Compact gear reduction unit with a drive shaft that bears radial loads

Abstract

A compact gear reduction unit (1) of the type applying a transmission shaft subjected to radial loads, comprising a substantially box-like body (2) inside which a gear system (3) is housed for the transmission of the rotary motion from a drive shaft (4) to a transmission shaft (5), provided with an output reduction stage (7) of the planetary type. The output reduction stage (7) comprises a driving sun gear (8) rotating about a main axis (A) and an annular gear (9) associated integrally with the substantially box-like body (2), between which a plurality of planet gears (10) is engaged, supported by a transmission carrier (11) for the rotation about a respective longitudinal axis parallel to the main axis (A), which in turn rotates about the main axis and is associated so as to rotate integrally with the transmission shaft (5) at a connection region (12). The reduction unit (1) is further provided with a rolling device (14) adapted to support the radial loads associated with the transmission shaft (5) for the rotary guidance of the transmission shaft. The rolling device (14) comprises a first radial bearing (15) interposed between the substantially box-like body (2) and the carrier (11) in the radial direction and a second radial bearing (16) interposed radially between the body and the transmission shaft (5), the first and second bearings (15, 16) being arranged axially on opposite sides of the connection region (12).

Description

TECHNICAL FIELD

[0001] The present application relates to a compact gear reduction unit applying a transmission shaft which withstands radial loads. BACKGROUND

[0002] Known gear reduction units essentially comprise a housing for housing a gear system for transmitting rotation between a drive shaft and a transmission shaft.

[0003] In particular, reduction units are known whose gear system comprises at least one planetary output reduction stage constituted by a driving sun gear rotating about a main axis and by an annular gear integral with the housing, between which a plurality of planet gears are engaged, which rotate about their respective longitudinal axis, parallel to the main axis, by means of a transmission planet carrier which in turn rotates about said main axis and integrally with the transmission shaft.

[0004] If the reduction unit is of the multi-stage type, upstream of said planetary output reduction stage one or more planetary type and / or reduction stages with parallel axes in series can be provided.

[0005] The transmission shaft has at least one portion housed inside the housing, which is rotationally supported by suitable rolling members, such as a pair of bearings, each of which has an inner ring mounted on the transmission shaft and an outer ring housed in a corresponding seat formed in the housing. By means of an adjusting ring screwed onto the transmission shaft, it is possible to adjust the preloading of these bearings.

[0006] In particular, for this application, in which the transmission shaft not only withstands bending moments but also radial loads applied in a cantilevered manner, and generally two bearings with conical rollers mounted in an O-shaped configuration (so-called back-to-back configuration) are used.

[0007] Typically, a reduction unit with one or more planetary reduction stages of the type described above is applied in a rotary actuation system of a nacelle of a wind turbine, for example. In this case, the transmission shaft of the reduction unit is integrally rotating with a pinion which meshes with a toothed central bearing integral with said nacelle and in the coupling between said elements a radial load is generated which is applied to the transmission shaft.

[0008] According to the configuration of the components described above, the transmission shaft essentially has a portion housed inside the housing, along which an end region for coupling with the planet carrier, a region for coupling with said adjusting ring and a region for coupling with the two bearings can be determined in the axial direction.

[0009] This type of solution has some drawbacks, which include the fact that, according to the above-described configuration, the choice of the size of the longitudinal extension of the portion of the transmission shaft housed inside the casing, and, correspondingly, the choice of the size of the casing, cannot be reduced below certain values in order to avoid compromising the strength of the reduction unit, which is disadvantageous in terms of volume, weight and cost with respect to its performance.

[0010] In fact, as is known, the radial stresses that bearings with tapered rollers are able to withstand increase with the distance between them and decrease with the distance between the maximum bearing and the load application point in the bearing. For this reason, when choosing the size of the reduction unit, it is necessary to arrange one bearing adjacent to the load application point and the other at a distance sufficient to obtain the required support.

[0011] Therefore, as the cantilever radial load applied to the transmission shaft increases, the distance increases and, consequently, the length of the portion of the transmission shaft housed inside the casing and the longitudinal volume of the casing also increase. As a result, there is an increase in the longitudinal volume and the overall weight of the reduction unit, the production and logistics management costs of both the individual components (transmission shaft and casing) and the entire reduction unit are higher, the complexity of the assembly of the reduction unit intended to be applied in the machine increases and the amount of lubricating oil introduced in the casing to lubricate the moving components increases. SUMMARY

[0012] The aim of the present application is to eliminate the drawbacks of the background art, designing a compact gear reduction unit, which applies a transmission shaft that withstands radial loads, which allows to obtain a suitable rotational support of the transmission shaft even in the presence of radial loads applied in a cantilever manner and at the same time limits the longitudinal volume and the weight of the reduction unit.

[0013] Within this aim, the aim of the present application is to reduce the production and logistics management costs of the components and of the entire reduction unit.

[0014] Another aim of the present application is to reduce the amount of lubricating oil used in the reduction unit in order to further reduce the weight and the operating costs of the reduction unit.

[0015] Another aim of the present application is to make the reduction unit easier to apply and install inside complex machines that apply it.

[0016] Another aim of the present application is to make the reduction unit versatile in the application of transmission shafts that withstand cantilever radial loads, such as, for example, the rotational actuation units of wind turbine nacelles.

[0017] Another aim of the present application is to make the reduction unit have a structure that is simple, relatively easy to provide in practice, safe to use, effective to operate and relatively low in cost.

[0018] These objects and other purposes which will become more apparent hereinafter are all achieved by a compact gear reduction unit with a drive shaft subjected to radial loads, object of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0019] Further features and advantages of the present application will become more apparent from the detailed description of a preferred, but not exclusive, embodiment of a compact gear reduction unit with a drive shaft subjected to radial loads, illustrated by way of non-limiting example in the accompanying drawings, in which:

[0020] Figure 1 is a front view of a compact gear reduction unit with a drive shaft subjected to radial loads according to the present application;

[0021] Figure 2 is a sectional view of the reduction unit of Figure 1 taken along plane II-II;

[0022] Figure 3 is an exploded side view of a portion of the reduction unit according to the present application;

[0023] Figure 4 is a sectional view of Figure 3 taken along plane IV-IV;

[0024] Figure 5 is a perspective view of Figure 3 ;

[0025] Figure 6 is a perspective view of Figure 4 . DETAILED DESCRIPTION

[0026] With particular reference to the drawings, a compact gear reduction unit with a drive shaft subjected to radial loads is generally designated by the number 1.

[0027] The reduction unit 1 comprises a substantially box-like body 2 inside which a gear system 3 is housed for transmitting a rotary motion from a drive shaft 4 to a drive shaft 5.

[0028] In the illustrated embodiment, the substantially box-like body 2 comprises two half-shells 2a and 2b connected by threaded members 6. It is not excluded that the substantially box-like body 2 can be otherwise shaped and constituted by two or more components otherwise shaped and coupled to each other.

[0029] In use, the drive shaft 4 is adapted to be connected, directly or indirectly, to a rotary actuation device, such as a conventional electric or hydraulic motor.

[0030] The drive shaft 5 has an end portion which projects outside the substantially box-like body 2 and is adapted to transmit motion to a unit to be actuated in rotation.

[0031] In the embodiment shown, for example, the transmission shaft 5 is associated so as to rotate integrally with the toothed pinion 28 at an end portion designed to be coupled with a corresponding toothed member of the unit to be rotationally actuated for the transmission of movement. The pinion 28 is preferably formed integrally with the transmission shaft 5, but it is not excluded that they can be provided in two separate portions which rotate integrally about the main axis A at least by means of mechanical connection means.

[0032] The gear system 3 is provided with an output reduction stage 7 of the planetary type comprising a driving sun gear 8 rotating about the main axis A and an annular gear 9 associated integrally with the substantially box-like body 2 and extending about said axis. A plurality of planet gears 10 is engaged between the sun gear 8 and the annular gear 9 and is supported by a transmission carrier 11 so as to rotate about a respective longitudinal axis parallel to the main axis A, which in turn rotates about said main axis and is associated so as to rotate integrally with the transmission shaft 5 at a connection area 12.

[0033] The number and arrangement of the planet gears 10 can vary with respect to the size of the output reduction stage 7, which is optimal for a specific application. In the embodiment shown, four planet gears 10 are provided, which are angularly spaced apart at 90° about the main axis A.

[0034] In one possible embodiment, the gear system 3 is of the single-stage type. In this case, the output reduction stage 7 is directly interposed between the driving shaft 4 connected to the sun gear 8 and the transmission shaft 5 connected to the transmission carrier 11.

[0035] Alternatively, the gear system 3 can be of the multi-stage type. In this case, one or more reduction stages are arranged in series between the driving shaft 4 and the output reduction stage 7. Said further reduction stages can be of the planetary type or with parallel axes.

[0036] In the embodiment shown in the figures, the gear system 3 is of the multi-stage type and provides three further reduction stages 13a, 13b, 13c of the planetary type arranged in series between the driving shaft 4 and the output reduction stage 7.

[0037] The gear system 3 with the corresponding three further reduction stages 13a, 13b, 13c of the planetary type is not described in detail, since it is of the type known to the person skilled in the art.

[0038] In this case, the driving shaft 4 and the transmission shaft 5 are aligned along the main axis A. However, it is not excluded that the driving shaft 4 and the transmission shaft 5 can be parallel, but not aligned (if the gear system comprises one or more further reduction stages with parallel axes), i.e. at right angles or inclined to each other.

[0039] Furthermore, the reduction unit 1 comprises a rolling device 14 adapted to carry the radial loads associated with the transmission shaft 5 for the rotational guiding of the latter.

[0040] The rolling device 14 comprises a first radial bearing 15 interposed between the substantially box-like body 2 and the planet carrier 11 in the radial direction and a second radial bearing 16 interposed radially between the body and the transmission shaft 5, the first bearing 15 and the second bearing 16 being axially arranged on opposite sides of the connection area 12.

[0041] In the embodiment shown, the first bearing 15 and the second bearing 16 are of the type of radial bearings with tapered rollers mounted in an O-shaped configuration (so-called back-to-back configuration). Alternatively, they can be of the type of radial bearings with cylindrical rollers, radial needle bearings, radial spherical roller bearings, radial ring roller bearings or radial ball bearings, for example.

[0042] The particular arrangement of the first bearing 15 and the second bearing 16 allows to arrange the second bearing 16 adjacent to the area where the radial loads are applied and to maintain a sufficient distance between said bearings in the axial direction so as to obtain an optimal support of the transmission shaft 5, but with a reduction of the axial bulk of the transmission shaft and of the substantially box-like body 2 with respect to known solutions.

[0043] The planet carrier 11 of the output reduction stage 7 thus also cooperates in supporting the transmission shaft 5.

[0044] In greater detail, the planet carrier 11 comprises a flange 17 extending around the main axis A and for rotationally supporting a plurality of pivots 18 of the respective planet gears 10, which protrude in the axial direction on one side from the flange, and a hub 19 for connection to the transmission shaft 4, which protrudes on the other side, defining the connection area 12. In the embodiment shown, four pivots 18 are provided, which are angularly spaced apart at 90° around the main axis A.

[0045] A conventional bearing 29, for example of the roller type, is interposed between each pivot 18 and the corresponding planet gear 10.

[0046] The planet carrier 11 thus has a configuration known as pivots 18 with cantilevered support.

[0047] The hub 19 and the transmission shaft 5 are associated for integral rotation around the main axis A by means of a connection device provided at the connection area 12 having a spline profile 20. However, alternative methods of mechanical connection of the hub 19 to the transmission shaft 5 known to the person skilled in the art are not excluded.

[0048] A first bearing 15 is associated with the planet carrier 11 outside the flange 17. The inner ring of the first bearing 15 is keyed on the outer lateral wall of the flange 17.

[0049] The flange 17 is provided with an axial hole 21 which extends along the main axis A and is internally provided with an annular projection 22 which projects towards said axis.

[0050] The transmission shaft 5 is provided with an end handle 23 which is housed along the hole 21 and projects inside the substantially box-like body 2 beyond the projection 22.

[0051] There is also provided an adjustment ring 24 which is coupled to the handle 23 and is adapted to abut against the projection 22 in the axial direction in order to adjust the preloading of the bearings 15 and 16.

[0052] The ring 24 is internally threaded and engages with a corresponding female thread formed on the cylindrical lateral wall of the handle 23.

[0053] Furthermore, one or more rings 25 can be provided which have a calibrated thickness and are interposed in the axial direction between the ring 24 and the projection 22 in order to obtain the desired preloading of the bearings 15 and 16.

[0054] Furthermore, in the embodiment shown, there is a hydraulic seal device 26 of known type which is interposed in the radial direction between the hub 19 and the substantially box-like body 2 in order to insulate the portion of the internal cavity of the body which houses the gear system 3 and the first bearing 15 and in which the moving members are provided with oil for lubrication, and there is a Nilos type closing and sealing ring 27 which is clamped between the transmission shaft 5, the second bearing 16 and the substantially box-like body 2 in order to limit the portion of the internal cavity of said body which houses the second bearing 16 and in which the grease lubricant for the moving members is present.

[0055] It is not excluded that oil lubrication for all the moving members can be provided which is housed inside the substantially box-like body 2 and therefore the hydraulic seal device 26 can be shaped and positioned in other ways.

[0056] In particular, the reduction unit 1 can be applied in a unit (not shown) for the rotation actuation of a cabin around a vertical axis of the wind mast.

[0057] In this case, the reduction unit 1 comprises components of a complex machine and is installed with the main axis arranged vertically and with the pinion 28 arranged in the upper region and coupled with a toothed central bearing which is integral with the cabin to be rotationally actuated.

[0058] In this case, the radial load applied to the transmission shaft 5 originates from the reaction of the coupling between the pinion 28 and the central bearing.

[0059] However, in the application of providing a radial load to the transmission shaft 5, alternative uses of the reduction unit 1 are not excluded, such as units for the rotational actuation of a cab or accessories of a work vehicle, such as a basket, a crane, a concrete pump machine, a stationary cement mixer, a stationary crane, a mobile crane, a mixer truck, a slurry mixer, a mixer for a biogas plant, a mining machine, a crusher or a rolling mill.

[0060] In fact, it has been found that the described invention achieves the intended purposes and, in particular, it should be noted that the reduction unit according to the invention allows to obtain a proper rotational support of the transmission shaft even in the presence of radial loads and allows to include an axial extension of the transmission shaft, which is partially housed in the substantially box-like body and therefore of the reduction unit as a whole.

[0061] Therefore, compared to the known solutions, the reduction unit according to the invention also has a low weight and is therefore more easily usable and mobile, and also has lower production and operating costs and lower lubricating oil consumption.

[0062] Furthermore, the reduction unit according to the invention is versatile in use and can be configured and sized according to the requirements of the specific application.

[0063] The invention thus conceived can have many modifications and variants, all falling within the scope of the following claims.

[0064] All the details can be further replaced with other technically equivalent elements.

[0065] In fact, the materials used, as well as the contingent shapes and dimensions, can be any according to the requirements, without this entailing a departure from the scope of protection of the following claims.

[0066] This application claims the disclosure of Italian patent application No. 102019000020024 by way of reference.

[0067] In the case where, after a technical feature mentioned in any claim, a reference sign is mentioned, those reference signs are included only for the purpose of increasing the intelligibility of the claim and, therefore, the interpretation of each element identified by way of example with such reference signs does not have any limiting effect. CLAIM

Claims

1. A compact gear reduction unit (1) applied with a drive shaft that withstands radial loads, comprising: - a substantially box-like body (2), - a gear system (3) housed inside said substantially box-like body (2), - a drive shaft (4), - a drive shaft (5) having an end portion that projects outside said substantially box-like body (2) and is adapted to transmit motion to a unit to be rotationally actuated, - an output reduction stage (7) of the planetary type, comprising a driving sun gear (8) that rotates about a main axis (A) and an annular gear (9) that is integrally associated with said substantially box-like body (2), a plurality of planet gears (10) being engaged between said driving sun gear and said annular gear, said plurality of planet gears being supported for rotation about respective longitudinal axes parallel to said main axis (A) by a driving planet carrier (11) that in turn rotates about said main axis and is connected at a connection area (12) with said drive shaft (5) so as to rotate integrally, so that the rotation motion is transmitted from said drive shaft (4) to said drive shaft (5), and - a rolling device (14) comprising a first radial bearing (15) arranged so as to interpose in a radial direction between said substantially box-like body (2) and said planet carrier (11), and a second radial bearing (16) arranged so as to interpose radially between said substantially box-like body (2) and said drive shaft (5), said first radial bearing (15) and said second radial bearing (16) being arranged axially on opposite sides close to said connection area (12), so that said rolling device (14) is adapted to support radial loads exerted on said drive shaft (5) so as to achieve the rotation guidance of said drive shaft (5).

2. The reduction unit (1) according to claim 1, characterized in that Said planet carrier (11) comprises a flange (17) that extends about said main axis (A) and is used to rotationally support a plurality of pivots (18) of the respective planet gears (10), which project in an axial direction on one side from said flange, and a hub (19) used to connect to said drive shaft (5), which projects on the other side, defining said connection area (12).

3. The reduction unit (1) according to claim 2, characterized in that Said hub (19) and said drive shaft (5) are associated by a connection device having a spline profile (20) so as to rotate integrally about said main axis (A).

4. The reduction unit (1) according to claim 2, characterized in that Said first bearing (15) is associated with said planet carrier (11) outside said flange (17).

5. The reduction unit (1) according to claim 2, characterized in that Said flange (17) is provided with an axial hole (21) that extends along said main axis (A) and is internally provided with an annular projection (22) that projects towards said axis, and said drive shaft (5) comprises a shank (23) that is housed along said hole (21) and projects beyond said projection (22), an adjustment ring (24) being provided that is coupled to said shank (23) and is adapted to abut in an axial direction against said projection (22).

6. The reduction unit (1) according to claim 5, characterized in that The reduction unit comprises at least one ring (25) with calibrated thickness, interposed in the axial direction between the adjustment ring (24) and the protrusion (22).

7. The reduction unit (1) according to claim 2, characterized in that The reduction unit comprises a hydraulic seal (26) interposed in the radial direction between the hub (19) and the substantially box-shaped body (2) and arranged in the axial direction between the first bearing (15) and the second bearing (16).

8. The reduction unit (1) according to claim 2, characterized in that The reduction unit comprises a closing and sealing ring (27) clamped between the transmission shaft (5), the second bearing (16) and the substantially box-shaped body (2).

9. The reduction unit (1) according to claim 1, characterized in that The first bearing (15) and the second bearing (16) are alternatively of the type of radial bearing with tapered rollers mounted in O configuration, radial bearing with cylindrical rollers, radial needle bearing, radial spherical roller bearing, radial ring roller bearing, radial ball bearing.

10. The reduction unit (1) according to claim 1, characterized in that The transmission shaft (5) comprises a toothed pinion (28) that rotates integrally with the transmission shaft (5) around the main axis (A) and is arranged outside the substantially box-shaped body (2).

11. The reduction unit (1) according to claim 1, characterized in that The gear system (3) comprises at least one further reduction stage (13a, 13b, 13c) interposed between the drive shaft (4) and the output reduction stage (7), which is of the planetary type or of the type with parallel axes.

12. A rotationally actuated assembly for a nacelle of a wind turbine, characterized by, The assembly comprises a reduction unit (1) according to one or more of claims 1 to 11, wherein a corresponding pinion (28) can be functionally associated with a central bearing that rotates integrally with the cabin of the wind mast. The reduction unit comprises at least one ring (25) with calibrated thickness, interposed in the axial direction between the adjustment ring (24) and the protrusion (22). The reduction unit comprises a hydraulic seal (26) interposed in the radial direction between the hub (19) and the substantially box-shaped body (2) and arranged in the axial direction between the first bearing (15) and the second bearing (16). The reduction unit comprises a closing and sealing ring (27) clamped between the transmission shaft (5), the second bearing (16) and the substantially box-shaped body (2). The first bearing (15) and the second bearing (16) are alternatively of the type of radial bearing with tapered rollers mounted in O configuration, radial bearing with cylindrical rollers, radial needle bearing, radial spherical roller bearing, radial ring roller bearing, radial ball bearing. The transmission shaft (5) comprises a toothed pinion (28) that rotates integrally with the transmission shaft (5) around the main axis (A) and is arranged outside the substantially box-shaped body (2). The gear system (3) comprises at least one further reduction stage (13a, 13b, 13c) interposed between the drive shaft (4) and the output reduction stage (7), which is of the planetary type or of the type with parallel axes. The assembly comprises a reduction unit (1) according to one or more of claims 1 to 11, wherein a corresponding pinion (28) can be functionally associated with a central bearing that rotates integrally with the cabin of the wind mast.

Images