Mechanical Reduction Assembly

Abstract

The mechanical reduction assembly includes a first sun wheel and a first ring wheel concentrically disposed about the first sun wheel. The first sun wheel and the first ring wheel share a first axis of symmetry. The assembly includes at least a first hollow planetary member having a first cylindrical portion frictionally engaged with the outer circumferential surface of the first sun wheel and the inner circumferential surface of the first ring wheel. The first planetary member is arranged to rotate about a second axis. The first planetary member has a first circumferential groove and a second circumferential groove. The first groove and the second groove are spaced apart by the first cylindrical portion. The assembly further includes at least a first alignment ring. The first alignment ring is fixed to the first sun wheel or the first ring wheel and protrudes toward the first groove or the second groove to resist movement along the first axis of symmetry.

Description

[Technical Field]

[0001] The present invention relates to a mechanical reduction assembly comprising a plurality of rotationally symmetrical members and a method for assembling said mechanical reduction assembly. The proposed mechanical reduction assembly is suitable for changing the magnitude or direction of an output rotational speed relative to an input rotational speed depending on which of the member(s) receives an input torque. [Background technology]

[0002] Patent Document 1 discloses a compound planetary friction drive including a first sun wheel and a planet wheel. The first sun wheel is engaged with the planet wheel. The planet wheel is arranged to have two outer portions having a first radius and a central portion having a second radius, which is different from the first radius. A transition region is provided between the outer portion and the central portion. An outer ring annulus and a central ring annulus are provided. The outer ring annulus and the central ring annulus are in driving engagement with the planet wheel. The outer ring annulus has two portions. A central ring annulus is disposed between the two portions along the length of the planet gear. The first sun wheel is in frictional engagement with the outer portion of the planet wheel. The outer portion of the planet wheel is in frictional engagement with a portion of the outer ring annulus. The central ring annulus is in frictional engagement with the central portion of the planet wheel. The planet wheel is hollow and continuously compressible along its entire length through the outer portion, transition region, and central portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 178380 Summary of the Invention [Problem to be solved by the invention]

[0004] It can be seen that the problem to be solved is to provide an improved mechanical reduction assembly. [Means for solving the problem]

[0005] This problem is solved by a mechanical reduction assembly according to claim 1 and by preferred embodiments according to the respective dependent claims. A first embodiment of the mechanical reduction assembly according to the present invention includes a first sun wheel and a first ring wheel. The first ring wheel is concentrically disposed with the first sun wheel, so that the first sun wheel and the first ring wheel share a first axis of symmetry. The assembly further includes at least one hollow first planetary member. The first planetary member has a first cylindrical portion. The first cylindrical portion is in frictional engagement with the outer peripheral surface of the first sun wheel and the inner peripheral surface of the first ring wheel. The first cylindrical portion serves as a running surface for the first planetary member. The first planetary member is arranged to rotate about a second axis. The first planetary member has a first circumferential groove and a second circumferential groove. The first groove and the second groove are separated from each other by the first cylindrical portion. The assembly further includes at least a first alignment ring. The first alignment ring is fixed to the first sun wheel or the first ring wheel to resist movement along the first axis of symmetry, and the first alignment ring protrudes toward the first groove or the second groove. [Effects of the Invention]

[0006] An alignment ring that is secured against movement along the first axis of symmetry can act to resist undesired movement of the first planet along the first or second axis because the alignment ring protrudes toward the first or second groove, which can be beneficial for reducing slippage and / or wear caused by relative rotation of the first planet, particularly during operation of the assembly.

[0007] In the prior art, the planets are often constrained by axle and cam systems to achieve alignment of the planets with the sun wheel and ring wheel. In the prior art, an alignment mechanism may serve to align the output member of the assembly with the rotational axis of the planets.

[0008] The first planetary member of the present invention is capable of moving and rotating about two or more axes. The second axis of the planetary member is not fixed relative to the first axis of symmetry. The output member of the assembly may be fixed by an external bearing. An alignment ring may facilitate further alignment of the second axis relative to the first axis of symmetry. The first alignment ring may provide a thrust bearing surface for applying thrust to the first planetary member. This may facilitate further alignment of the second axis relative to the first axis of symmetry.

[0009] Furthermore, for a given amount of compressive force applied to the contact surfaces, a certain amount of tractive "thrust" is available, determined by the coefficient of friction. Any amount of skewness causes the tractive thrust to be vectored, creating an "angle" that is non-parallel to the desired line of motion. Any component of the vector that is not parallel to the allowed line of motion is lost. If the assembly is constrained against axial motion, the components must slip axially. Because the coefficient of friction during slip is lower than during tractive slip, additional losses occur. At certain skew angles, the assembly can rapidly lose traction. Modifying the shape and position of the first alignment ring can counteract this critical skew angle. Reducing the amount of lost thrust increases the torque capacity and efficiency of the assembly. Reducing the amount of slip can reduce wear on the assembly's components, thereby extending the assembly's lifespan. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 shows a cross section (left side) of an exemplary embodiment of a mechanical reduction assembly. [Figure 2] FIG. 2 shows a cross section of another exemplary embodiment. [Figure 3] FIG. 3 shows a side view of an exemplary embodiment identical to FIG. [Figure 4] FIG. 4 shows a cross section of one of the planet members 3 in the embodiment shown by FIGS. [Figure 5] FIG. 5 shows the first ring wheel 2 and the two alignment rings 7, 8 of FIGS. [Figure 6] FIG. 6 shows the alignment rings 7, 8 of FIGS. 1 to 5 engaged with respective grooves 5, 6 of one of the planet members 3. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred Embodiment The preferred embodiments described below and in the respective dependent claims can be beneficially combined unless otherwise specified.

[0012] The assembly may be a single-stage planetary reduction assembly. The at least one first planet member may be supported by a planet carrier. The assembly may be part of a larger multi-stage planetary reduction assembly.

[0013] In one embodiment, the first alignment ring includes an alignment shoulder. The alignment shoulder is positioned to engage a groove side surface of the first or second groove. The groove side surface is generally perpendicular to the second axis. The alignment shoulder provides a stabilizing moment to the planet member with a direction and magnitude that promotes further alignment of the second axis with the first axis of symmetry. The alignment shoulder may be a mechanical flange or shoulder. The radial profile of the alignment shoulder is preferably linear, convex, concave, or complex, thereby meeting the stability requirements implied by the shoulder location and the nominal dimensions of the components. The alignment shoulder may extend from a side surface of the first alignment ring. The side surface is perpendicular to the first or second axis.

[0014] In one embodiment, the first groove and / or the second groove includes a mating shoulder that is positioned to engage with the alignment shoulder. The mating shoulder may be shaped to complement the alignment shoulder. A larger or smaller contact angle can provide a larger or smaller stabilizing force. The profile of the mating shoulder may be identical to the profile of the alignment shoulder. Alternatively, the profile of the mating shoulder may be modified to allow for manufacturability. The radial profile of the mating shoulder is preferably linear, convex, concave, or a compound shape. This allows for stability requirements implied by the shoulder location and the nominal dimensions of the component.

[0015] In another embodiment, the first ring wheel includes a first recess extending circumferentially about a first axis of symmetry. The first recess is arranged to partially receive the first alignment ring. Preferably, the first ring wheel includes a second recess extending circumferentially about the first axis of symmetry and spaced apart from the first recess along the first axis of symmetry. The second recess is arranged to partially receive the first alignment ring. The first alignment ring can be secured within the recess against rotation relative to the first ring wheel.

[0016] In a further embodiment, the first sun wheel comprises a first recess extending circumferentially around the first axis of symmetry. The first recess is arranged to partially receive the first alignment ring. Preferably, the first sun wheel comprises a second recess extending circumferentially around the first axis of symmetry and spaced apart from the first recess along the first axis of symmetry. The second recess is arranged to partially receive the first alignment ring. The first alignment ring may be secured within the recess against rotation relative to the first sun wheel.

[0017] Some embodiments include a second alignment ring similar to the first alignment ring. The second alignment ring may be partially disposed within the second recess. Preferably, the first alignment ring is engaged with the first groove and / or the second alignment ring is engaged with the second groove.

[0018] According to another embodiment, the first alignment ring, the first recess, and / or the second recess include a curved crown. The curved crown may be defined by a portion of a circle, an ellipse, or a portion of a logarithmic curve, preferably having a radius in the range of 0.025 mm to 25.4 mm. The curved crown of the first alignment ring may extend toward the circumferential surface of the first recess or the second recess, or toward the groove side surface of the first groove or the second groove. Alternatively or additionally, the curved crown of the first groove or the second groove may extend toward the circumferential surface of the first alignment ring or protrude from one of the groove side surfaces to engage with the side surface of the first alignment ring. The curved crown may extend circumferentially around the first axis of symmetry or may extend circumferentially 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. Each of these planetary members is in frictional engagement with the outer peripheral surface of the first sun wheel and the inner peripheral surface of the first ring wheel. In particular, the fourth planetary member and further planetary members, similar to the first planetary member, can contribute to reducing the torque transmitted by each of these planetary members. This embodiment can function as a single reduction assembly. The proposed mechanical reduction assembly is suitable for increasing the input rotational speed depending on which member(s) of the assembly receives the input torque.

[0020] In a preferred embodiment, at least the first planetary member includes a second cylindrical portion similar to the first cylindrical portion. The first groove or the second groove is disposed between the second cylindrical portion and the first cylindrical portion. At least the first planetary member may include a third cylindrical portion similar to the first cylindrical portion. The first cylindrical portion, the second cylindrical portion, and the third cylindrical portion 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, the two cylindrical portions may be machined separately before being joined. One or more of the grooves may be machined and converted into the first planetary member by a lathing step.

[0021] Another embodiment further includes a second sun wheel and a second ring wheel concentrically disposed with the second sun wheel. The second sun wheel and the second ring wheel share a first axis of symmetry. The second cylindrical portion frictionally engages the outer circumferential surface of the second sun wheel and the inner circumferential surface of the second ring wheel. The proposed mechanical reduction assembly is suitable for increasing the input rotational speed depending on which member of the assembly receives the input torque. One of the sun wheels, preferably the second sun wheel, may be rotatably fixed during operation of the embodiment.

[0022] Some embodiments further include bearings disposed about the first axis of symmetry. The bearings engage with the sun wheel side surfaces of the first sun wheel and the second sun wheel. The sun wheel side surfaces are perpendicular to the first axis of symmetry. The bearings can contribute to reducing the vibration of the sun wheels. The bearings can contribute to stabilizing the first sun wheel during operation in some embodiments. The bearings can be roller bearings or needle bearings.

[0023] A further embodiment further includes a third ring wheel. The first ring wheel is disposed between the second ring wheel and the third ring wheel. At least the first planetary member, particularly the third cylindrical portion, is frictionally engaged with the inner surface of the third ring wheel. This embodiment may also include a third sun wheel. The outer peripheral surface of the third sun wheel is frictionally engaged with at least the first planetary member, particularly the third cylindrical portion of the first planetary member. The first sun wheel is disposed between the second sun wheel and the third sun wheel. A bearing may further be provided between the third sun wheel and the first sun wheel, thereby allowing the first sun wheel to rotate relative to the third sun wheel. The planetary member(s) in this embodiment may include a third cylindrical portion, a second groove, a first cylindrical portion, a first groove, and a second cylindrical portion. One or more of the groove side surfaces may include a mating shoulder(s). This embodiment may function as a two-stage planetary reduction assembly.

[0024] Preferably, the second ring wheel and the third ring wheel are rotatably connected (coupled) to each other, and these connected ring wheels can function as torque output members in this embodiment.

[0025] The method for manufacturing the above-mentioned mechanical reduction assembly (second aspect) preferably comprises the following steps: Step S1: inserting one of a plurality of alignment rings into one of a plurality of recesses of a first sun wheel or a first ring wheel; a step S2 of inserting an alignment ring into at least the first groove or the second groove of the first planetary member; Step S3 of positioning the first sun wheel relative to the first ring wheel such that the first ring wheel and the first sun wheel are concentrically arranged and share a first axis of symmetry; Contains:

[0026] Exemplary Embodiments Further details and advantages of the invention will become apparent to those skilled in the art from the exemplary embodiments described below.

[0027] FIG. 1 shows a cross-section (left side) of an exemplary embodiment of a mechanical reduction assembly. The assembly includes a first sun wheel 1 and a first ring wheel 2 concentrically disposed about the first sun wheel, such that the first sun wheel and the first ring wheel share a first axis of symmetry A. The assembly also includes at least a hollow first planetary member 3. The first planetary member 3 has a first cylindrical portion 4 that frictionally engages the outer circumferential surface of the first sun wheel and the inner circumferential surface of the first ring wheel. The first planetary member is arranged to rotate about a second axis B. The first planetary member includes a first circumferential groove 5 and a second circumferential groove 6. The first groove and the second groove are separated from each other by the first cylindrical portion. The assembly also includes at least a first alignment ring 7. The first alignment ring is fixed to the first ring wheel to resist movement along the first axis of symmetry and protrudes toward the first groove. While only two planetary members 3 and 9 are shown, this embodiment includes at least a third and fourth planetary member (not shown) having a similar structure. Additionally, this embodiment includes a second alignment ring 8. The second alignment ring is also fixed to the first ring wheel against movement along the first axis of symmetry and protrudes toward the second groove. Each of the alignment rings is partially held within a respective recess in the first ring wheel. The recess is shown on the right side of FIG. 1.

[0028] FIG. 2 shows a cross section of another exemplary embodiment. In addition to the components shown in FIG. 1, this embodiment further includes second and third sun wheels 11 and 12, second and third ring wheels 13 and 14, at least a second planetary member 15, and a second alignment ring 16 similar to the first alignment ring. The first and second alignment rings 7 and 8 are fixed to the first ring wheel to resist movement along a first axis of symmetry and engage with first and second grooves in the respective planetary members. Each of the alignment rings is partially held within a respective recess in the first ring wheel 2. Each of the planetary members includes a second cylindrical portion 17 and a third cylindrical portion 18. As shown, each of the first and second grooves is located between two of the cylindrical portions. Despite the presence of the grooves, each of the planetary members has a single-piece hollow structure.

[0029] The first cylindrical portion 4 is in frictional engagement with the outer circumferential surface of the first sun wheel 1 and the inner circumferential surface of the first ring wheel 2. The second cylindrical portion 17 is in frictional engagement with the outer circumferential surface of the second sun wheel 11 and the inner circumferential surface of the second ring wheel 13. The third cylindrical portion 18 is in frictional engagement with the outer circumferential surface of the third sun wheel 12 and the inner circumferential surface of the third ring wheel 14. While only two planetary members are shown, this embodiment includes at least a third planetary member and a fourth planetary member. A first bearing 19 is located between the first and second sun wheels. A second bearing 20 is located between the first and third sun wheels.

[0030] This embodiment may be operated such that the first sun wheel is driven. The first ring wheel is fixed against rotation. The second and third sun wheels are allowed to rotate freely. The second and third ring wheels are rotatably connected and function as a combined output member. The second and third cylindrical portions of the planetary members drive the second and third ring wheels to rotate about a first axis of symmetry while the first cylindrical portion of the planetary members rolls along the inner surface of the first ring wheel. Operating in this manner, the assembly functions as a two-stage reduction assembly.

[0031] Figure 3 shows a side view of an exemplary embodiment identical to Figure 2. This embodiment comprises ten hollow planets 3 arranged around a first axis of symmetry A. Each of these planets transmits a portion of the total torque between the sun wheel and the corresponding ring wheel.

[0032] Figure 4 shows a cross section of one of the planet members 3 in the embodiment shown in Figures 2 and 3. The planet member comprises (from left to right) a third cylindrical portion 18, a second groove 6, a first cylindrical portion 4, a first groove 5, and a second cylindrical portion 17. The groove sides may have mating shoulders (not shown).

[0033] FIG. 5 shows the first ring wheel 2 and the two alignment rings 7 and 8 of FIGS. 1 to 4. Detail G shows that each of the alignment rings 7 and 8 has an alignment shoulder 21. These shoulders are located on the side of the respective alignment ring. The alignment shoulders preferably have a linear, convex, concave, or compound radial profile, which satisfies the stability requirements implied by their location and the nominal dimensions of the components. The alignment shoulders serve to provide a stabilizing moment on the planets with a direction and magnitude that promotes further alignment of the second axis with respect to the first axis of symmetry.

[0034] FIG. 6 shows the alignment rings 7, 8 of FIGS. 1-5 engaged with respective grooves 5, 6 of one of the planetary members 3. The first cylindrical portion 4 of the planetary member frictionally engages the inner / circumferential surface of the first ring wheel 2 (not shown). The first groove 5 and second groove 6 have mating shoulders 22 on their groove sides that engage with respective alignment shoulders 21 of the planetary members. The alignment and mating shoulders cooperate to provide a stabilizing moment on the planetary member with a direction and magnitude that promotes further alignment of the second axis with the first axis of symmetry. Detail E shows that the groove sides of the first groove 5 have mating shoulders 22. Detail E also shows a curved crown 23 that projects from the circumferential surface of the first groove 5 toward the circumferential surface of the first alignment ring 7.

[0035] Curved crowns are generally known to those skilled in the art in the context of roller bearings, for example, due to the existence of published application EP3748180A1, but curved crowns in the context of reduction assemblies are not.

Claims

1. 1. A mechanical reduction assembly comprising: a first sun wheel (1); a first ring wheel (2) arranged concentrically with the first sun wheel; and at least a hollow first planetary member (3), The first sun wheel and the first ring wheel share a first axis of symmetry (A); The first planetary member has a first cylindrical portion (4), the first cylindrical portion is in frictional engagement with an outer peripheral surface of the first sun wheel and an inner peripheral surface of the first ring wheel; the first planetary member is arranged to rotate about a second axis (B); the first planetary member has a first circumferential groove and a second circumferential groove (5, 6); the first groove and the second groove are separated from each other by the first cylindrical portion (4); The assembly further comprises at least a first alignment ring (7, 8); an assembly in which the first alignment ring is fixed to the first sun wheel or the first ring wheel so as to oppose movement along the first axis of symmetry (A) and protrudes towards the first groove or the second groove (5, 6).

2. The first alignment ring (7) has an alignment shoulder (21); the alignment shoulder is arranged to engage with a groove side surface of the first groove or the second groove (5, 6); The assembly of claim 1 , wherein the groove sides are generally perpendicular to the second axis (B).

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

4. the first ring wheel (2) has a first recess (10) extending circumferentially around the first axis of symmetry (A); 4. An assembly according to any one of claims 1 to 3, wherein the first recess is arranged to partially receive the first alignment ring (7).

5. The first ring wheel (2) has a second recess, the second recess extends circumferentially around the first axis of symmetry (A) and is spaced apart from the first recess (10) along the first axis of symmetry; 5. An assembly according to claim 4, wherein the second recess is arranged to partially receive the first alignment ring (7).

6. the first sun wheel (1) has a first recess (10) extending circumferentially around the first axis of symmetry (A); 4. An assembly according to any one of claims 1 to 3, wherein the first recess is arranged to partially receive the first alignment ring (7).

7. The first sun wheel (1) has a second recess, the second recess extends circumferentially around the first axis of symmetry (A) and is spaced apart from the first recess (10) along the first axis of symmetry; 7. An assembly according to claim 6, wherein the second recess is arranged to partially receive the first alignment ring (7).

8. The assembly further comprises a second alignment ring (8) similar to the first alignment ring; The assembly of claim 5 or 7, wherein the second alignment ring is partially disposed within the second recess.

9. The first alignment ring (7) is engaged with the first groove (5); and / or 9. The assembly of claim 8, wherein the second alignment ring (8) is engaged with the second groove (6).

10. 10. The assembly according to any one of claims 1 to 9, wherein the first alignment ring (7), the second alignment ring (8), the first recess (10), and / or the second recess have a curved crown (23).

11. The assembly comprises: Further comprising a second planetary member (9) and a third planetary member similar to the first planetary member (3), the second planetary member and the third planetary member are arranged around the first axis of symmetry (A); 11. The assembly according to claim 1, wherein the second planetary member and the third planetary member are in frictional engagement with an outer peripheral surface of the first sun wheel (1) and an inner peripheral surface of the first ring wheel (2), respectively.

12. At least the first planetary member (3) has a second cylindrical portion (17) similar to the first cylindrical portion (4), Assembly according to any one of the preceding claims, wherein the first groove (5) is located between the second cylindrical portion and the first cylindrical portion.

13. The assembly comprises: a second sun wheel (11); a second ring wheel (13) arranged concentrically with the second sun wheel; the second sun wheel and the second ring wheel share the first axis of symmetry (A); Assembly according to any one of claims 1 to 12, in particular claims 11 and / or 12, wherein the second cylindrical portion (17) is in frictional engagement with the outer circumferential surface of the second sun wheel and with the inner circumferential surface of the second ring wheel.

14. The assembly further comprises bearings (19, 20) arranged around the first axis of symmetry (A), The bearing engages with a sun wheel side surface of the first sun wheel (1) and a sun wheel side surface of the second sun wheel (11), The assembly of claim 13 , wherein a sun wheel side surface of the first sun wheel and a sun wheel side surface of the second sun wheel are perpendicular to the first axis of symmetry.

15. The assembly further comprises a third ring wheel (14); The first ring wheel (2) is disposed between the second ring wheel (13) and the third ring wheel; Assembly according to claim 13 or 14, wherein at least the first planet member (3), in particular the third cylindrical portion (18), is in frictional engagement with the inner surface of the third ring wheel.

16. 16. The assembly of claim 15, wherein the second ring wheel and the third ring wheel are rotatably connected.

17. 17. A method of manufacturing a mechanical reduction assembly according to any one of claims 1 to 16, comprising the steps of: Step S of inserting one of a plurality of alignment rings into one of a plurality of recesses of the first sun wheel or the first ring wheel. １ and, Step S of inserting the alignment ring into at least the first groove or the second groove of the first planetary member. ２ and, Step S of positioning the first sun wheel relative to the first ring wheel such that the first ring wheel and the first sun wheel are concentrically disposed and the first ring wheel and the first sun wheel share the first axis of symmetry. ３ and, The method includes:

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