WO2015055155A2

WO2015055155A2 - Planet gear assembly

Info

Publication number: WO2015055155A2
Application number: PCT/CZ2014/000114
Authority: WO
Inventors: Remko GERBENZON; Raymond Hicks; Vilém ROŠKO
Original assignee: Wikov Industry A.S.
Priority date: 2013-10-16
Filing date: 2014-10-14
Publication date: 2015-04-23
Also published as: WO2015055155A3; GB201318325D0; WO2015055155A4

Abstract

A planet gear assembly (1) for use in a planetary gear box comprises a radially extending carrier plate (10), planet gears (20a, 20b) disposed on opposing sides of the carrier plate (10) and a spindle assembly (5) arranged to rotatably mount the planet gears (20a, 20b) on the carrier plate (10). The spindle assembly comprises: spindle members (30) disposed on opposing sides of the carrier plate (10), a bolt (40) extending through the carrier plate (10) and supporting both the first and second spindle members (30). First and second flexible members (50) are disposed on opposing sides of the carrier plate (10) and each respectively clamped between the first and second spindle members (30) and the carrier plate (10).

Description

PLANET GEAR ASSEMBLY

Field of the Invention

The present invention relates to a spindle assembly and to a planet gear assembly for use in a planetary gear box.

Background of the Invention

Planetary gear assemblies (also known as epicyclic gear boxes) are known and commonly used for example in renewable energy turbines, industrial speed increasing or reducing gearboxes and heavy vehicle drivelines and transmissions. In most applications there is a need for the gear assembly to be compact and/or lightweight.

It will be appreciated that planetary gear assemblies generally comprise a coaxial outer ring gear and central sun gear, with at least one (a typically a plurality of) planet gears which engage between the ring and sun gear. Since the planet gear(s) have an offset axis that are generally mounted on a carrier plate which extends substantially radially with respect to the axis of the gear assembly. The axis of the planet gear and the carrier/sun gear are generally parallel but it is known that some misalignment may occur in use (for example due to tolerances or loads, in particular torsional wind up of the carrier) which may undesirably increase gear or bearing loadings. In particular, many planetary gear assemblies utilise a multi-planet arrangement in which a plurality of circumferentially distributed planet gears are provided which share the load within the gear train and may enable an overall reduction in size and/or weight of the gear assembly. In such arrangements the correct meshing alignment of all the planet gears is important to enable effective load sharing between the planet gears.

One solution to these problems has been to mount the planet gears on a so called "flexible pin" such as that disclosed in US Patent 3,303,713. Such an arrangement mounts the gear on a flexible cantilever spindle member to provide a limited degree of compliant movement enabling the planet gear to correctly align. Advantageously, this helps equalise the load sharing in a multi- planet arrangement. An alternative to the "flexible pin" arrangement is disclosed in US Patent 4,700,583. In this patent a tubular compression member is utilised which is effective in reducing the overall length of the flexible pin assembly while allowing greater design freedom in determining the assembly stiffness and deflection characteristics.

Another approach to reduce the load sharing of a planetary arrangement is to provide a double row of planet gears (for example coaxial pairs of gears). This arrangement provides smaller facewidth gears in comparison to an equivalent single (wider) gear and improved load sharing by partially mitigating the effects of unwanted displacements and distortions in comparison to a wide single gear. Such an arrangement is, for example, shown in US Patent 7,297,086.

Another arrangement utilising pairs of coaxial planet gears is disclosed in US Patent 8,246,505 in which pairs of gears are supported on a shaft which is supported on a bogie plate on the planet carrier and is intended to allow for some misalignment between the planet carrier and the ring gear without negatively affecting the gear meshing.

However, known double row planet gear arrangements are still vulnerable to distortion and/or torsional windup under load which will cause unwanted misalignment of the gears. As with single row arrangements this will result in uneven mesh contacts and increase both gear and bearing loads.

Accordingly, embodiments of the invention seek to provide an alternative planetary gear arrangement which may, for example, further reduce the dimensions and/or weight of the assembly and/or increase its structural integrity and/or provide improved load sharing in a gear assembly.

Summary of Invention

According to a first aspect of the present invention there is provided a planet gear assembly for use in a planetary gear box, the gear assembly comprising;

a radially extending carrier plate; first and second paired pianet gears disposed on opposing sides of the carrier plate and mounted on a common axle; and a spindle assembly arranged to rotatably mount the planet gears on the carrier plate and to allow a limited degree of compliant movement of the planet gears under load, the spindle assembly comprising: first and second spindle members disposed on opposing sides of the carrier plate and each providing a bearing surface for supporting the first and second planet gears; a bolt extending through the carrier plate and supporting both the first and second spindle members; and first and second flexible members disposed on opposing sides of the carrier plate and each respectively clamped between the first and second spindle members and the carrier plate.

According to a further aspect the invention comprises spindle assembly arranged to rotatabiy mount a pair of planet gears on a carrier plate in a planetary gearbox and arrange to allow a limited degree of compliant movement of the planet gears under load, the spindle assembly comprising: first and second spindle members arranged to be disposed on opposing sides of the carrier plate and each providing a bearing surface for supporting a first and second planet gear;

a bolt extending through the carrier plate and supporting both the first and second spindle members; and

first and second flexible members disposed on opposing sides of the carrier plate and each arranged to be clamped between the first and second spindle members and the carrier plate.

It will be appreciated that the paired gears may typically be load sharing planet gears. It will be appreciated that the limited degree of compliant movement provided by the spindle assembly may allow the planet gear a predetermined degree of freedom of movement (for example in the radial direction and/or torsional about the axis of the spindle) to enable the planet gear to dynamically align within the planetary gear assembly.

Embodiments of the invention advantageously provide a spindle assembly having two halves projecting from either side of the carrier plate and each enabling independent compliant alignment of the associated planet gear. By mounting the planet gears in a flexible manner about a central carrier plate embodiments of the invention are advantageously able to substantially reduce or eliminate torsional distortions from the carrier and associated gear skewing. The provision of a single tension bolt extending through both halves of the spindle assembly is advantageously much less vulnerable to bending than a single cantilever bolt arrangement.

It will be appreciated that the two sides of the spindle assembly may typically be substantially identical (although one spindle member may be adapted to receive the head of the bolt whilst the other spindle member may be adapted to receive the opposing end of the bolt body). Thus, it will be appreciated that any features of the spindle assembly which are described herein as having "at least one" may typically comprise a pair of said features with one associated with each half of the spindle assembly (but in some embodiments could be provided on only one half of the spindle assembly). References to a half or halves of the spindle assembly will be understood to refer to the portion of the spindle assembly to one side of the carrier plate (i.e. which carrier one of the two planet gears).

The, or each, flexible member may be a tubular member. The, or each, flexible member may be coaxial with the spindle member.

The bearing surface is generally provided on the radially exterior surface of the spindle member. The spindle assembly may further comprise a bearing assembly on each bearing surface for supporting the planet gear.

The first and second spindle members may each extend from a base proximal to the carrier plate to a head distal to the carrier plate and wherein the bolt engages the head of each spindle member. Thus, the bolt may be arranged as a tension bolt which compresses the spindle assembly in the axial direction.

The base of at least one of the spindle member may be provided with a bearing face. The bearing face may abut a portion of the radial face of the carrier. The bearing face may be radially extending. The bearing face may include a seal. For example, a recess (for example an annular recess) may be provided on the bearing face for retaining a seal (for example an o-ring).

The carrier may comprise an axially extending protrusion on at least one side arranged to radially locate at least one of the spindle members. The axially extending protrusion may comprise an annular protrusion. The protrusion may surround the base of the spindle member. The protrusion may abut the radially outer surface of the spindle member. Alternatively, the protrusion may be spaced from the outer surface of the spindle member to aliow a limited degree of radial movement of the spindle member(for example by having a greater diameter than the outer diameter of the spindle member). By a radial clearance between the spindle member outer diameter and the protrusion the protrusion may act as an overload stop.

The protrusion may provide a radially extending surface arranged to abut a bearing face of the adjacent spindle members.

At least one of the spindle members is provided with a retaining nut to retain a bearing assembly on the outer surface thereof. The nut may be provided on the head of spindle member. The nut may be used to pre-load the bearing assembly. The bearing assembly may be radially clamped between the radially extending surface of the protrusion and the retaining nut.

At least one of the flexible members may have a reduced thickness central portion. The reduced thickness may be provided by a concave surface, for example a concave external surface, on the flexible member.

In some embodiments an intermediate member (for example a bush) may be provided which is seated between the external surface of the flexible member and an internal surface of the spindle member. The bush may extend axially inwardly of the spindle member and/or flexible member and may, for example, include a flange which acts as a bearing surface for the spindle member and/or flexible member.

The spindle member may have has an internal face at its head which opposes the carrier plate. The internal face may clamp the flexible member against the carrier plate. The internal face may be provided with an annular recess to receive the flexible member. The gear assembly may further comprise at least one radially extending support plate positioned axiaily externally to at least one of the planet gears. The gear assembly may comprise a pair of radially extending support plates, each positioned axiaily externally to one of the planet gears. The combination of carrier plate and one or two support plates provides a particularly high stiffness arrangement.

The at least one support plate may be connected to or integrally formed with the carrier plate to provide a carrier assembly.

The support plate and/or the carrier plate may be associated with an input.

The planet gear assembly may further comprise a plurality of paired planet gears distributed circumferentially about the carrier plate and each pair having an associated spindle assembly.

Whilst the invention has been described above extends to any inventive combination of features set out above or in the following description or drawings.

Brief Description of the Drawings

Specific embodiments of the invention will now be described in detail by way of example only and with reference to the accompanying drawings in which:

Figure 1 is a schematic cross sectional view of a detail of a planet gear assembly in accordance with a first embodiment of the invention; Figures 2A to 2C schematically show a planet gear assembly accordingo a first embodiment of the invention;

Figures 3A to 3C schematically show a planet gear assembly according to a second embodiment of the invention; and

Figures 4A to 4C schematically show a planet gear assembly according to a third embodiment of the invention.

Description of an Embodiment

Figure 1 shows a planet gear assembly 1 comprising a pair a load sharing planet gears 20a, 20b mounted on a carrier plate 10 by a spindle assembly 5. Each planet gear 20a, 20b has an external gearing which, in use, would engage both an outer ring gear and a central sun gear.

The carrier plate 10 extends in a generally radially direction within the gear assembly and the spindle assembly 5 extends from either side of the carrier plate 10 in a generally perpendicular direction relative to the plate (i.e. in general alignment with the axial direction of the gear assembly). It will be noted that the opposing halves of the spindle assembly 5 are substantially symmetrical. For clarity, like parts may be indicated on only one side of the spindle assembly in the figures but it will be noted that such features are shown on both sides of the carrier plate 10.

The spindle assembly comprises a pair of spindle members 30 which each support a bearing assembly 60 on to which the planet gears 20 are rotatably connected. In the illustrated embodiment the bearing assemblies 60 comprise paired tapered roller roller bearings (although the skilled person will appreciate that the choice of bearing arrangement will depend on the particular gearbox assembly). Each spindle member 30 is a generally tubular body with an open end proximal to the carrier plate 10 and a closed head 35 distal to the carrier plate 10. The base of the spindie members 30 are provided with a radially extending flange 34 which defines a radially extending bearing face 32. The bearing face 32 includes a recess 33 for retaining a sealing member, such as an o-ring, and abuts a radial face of the carrier 10. The seal provides a spindle oil seal which seals the cavity and enables the oil to reach the bearings without spilling out the clearance between spindle and carrier, but also allows the spindle to move.

The opposing, head 35 of the spindle member 30 is arranged to engage a boit 40 (with one head receiving the head of the bolt and the other engaging, for example threadingly engaging, the shaft of the bolt). The bolt 40 is coaxial with the spindle members 30 and extends through both spindle members 30 and passes through an aperture 18 in the carrier plate 10. It will be noted that the aperture 18 has a large clearance relative to the bolt 40 such that it does not constrain any movement of flex of the boit 40.

Clamped between each spindle member 30 and the carrier plate 10 is a flexible member 50 which comprises a tubular body and is coaxial with both the spindle member 30 and bolt 40. The distal end of the flexible member 50 is received in an annular recess 36 formed in the interior surface of the head 35 of the spindle member 30. The proximal end of the flexible member 50 is seated in a recess 14 in the carrier plate 10 such that it extends radially inwardly beyond the bearing face 32 of the spindle member 30. A central portion 54 of the flexible member 50 has a reduced cross sectional area with the flexible member having a concave outer surface.

The carrier plate 10 is provided with an axially extending angular protrusion 12 on each side. A bearing face 16 is provided within the protrusion for mating with the bearing face 32 of the spindle member 30. The protrusion 12 positions the spindle member on the carrier plate 10 and may delimit the radial displacement of the spindle member in use. The protrusion 12 is also provided with a radially extending outermost surface which is arranged to abut the bearing assembly on the adjacent spindle member 30 and the plane of which is substantially aligned with the axially outer plane of the flange 34 on the spindle member 30 so as to provide a continuous alignment surface for the bearings 60. A retaining nut 38 on the head 35 of the spindle member 30 may be used to retain and/or preload the bearing assembly 60 between the flange 34 (and protrusion 2) and the nut 38.

It will be appreciated that each half of the gear mounting arrangement of the invention may generally function in the manner described in US Patent 4,700,583 (the contents of which are incorporated herein by reference) but has the additional advantages of enabling the use of double planets (for example for power sharing). Advantageously, the arrangement of embodiments of the invention may provide a relatively stiffer arrangement which is less vulnerable to bending.

Figure 2 shows the carrier and support plate arrangement according to a first embodiment of the invention (with the cross section as shown in Figure 2A, a side section without the gears in Figure 2B and a three-dimensional perspective without the inclusion of the gears in Figure 2C). In this embodiment it will be noted that in addition to the carrier 10 there is also provided a radially extending support plate 82a and 82b on either side of the planet gear assembly. This provides a relatively stiff three-piece carrier assembly. As seen in Figures 2B and C the carrier plate 0 and support plates 82a and 82b are provided with cut-outs to accommodate the planet gears 20 and spindle assembly 5 and are rigidly connected to one another. Typically, one of the support plates is formed as part of an input 70 of the planetary gearbox. The other support plate 82 may forms part of a support 80.

In a similar manner Figure 3A illustrates an embodiment in which a single radially extending support plate 82' is provided on the external side of one of the planet gears 20a but no support plate is provided on the opposing external side of planet gear 20b. It will be appreciated that this arrangement would generally be less stiff than the arrangement of Figure 2 but could suitable for applications where space and/or weight is of greater concern. In this embodiment the support plate 82' is provided integrally with the input 70.

Figure 4 illustrates a further embodiment in which no additional support plates are provided and the carrier 10 is simply attached directly to an input 70. Again, this embodiment may be preferred in gearbox arrangements in which weight and/or space requirements are the primary design constraint.

It may also be noted that the embodiment of figure 4 shows a variant of the spindle assembly 5¹ which includes an intermediate member 56 positioned between the outer surface of the flexible member 50' and the inner surface of the spindle member 30'. The intermediate member 56 is a flanged bush. The intermediate member 56 extends radially inwardly of both the spindle member 30' and flexible member 50' and includes a flange 58 proximal to the carrier 10'. The flange 58 is disposed between the flexible member 50' and spindle member 30' and has an outwardly extending surface for receiving the end of the spindle member 30' proximal to the carrier and an inwardly extending surface for receiving the inner end of the flexible member 50'. It will be appreciated that the spindle assembly shown in either figure 1 or figure 4 may be interchangeable into any of the embodiments of the invention (i.e. the intermediate member 56 could be included or omitted in any embodiment depending upon the design characteristics of the gearbox and/or spindle assembly).

While the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

List of reference numbers

1 - planet gear assembly

5 - spindle assembly

10 - carrier p!ate

12 - protrusion

14 - recess

16 - bearing face

18 - aperture

20a - first planet gear

20b - second planet gear

30 - spindle member

32 - bearing face

33 - recess

34 - flange

35 - head

36 - annular recess 38 - nut

40 - bolt

50 - flexible member 54 - central portion 56 - intermediate member 58 - flange

60 - bearing assembly - input

- support

a - first support plateb - second support plate

Claims

A planet gear assembly for use in a planetary gear box, the gear assembly (1) comprising:

a radially extending carrier plate (10);

first and second paired planet gears (20a, 20b) disposed on opposing sides of the carrier plate (10) and mounted on a common axle; and

a spindle assembly (5) arranged to rotatably mount the planet gears (20a, 20b) on the carrier plate (10) and to allow a limited degree of compliant movement of the planet gears (20a, 20b) under load, the spindle assembly (5) comprising:

first and second spindle members (30) disposed on opposing sides of the carrier plate (10) and each providing a bearing surface for supporting the first and second planet gears (20a, 20b);

a bolt (40) extending through the carrier plate (10) and supporting both the first and second spindle members (30); and

first and second flexible members (50) disposed on opposing sides of the carrier plate (10) and each respectively clamped between the first and second spindle members (30) and the carrier plate (10).

2. A planet gear assembly as claimed in claim 1 , wherein the first and second spindle members (30) each extend from a base proximal to the carrier plate (10) to a head (35) distal to the carrier plate (10) and wherein the bolt (40) engages the head (35) of each spindle member (30).

3. A planet gear assembly as claimed in claim 2, wherein the base of at least one of the spindle members (30) is provided with a bearing face (32) which abuts a portion of the radial face of the carrier (10).

4. A planet gear assembly as claimed in any preceding claim, wherein the carrier (10) comprises an axially extending protrusion (12) on at least one side arranged to radially locate at least one of the spindle members (30).

5. A planet gear assembly as claimed in claim 4, wherein the, or each, protrusion (12) provides a radially extending surface arranged to abut a bearing face (32) of the adjacent spindle members (30).

6. A planet gear assembly as claimed in any preceding claim, wherein at least one of the spindle members (30) is provided with a retaining nut (38) to retain a bearing assembly (60) on the outer surface thereof.

7. A planet gear assembly as claimed in any preceding claim, wherein at least one of the flexible members (50) has a reduced thickness central portion (54). 8. A planet gear assembly as claimed in claim 7, wherein the reduced

thickness is provided by a concave external surface on the flexible member (50).

9. A planet gear assembly as claimed in any preceding claim, wherein spindle member (30) has an internal face at its head (35) which opposes the carrier (10) and clamps the flexible member (50) and, wherein, the internal face is provided with an annular recess (36) to receive the flexible member (50). 10. A planet gear assembly as claimed in any preceding claim, wherein the gear assembly (1) further comprises at least one radially extending support plate (82) positioned to the axially externally to at least one of the planet gears (20). 11. A planet gear assembly as claimed in claim 10, wherein the gear

assembly (1) comprises a pair of radially extending support plates (82a, 82b), each positioned axially externally to one of the planet gears (20a, 20b).

12. A planet gear assembly as claimed in claim 10 or 11 , wherein the at least one support plate (82) is connected to or integrally formed with the carrier plate (10) to provide a carrier assembly.

13. A planet gear assembly as claimed in any of claims 10 to 12, wherein the support plate (82) is associated with an input (70).

14. A planet gear as claimed in any preceding claim, wherein the carrier plate (10) is associated with an input (70).

15. A planet gear assembly as claimed in any preceding claim, further comprising a plurality of paired planet gears (20a, 20b) distributed circumferentially about the carrier plate (10) and each pair having an associated spindle assembly (5). 6. A spindle assembly arranged to rotatabiy mount a pair of planet gears (20a, 20b) on a carrier plate (10) in a planetary gearbox and arrange to allow a limited degree of compliant movement of the planet gears (20a, 20b) under load, the spindle assembly (5) comprising: first and second spindle members (30) arranged to be disposed on opposing sides of the carrier plate (10) and each providing a bearing surface for supporting a first and second planet gear (20a, 20b); a bolt (40) extending through the carrier plate (10) and supporting both the first and second spindle members (30); and first and second flexible members (50) disposed on opposing sides of the carrier plate (10) and each arranged to be clamped between the first and second spindle members (30) and the carrier plate (10).

17. A spindle assembly as claimed in claim 16, wherein the first and second spindle members (30) each extend from a base proximal to the carrier plate (10) in use to a head (35) distal to the carrier plate (10) in use and wherein the bo!t (40) engages the head (35) of each spindle member

(30).

18. A spindle assembly as claimed in claim 17, wherein the base of at least one of the spindle member (30) is provided with a bearing face (32) which, in use, abuts a portion of the radial face of the carrier (10).

19. A spindle assembly as claimed in any of claims 16 to 18, wherein at least one of the spindle members (30) is provided with a retaining nut (38) to retain a bearing assembly (60) on the outer surface thereof.

20. A spindle assembly as claimed in any of claims 16 to 19, wherein at least one of the flexible members (50) has a reduced thickness central portion (54).

21. A spindle assembly as claimed in claim 20, wherein the reduced thickness is provided by a concave external surface on the flexible member (50).

22. A spindle assembly as claimed in any of claims 16 to 21 , wherein

spindle member (30) has an internal face at its head (35) which opposes the carrier ( 0) and clamps the flexible member (50) in use and, wherein, the internal face is provided with an annular recess to receive the flexible member (50).

23. A planet gear assembly substantially as herein before described with reference to the description and accompanying figures. 24. A spindle assembly substantially as herein before described with

reference to the description and accompanying figures.