second annular gear being arranged concentrically around the second sun gear, wherein the second sun gear and the second annular gear share the first axis of symmetry (A), and wherein the second cylindrical section (17) is in frictional engagement with the outer surface of the second sun gear and the inner surface of the second annular gear.

14. The component according to claim 13, further comprising bearings (19, 20) arranged around the first axis of symmetry (A), wherein the bearings engage with the sun gear sides of the first sun gear (1) and the second sun gear (11), the sun gear sides being perpendicular to the first axis of symmetry.

15. The component according to claim 13 or 14, further comprising a third annular gear (14), wherein the first annular gear (2) is arranged between the second annular gear (13) and the third annular gear, and wherein at least the first planet member (3), in particular the third cylindrical section (18), is in frictional engagement with the inner surface of the third annular gear.

16. The component according to claim 15, wherein the second annular gear and the third annular gear are rotatably coupled.

17. A method of manufacturing a mechanical reduction component according to any one of the preceding claims, the method comprising: Step S1: inserting one of the alignment rings into one of the recesses of the first sun gear or the first annular gear, Step S2: Insert the alignment ring into at least the first groove or the second groove of the first planetary member. Step S3: Arrange the first sun gear relative to the first ring gear such that the first ring gear and the first sun gear are concentrically arranged and share the first axis of symmetry.

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